Expertise in buildings with a focus on Corona

 

What can you do to improve the situation and reduce the risk of infection?

Disclaimer

This document has been compiled with great care by a number of members of the FHI Building Automation trade association. Given the uncertainty surrounding COVID-19, it is important to recognize that the authors and publisher of this document are not liable or responsible for the consequences of applying or not applying the measures mentioned here.

 

RESUME

BUILT ENVIRONMENT AND CORONA

CONTAMINATION and ROUTES OF TRANSMISSION

RECOMMENDED ACTIONS

 GLOSSARY.

WHAT TO DO?

WHEN IS A BUILDING SAFE?

FROM THEORY TO PRACTICE PER MEASURE

Adjust ventilation quantities

Adjust ventilation operating times.

Set continuous ventilation mode.

Opening windows

Ventilation and use of space.

Toilet ventilation. 

Sanitary hygiene

Prevent recirculation (central)

Check heat recovery equipment

Fan coil units and ceiling induction units, (recirculation locally) 

Heating, Cooling and possible humidification setpoints

Cleaning channels

What to do with air filters.

Indoor air quality monitoring and other GBS data

1. SUMMARY

 

Various techniques are used within buildings to offer users a desired climate and appropriate functionality. The COVID-19 pandemic has drawn attention to the importance of ventilation. The role of ventilation systems is primarily aimed at maintaining oxygen levels. It is now a general trend that the spread of the virus is limited by good ventilation.

 

However, the question in society is broader: Is our building safe and are workplaces safe to use?

 

This document takes a structural look at the entire context of the built environment. The generic images surrounding contamination, transition routes and recommended measures are important. Healthcare expertise is a different field. The focus in this document is on theoretical advice for the built environment and converting this into practical implementation.

 

Based on a quick scan (chapter 6), a professional can recommend actions and practical steps per measure. This document contains detailed advice, which is mainly aimed at the (technical) professionals who set up, adapt or manage the (technical) facilities.

 

All measures must be put into operation in an orderly manner, checked for proper functioning and, where necessary, extensively functionally tested. Changes in design and principles must be properly recorded in logbooks and revision documents. Users must be properly instructed.

 

In addition to the expert use of technical systems in a building, generally recommended measures (for example keeping your distance and staying at home if you suspect contamination) must be properly followed and communicated.

 

Many factors play a role and there are many different types of (functions of) buildings, so it is not possible to clearly determine whether a building (corona) is safe. With the help of the quick scan (chapter 6) and an action plan, an initial inventory can be made of the measures to be taken. For the technical installations, a professional can then provide advice on taking measures in the building, with an emphasis on the following fifteen possible measures:

 

Adjust ventilation quantities

Adjust ventilation operating times

Set continuous ventilation mode

Opening windows

Ventilation and use of space

Toilet ventilation

Sanitary hygiene

Prevent recirculation (central)

Check heat recovery equipment

Fan coil units and ceiling induction units, (recirculation locally)

Heating, Cooling and possible humidification setpoints

Cleaning channels

What to do with air filtration?

Indoor air quality monitoring and other GBS data.

Smarter use of the available data in the Building Management System and Apps

 

These measures are described in detail in Chapter 8.

2. BUILT ENVIRONMENT AND CORONA

 

After the necessary (scientific) discussions and research regarding the spread of viruses within buildings, the COVID-19 pandemic has drawn attention to the role of ventilation systems in this. Ventilation's primary function is to maintain the oxygen level and to remove waste air (CO₂) and "odors". In the context of Corona, an additional function is added and that is the “dilution” of potentially infectious air and its removal.

 

Although initially not all experts and virologists were (completely) convinced of the contagiousness of aerosol spread, the general trend is that with this spread in aerosol form, where the virus particles carry further and the infected air has a much greater reach, a good and efficient ventilation is important. The RIVM also indicates that good ventilation, especially in rooms where many people are present for a longer period of time, can make a substantial contribution to limiting contamination. It should be noted that ventilation is certainly not the holy grail, but that behavioral measures regarding keeping your distance and staying at home in the event of (suspected) infection are also important.

 

Various agencies and experts have now given and are providing all kinds of advice to limit the spread of the virus as well as measures to return to a workable situation in the workplace.

Questions arise for many employers and employees: Is our building safe? Are the workplaces safe to use? What do we need to do to be able to work safely again? The answers to this are not unanimous and depend heavily on the nature of the work, the occupancy of the building and the nature of the people (age, health, etc.). A school faces different challenges than an office or theater.

 

In the Netherlands, the scheme involves a lot of national communication regarding behavior based on the advice of the RIVM and the Outbreak Management Team (OMT). There are several organizations and interest groups that have their say regarding the technical aspects. In addition to advice on behavior, they also provide guidelines on how to deal with the technical installations. For example, there is the Corona Expert Panel, a partnership of TNO, VCCN, TUe and Royal HaskoningDHV, and, for example, TVVL and inclimate.nl. ASHREA and REHVA have made themselves heard internationally.

 

The measures indicated generally contain the same action points. The advice primarily concerns measures regarding behavior such as keeping sufficient distance and regarding the installation for ventilation, both centrally and decentrally. The advice is formulated in general terms so that it can be understood by 'everyone' and is based on scientific research.

 

These advices in themselves are generally good, but also very theoretical. A lack is felt in being able to practically implement the advice. With the help of expert parties and who are they? Furthermore, the advice primarily concerns the (mechanical) air distribution technology. However, no indoor climate installation is possible without an integral measuring and control installation or a building management system (BMS). So we have to ask ourselves the question; How do we make the step from theoretical advice to practical implementation?

Since not everything is still known about the spread and contagiousness of the virus, it is difficult and partly impossible to impose clear and quantified requirements on a building and building installations for a specific use. The basic principle is that matters that cannot yet be ruled out must be taken into account. Well-considered and proportionate (subjective) measures must be taken.

 

The measures may be situation specific and may need to be continuously tightened or adjusted in some other way. Measures are therefore partly customized with regard to use (required performance), management and monitoring capacity, the building and the building installation.

With this document, the Dutch trade association for Building Automation aims to provide an explanation of the measures mentioned and a proposal for the working method on how to implement and implement them.

 

3. CONTAMINATION and ROUTES OF TRANSMISSION

 

When choosing measures to prevent contamination, it is important to consider the different measures in order of importance:

Avoid risk: limit large gatherings and large concentrations of people;

Source control: prevent contact with infected persons through quarantine;

Technical measures: for example opening windows and good ventilation;

Administrative measures: adjusted occupancy rate, limit occupancy, administer visitors;

Information provision: inform employees, participants and customers about the current situation.

 

To get a good idea of the measures needed to make workplaces as safe as possible against COVID-19, it is important to know how and through which routes contamination and transmission can take place. Since this will be an ongoing point of research, it is expected that as time progresses, science will develop new insights. These insights must be embedded in devised technical solutions and methodologies.

 

The COVID-19 virus can be primarily transmitted via “droplet contact” by direct coughing. In addition, the virus can remain infectious on a surface for 2 to 3 days, assuming a sufficient concentration of the virus.

Secondary contamination can occur via aerosols. The virus can remain infectious in the air for several hours. The extent to which droplet contact and/or aerosol are responsible for contamination is a source of debate, but it is now clear that it occurs via both. Finally, there is also a possible contamination via fecal-oral transmission.

In general, contamination can occur through direct and indirect contact.

 

Reports and studies indicate that the spread of the Corona virus is the most important factor in contamination and transmission. It is not yet known how big this role is and which circumstances contribute to what extent. The degree of contamination depends, among other things, on:

• Source concentration: how many particles are released or coughed out and how infectious are they;
• How far can these particles spread? This depends on the size of the particles, the speed and ventilation;
• The size of the particles. The larger particles will fall to the ground within a short distance (the well-known 1.5m). The smaller particles can travel further into the room in the form of aerosols and can also be carried along by ventilation. The extent to which this is is still being fully investigated. In addition, the size of the particles is also important with regard to how deeply someone can inhale the particles;
• The duration of exposure;
• The sensitivity of the recipient (natural predisposition, age, condition, health status, etc.);
• Although the exact role of ventilation is still unclear, it is clear that the degree and form of ventilation can influence the spread of the infection. A minimum amount of fresh air is necessary and more fresh air reduces the risk of contamination. How high the minimum should be is not fixed and is also highly dependent on the activity of the person. At the moment we are based on the current building code as a minimum, more is better, but doubling the fresh air quantity, for example, will not immediately lead to a halving of the contamination.

 

Ventilation affects the duration of exposure. As such, ventilation is seen as maintaining oxygen levels and removing spent air (carbon dioxide) and “odors”. In relation to Corona, there is now an additional task of diluting the concentration of micro-organisms in the air and removing them. Because measuring the Corona concentration is not possible, the CO2 concentration is currently often used to determine the degree of renewal and "pollution" of the air.

 

4. RECOMMENDED ACTIONS

 

The measures that can be taken in a building will always be a combination of influencing behavior, adjusting the design and the operation of the installations. It is important to put the user at the center of the measures:

• Make adjustments visible and understandable, so that desired behavior is encouraged and is appropriate in logical and natural behavior.
• Facilitate a working environment in which (building) technology supports the goal of a satisfied user.
• If not yet available, organize a user-friendly and clear way of displaying and monitoring the installations and/or parts thereof.

 

This document focuses in particular on the measures related to the installations. The measures arise from various publications and advice. The following measures are included:

Adjust ventilation quantities

Adjust ventilation operating times

Set continuous ventilation mode

Opening windows

Ventilation and use of space

Toilet ventilation

Sanitary hygiene

Prevent recirculation (central)

Check heat recovery equipment

Fan coil units and ceiling induction units, (recirculation locally)

Heating, cooling and possible humidification setpoints

Cleaning channels

What to do with air filtration?

Indoor air quality monitoring and other GBS data

Smarter use of the available data in the Building Management System and Apps

Substantiated by scientific research, these measures contribute to a greater or lesser extent to preventing the spread of viruses within buildings. It is also important to check the current situation. The design requirements that served in the creation of the building and installations serve as a starting point for determining the technical solutions and methodologies to be implemented, as well as the degree of feasibility thereof.

 

Some measures can be introduced immediately without much effort and others require a more rigorous approach. It is therefore important to consider the required effort and effect.

 

It goes without saying that measures taken may require renewed commissioning, commissioning and/or standardized validation. Measures can cause changes in installations regarding performance and consumption. These must be recognised, accepted and recorded prior to the adjustments.

Likewise, adjustments made can lead to a changed way of dealing with the installations. The receiving management organization must be instructed and/or trained for this purpose.

 

When making adjustments to the installations, it is advisable to also look at the extent to which these adjustments fit in with making the installation more sustainable.

 

A good example of this is when adjusting a fan in an air handling unit to provide more air at a higher desired pressure for better filtering. In that case, it is worthwhile to look at a complete replacement of the electric motor/fan combination with a high-efficiency electric motor or a DC motor with built-in speed control. The additional investment is often recouped within a few years through lower energy consumption.

 

 

5. DEFINITIONS

 

Before discussing the content of how the recommended measures can be implemented, the terms and concepts used must be described clearly and in terms that are understandable to everyone.

 

Most advice has been drawn up by experts and contains (scientific and technical) concepts that are little or not understood by most people. This leads to misunderstanding and lack of acceptance. A clear description of the terms and concepts used contributes to clarity about a subject that is complex for most people and understanding of the need to take measures.

 

 Glossary:

Climate installation	Mechanical installation that provides for maintaining the climate conditions in a building
Ventilation	Supplying and removing air from a building/room in order to supply sufficient oxygen (fresh air) and to remove waste and polluted air (CO2 and "odors"), with the aim of refreshing the air in the room. Additional in relation to the current COVID-19 situation: Ventilation is also used to dilute and remove the infectious air.
Ventilation amount	The amount of fresh air supplied to a room per person or per m². The Building Decree (Article 3.34) specifies the minimum quantities to be adhered to, depending on function and occupancy rate. The definition used by the Building Decree is the purpose of ventilation as described above. Whether this is sufficient to fulfill the additional task of dilution and removal of infectious air is currently unclear; additional research is still being conducted.
Ventilation vs circulation rate	Ventilation rate (VV) is the amount of fresh air supplied to a room per hour in relation to the volume of the room. A ventilation rate of 4 means that the room is completely refreshed 4 times per hour. Circulation rate (CV) is the amount of air (recirculation and fresh air) supplied to a room per hour in relation to the volume of the room. A circulation rate of 4 means that the room is completely flushed with air 4 times per hour.
Fresh air	Is air that is drawn directly from outside
Conditioned air	Treating the fresh air whereby it is filtered, heated, cooled, humidified or dehumidified as required to achieve the desired condition.
Recirculation	Recirculation is the reuse of return or exhaust air which is mixed with the (fresh) air to be supplied. A distinction is made in the method of recirculation: 1) Central recirculation. This takes place in a central air handling unit where air for a building or building part is treated and part of the return air is reused through recirculation. 2) Recirculation between different rooms Within a building, a central system returns air from one room to another room via air ducts. This is similar to 1) 3) Recirculation within one room The air is extracted from the room by a device or system and (partly) returned to this room
Swing fan	Local fan in the room. The air flow provides cooling through evaporation of sweat and faster removal of body heat
Indoor air quality	The quality of indoor air is determined by the concentration of pollutants in it. From an installation technical point of view, this mainly includes chemical contaminants (CO, CO₂, dust) and biological contaminants (Moulds and allergens). A frequently used measure for indoor air quality in user spaces is the CO₂ content. Because the production of CO₂ runs parallel to the production of fragrances by our body, CO₂ is often seen as a derived value of the entire pollution of the air. A value of 350 to 450 ppm corresponds to the outdoor air in the Netherlands. From a value of 800ppm the air is experienced as stale/less pleasant. A value of 1000 – 1200 ppm indicates that ventilation (of fresh air) is insufficient. The MAC value (Maximum Acceptable Concentration) of CO₂ is 5000ppm
Occupancy rate	The occupancy rate is a measure of the m² of usable area per person. The Building Decree uses 5 classes for this (see Article 1.1_6)
Air handling unit	Central facility that supplies a building with conditioned air via central fans. Depending on the application, it provides filtering, heating, cooling and humidification or dehumidification of the ventilation air. An air handling unit is a form of mechanical ventilation
Heat recovery	A facility that is capable of extracting heat from the air to be extracted and transferring it to the ventilation air to be supplied. In addition to heat recovery, some systems can also recover moisture from the exhaust air. Various forms of heat recovery are possible. The most common systems are: 1) Recirculation/Mixed air systems. A certain percentage of the return air is mixed with the fresh outside air and supplied to the building; 2) Twin coil system. This system includes a coil in both the return air and the outside air supply. These batteries are connected to each other by a water system with which the recovered heat from the warm exhaust air can be supplied to the cold outside air. There is no physical exchange of air with this system; 3) Heat wheel. This is a system in which an element rotates between the supply and return channels. This element can absorb the heat from the exhaust air and transfer it to the supply air. Depending on the material of the rotating element, a heat wheel can also exchange moisture. With a heat wheel, there is always a certain possibility of "leakage" from return air to the supply. This depends on the construction, the installation in the air handling unit and the maintenance status; 4) Cross flow exchanger. This is an element in which the supply and exhaust air flow past each other without physical contact. The heat is exchanged because both air flows flow close to each other, separated by a thin ribbed metal plate. Depending on the construction, a cross-flow exchanger may also have limited leakage from the discharge to the supply.
Filters	Filters are used to purify the ventilation air from pollution. The standard air filters used in air treatment systems are capable of capturing particulate matter up to a size of approximately 0.3 micrometers. A commonly used type of filter F7 has an efficiency of approximately 50% for particles of 0.3 -1 µm. In situations where a higher filter effect is desired, an F9 filter is used. This has an efficiency of 85%. Both are therefore unsuitable for completely filtering virus-contaminated air. The filter names have now changed. In the new name, the filters are classified according to the particles they capture and how many of those particles they capture. As a result, the new name can no longer be linked 1 to 1 to the old methodology. (the old methodology included 9 classes, the new 49 classes). It goes too far to discuss this here, see the associated standard ISO16890
HEPA filter	HEPA stands for High Efficient Particulate Air. This filter retains up to 99.99% of all dust particles of 0.3 µm. These filters are mainly used in operating rooms and are able to capture a large proportion of virus-contaminated particles from the air. Note: Virus particles themselves are much smaller, but they cannot float freely in the air. They will always attach themselves to dust particles or (small) water droplets.
UV-C air	UV stands for Ultra Violet light, C stands for the type of UV light. C is an ultraviolet radiation with a wavelength between 100 and 280 nm (short-wave radiation). This light has a sterilizing effect on micro-organisms. Thymine bridges are formed in the DNA using UV light, which prevent the DNA from multiplying. This prevents a micro-organism (fungus, bacteria or virus) from multiplying and an infection is prevented.
Air distribution in the room	The air distribution in the room is mainly related to the supply of ventilation air. An even distribution of fresh air for the users is desirable. The distribution mainly depends on the type of grille used, the location of the grille and ventilation principle
Operating hours	The operating time is the time that an installation is switched on. The installation is often switched on 1 or 2 hours earlier than the times of use to "warm up" the building or to flush it with fresh air, so that when the users enter, it is already pleasant in the building.
Usage times	The usage time is the time that the users are present in the building. Normally the usage time is less than the operating time of the installation.
Measuring and control installation	An automatic control system for independently controlling and regulating the technical installations in a building. The control system will mainly take care of the following functions: § regulate, control and optimize technical installations § regulating various energy flows § maintaining comfort conditions § time-dependent switching of various installations § securing and monitoring installation parts § reporting malfunctions, temperature, moisture and other quality under- and overshoots.
Building Management System (GBS)	A building management system is an overarching system that ensures that the processes in a building run optimally and work together. In addition to climate installations, these processes also include other systems such as lighting, fire alarm and evacuation systems. A BMS mainly has the following functions: § Operation of installations § Monitoring of installations § Recording trend registrations, alarm logs and installation data such as operating hours § Automatically allow different installations to work together in the event of a disaster § Signaling and recording actions to be taken in the event of malfunctions (alarm log and operation logging) The building management system should (preferably) have clear, unambiguous and user-friendly monitoring and display, so that its use is inviting and simple in nature.
Setpoints	The desired value that the variable to be controlled must comply with. For example room temperature etc.
Sensor	Measuring instrument with which the instantaneous value of a quantity is determined. The values are used for the control of the control system, but they can also be used for monitoring and analysis by storing the measured value on the BMS. Traditionally, the sensors are connected by wire to the measuring and control installation. A recent development is that multiple sensors (temperature, relative humidity, presence, etc.) are combined in one device, with communication taking place via fieldbus, Ethernet or wireless. These combination sensors are often used for monitoring in additional applications.
Mechanical ventilation	Ventilating a building or room by using mechanically driven fans that supply and/or extract air from the room.
Natural ventilation	Ventilation is provided by untreated outside air. This air can be supplied to the room via grilles above the windows (Dauerluftung) or via openable windows. This ventilation is “initiated” by the natural draft in a building or limited extraction from, for example, the toilets.
Hybrid ventilation	This is a form of natural ventilation supported by mechanical extraction. Fresh outside air is supplied to the room via grilles above the windows. This is done by the negative pressure of the mechanical exhaust fan that has been specially installed for this purpose.
Venting / Purging	This is a form of natural ventilation in which an air flow is generated by opening windows and/or doors opposite each other. (No mechanical ventilation is used.
Balance ventilation	With this form of (mechanical) ventilation, the amount of supplied air and extracted air are matched. If desired, it is possible to set a slight positive pressure (more supply) or a slight negative pressure (more exhaust) for balanced ventilation.
Mixed ventilation (central)	With mixed ventilation, two or more pre-treated air flows are mixed with each other to achieve the correct supply condition of the ventilation air. Mixed ventilation sometimes also refers to a recirculation system. In such a system, fresh outside air is mixed with already used return air. See also Recirculation.
Mixed ventilation (local) / Induction	With local mixed ventilation, also called induction, the supplied fresh air is blown in at a certain speed and will be mixed with the existing room air through induction. The high speed creates effective, rapid mixing of the supply air
Displacement ventilation	With displacement ventilation, the supply air is introduced into the room at a low speed and a sub-temperature of 2 to 3K. This creates an air layer that pushes the contaminated room air forward towards the extraction point.
March	Draft is an air flow in the room that is experienced as unpleasant by a user. This depends on the relative speed of the air to the user, as well as the circumstance and season. For example, in winter an air flow with a speed > 0.10 m/s can be experienced as annoying, while during a warm summer day a speed of 0.25 m/s is experienced as pleasant. So draft is a very subjective experience. On the other hand, it should be prevented, because it has a very negative effect on the well-being and comfort of the user. In addition to ergonomic reasons, drafts should also be prevented because of the relationship with absenteeism due to illness as a result of drafts.
BaOpt principle	Air systems that are designed according to the BaOpt principle are based on diffuse air mixing. This results in rapid and homogeneous air mixing. The BaOpt system works based on air pressure control based on temperature and CO₂. When using a BaOpt system, it is worth considering the fresh air limiting control settings based on air pressure control and/or CO2.
Fan coil unit/fan convector	A fan convector is a local unit, which is often placed in the ceiling or against the wall. The unit is equipped with a heater and/or cooler block, a fan that can be set to multiple speeds (manual or automatic) and equipped with a simple air filter. A fan convector works standard with recirculation from the same room (see recirculation 3), whereby a connection for fresh air from a central air treatment system is often available.
Induction unit	An induction unit is a local unit, which is often placed in the ceiling or against the wall. The unit is equipped with a heater and/or cooler block. The “drive energy” of an induction unit is the primary fresh air from a central air treatment system. Through induction (negative pressure), the unit sucks in secondary room air and mixes it, heats it, cools it and then blows the air back into the room. An induction unit therefore also has a form of local recirculation (see Recirculation 3).

 

 

 

6. WHAT TO DO?

 

In order to be able to take the measures mentioned in Chapter 4, the current state of affairs and the design principles of the climate installations must be determined. Only then can deviations be identified and the desired adjustments implemented. For this purpose, a quick scan can be made of the building and its installations. A number of important questions arise:

What should at least be included in this quick scan?

Who can carry out this inventory?

When should the quick scan be performed?

How and who determines which measures should be implemented?

 

Quick scan contents:

Using the quick scan, an initial inventory can be made of the measures to be taken. A uniform question leads to more clear reporting and advice. Components that must at least be included in the quick scan:

• Design principles regarding ventilation and occupancy.
• Current occupancy and use in relation to the original design (is the building/space still being used for what it was once designed for?).
• Design and implementation of climate installation and ventilation system centrally and locally.
• Inventory of building management system and measuring and control installation
  • Implementation of climate control system and the presence of a central BMS
  • Climate installation settings (including: set points and operating and usage times)
  • Presence of sensors, location, type of implementation and accuracy of measurement
• What is the desired situation?

 

Who can carry out this inventory?

For this note we limit ourselves to the technical installations and matters related to them.

The inventory can be carried out by:

• Our own maintenance and management service;
• The maintenance party;
• The installation advisor;
• Combination of the parties mentioned

 

The following can serve as a basis for the inventory:

• The program of requirements
• The cutlery
• The revision modest
• The building management system
• The available logs
• The knowledge of maintenance and management services

 

Based on the inventory, an action plan can be drawn up in which the measures can be recorded in order of importance and feasibility.

It is important to have the plan tested by an expert with regard to the COVID measures.

 

In a second period, a more detailed investigation can take place into the actual operation of the various systems. This includes carrying out control measurements with regard to ventilation quantities and monitoring the climate installation.

 

When to perform a quick scan?

In many cases, fresh air and ventilation can still be achieved by opening windows and doors. However, in autumn and winter this is not an attractive option. A properly functioning ventilation system may then be necessary.

During that period, this implies that quick scans must be carried out as quickly as possible. Appropriate speed combined with good soundness is also recommended from the point of view of providing clarity to users and organizations involved.

 

 

What measures need to be implemented?

It is important to recognize that the advice comes from multiple parties, which do not always agree with each other and that the scientific substantiation is sometimes not yet available or incomplete. The question still remains: who are the experts? The government follows the advice of the RIVM. The RIVM has its own specialists and is in turn provided with information from external advisors. In addition, the WHO and various interest parties are also active in this.

 

The Corona Expert Panel has been established in the Netherlands, a collaboration between TNO, TU/e, VCCN and RoyalHaskoningDHV, (expert.panel.corona@TNO.nl). This was primarily intended for healthcare, but the panel is now also focusing more on other components. Questions can be asked at the Corona Expert Panel. They also publish a FAQ overview, which is available via the website. TVVL has published an overview of measures on their website and shows various studies here. Advice is also available via Masterplanventilation.nl and Binnenklimaattechniek.nl. A COVID 19 Guidance document has been drawn up by the REHVA.

 

The measures now mentioned in Chapter 4 are based on the advice of the above authorities or a consensus that the measures mentioned will have an effect, under the guise of “better safe than sorry”.

 

Once the quick scan has been made, the building and the (climate) installations have been inventoried and a number of conclusions can be drawn based on this regarding the need for measures to be taken.

 

On this basis, an Action Plan (PvA) must be drawn up. This PvA must include at least:

• Conclusions from the quick scan
• Proposal for measures to be taken and intended result
• Method of implementing these measures
• Indication of measures that are NOT proposed with reasons and consequences
• Budget price for measures to be taken
• Priority list of measures to be taken
• Intended implementation timeline

 

The speed with which they can be introduced, the degree of impact of the measure on the organization and of course the costs influence the choice of measures. The advice is to implement the so-called quick wins immediately. A guideline for this is given in Chapter 8. In addition to consequences, a chapter should be devoted to the method of testing the measures after implementation has taken place. This should address the commissioning method, commissioning and possible validation.

 

What should also not be lost sight of is indoor climate safety in relation to the comfort and well-being of the user. After all, the aim is to make these go together. The measures that lead to reduced comfort will lead to complaints from users. It is important to take the user's well-being into account when implementing the measures and to make the adjustments visible and understandable.

 

 

7. WHEN IS A BUILDING SAFE?

 

Building owners and users need guidance to determine whether their building is safe to use. However, a “safe for use” stamp or a quality mark is missing and cannot be given. We cannot make a building “flu-proof” for any infection. There is always a chance of contamination.

 

The question is also what to do if a number of the desired measures cannot or cannot be fully realized with the current technical installations? There is a chance that this situation will occur. Does this make a building not safe?

The latter cannot be said like this and is very situation dependent. This document does not aim to make that assessment for buildings. The purpose of this document is to provide guidance on this point to building owners and users, to describe to them the possible measures that provide support and substantiation for decisions regarding the use of the buildings.

 

It is also important to determine whether the measures taken have been properly implemented and whether they have or will have the intended effect. This means that depending on the measures taken, an additional check must take place. The advice is to make this inspection part of the PvA and a supplementary commissioning plan.

 

8. FROM THEORY TO PRACTICE PER MEASURE

 

Below is a more detailed description of the measures mentioned with at least the following information:

• Brief description of the measure and what its (positive) consequences are
• How to achieve this and the advice for adjustment
• Then how to check

 

All measures must be put into operation in an orderly manner, checked for proper functioning and, where necessary, extensively functionally tested. Changes in design and principles must be properly recorded in logbooks and revision documents. And users must be properly instructed.

 

8.1. Adjust ventilation quantities

 

The basis of this measure is to ensure as much as possible that there is sufficient fresh air to dilute the infectious air and remove it. This is achieved by increasing the amount of fresh air for the users. The key question then is: what is sufficient fresh air? In addition, the efficiency of ventilation is just as important. There is no point in supplying large quantities of air to a room if the flushing of this room is not good, for example due to poor grille distribution.

 

RIVM prescribes that a minimum building code for ventilation must be adhered to. There is currently a lot of discussion about this (particularly in schools). Building Decree requirements for ventilation are mainly drawn up to maintain sufficient oxygen in the room and limit CO₂ concentration, sufficient fresh air to provide a somewhat fresh indoor climate, removal of moisture to prevent mold formation on the walls, etc. The building decree requirements are not specifically designed to prevent virus contamination via air in buildings.

For example, for an office application, the Building Decree indicates: 6.5 dm3/s pp, which is 23.4 m3/h per person.

It is striking that within the building decree there is little variation in the air volume based on activity level or metabolism. The same requirements apply to space with a sports function as to an office and a daycare center. In practice, additional requirements are often formulated to achieve a higher quality indoor environment. The requirements described in the building decree are taken as the minimum basic value. There are various guidelines that all work with a number of classes/ventilation levels where one can make a trade-off between costs, comfort and energy use. And now in relation to COVID19 to the renewal rate of the air.

 

For example, the practical guideline NPR-CR-1975 defines 3 quality classes ABC, this has been adopted in PVE healthy offices and ISSO practice book healthy buildings Cahier T1. The PVE fresh schools also defines 3 ambition levels for schools. And the latest standard NEN-EN 16798-1:2019 even defines 4 classes.

 

Class	NPR-CR-1752	PVE healthy buildings	PVE fresh Schools	NEN-EN 16798-1
	60 m3/h pp	60 m3/h pp	43.2 m3/h pp	(kl I) 72 m3/h pp
	40 m3/h pp	40 m3/h pp	30.6 m3/h pp	(kl II) 50.4 m3/h pp
	30 m3/h pp	25 m3/h pp	21.6 m3/h pp	(kl III) 28.8 m3/h pp
				(kl IV) 19.8 m3/h pp

Table 1: compare ventilation quantities

 

It is currently unknown what a safe minimum ventilation rate (VV) should be. A lot of research is being done into this. But with the help of ventilation, the virus concentration in a room can be reduced by supplying fresh air, clean air and removing the polluted air. However, it is not so much the amount of ventilation air that is important, but rather the effectiveness of the ventilation at room level. Is a room sufficiently flushed and does the fresh air also reach the people present?

 

It is generally accepted that for an average indoor climate comfort, at least class B must be met, regardless of the chosen guideline. Offices with a climate class C are generally experienced as less pleasant and class A provides a clear increase in comfort. So where possible, it is recommended to maintain at least climate class B or to increase the ventilation flow.

 

The amount of ventilation air is based on:

• Available capacity of central air treatment;
• Ventilation effectiveness;
• Implementation of central air treatment, recirculation and/or CO₂ control (central);
• Building occupancy;
• Available budget.

 

How to realize?

The quick scan determines the current available air volume and occupancy. The ventilation amount per person can be calculated from this. This must be reflected in the desired and future occupancy. From this it can then be determined what the capacity of the existing installation is in relation to the desired capacity. In addition, it is important to recognize how the ventilation system works (e.g. recirculation, heat recovery? etc) and how it is controlled (e.g. fixed flow, speed-controlled, or CO₂?...)

 

Central air treatment capacity is sufficient based on the quick scan.

• If the quick scan shows that the air volumes on paper are sufficient, a check of the correct operation and adjustment will suffice.
• Perform a visual check of the central air handling systems. Is the unit clean and what is the status of the air filters?;
• Carry out a functional check of the central air handling systems. Have air measurements carried out on the AHUs to check whether the design values are being achieved. A deviation of maximum 10% is acceptable;
• Have the air volumes measured in a number of main ducts and take a few random samples in the rooms. If more than 30% appears to deviate from the measurements by more than 10%, have everything checked;
• As an alternative to air measurements, the CO₂ content can also be measured in the room (during use). The CO₂ level does not directly say anything about the risk of contamination, but it does indicate to what extent the ventilation of a room is sufficient in relation to the prevailing occupancy. A low CO₂ concentration does not mean that the risk of contamination is low, but a high CO₂ level does give a warning that ventilation is insufficient. As an example, a maximum CO₂ content of 900 ppm can be used. If it is higher, it is recommended to ventilate more or reduce occupancy.
  
  

Increase central air treatment capacity.

• Investigate whether the air treatment flow rate can be increased;
• Are the fans equipped with frequency control? ;
• Check heater and cooler capacity at design conditions, outdoor conditions and increased flow rate;
• Checking system adjustment at increased flow rate;
• Increasing the flow rate can result in higher energy consumption.

 

 

Central air conditioning has a recirculation facility.

• If the air treatment is carried out with central recirculation, it is especially important whether the fresh air proportion is sufficient. Operating with 100% outside air is preferable for air renewal, but is not always necessary. Also from the point of view of healthy buildings, central recirculation is no longer used nowadays, but existing buildings can still have such an installation. Recirculation is often a reason for reducing heating and cooling capacity. In such situations, operating 100% on outside air is more likely to lead to a less well-functioning ventilation system. Recirculation can actually increase ventilation effectiveness if 100% with outside air is not feasible. But from the point of view of air quality, the advice is to maximize the amount of fresh air and thus limit recirculation as much as possible within the comfort requirements.
• Check heater and cooler capacity at design conditions, outdoor conditions and 100% outdoor air.

Increase the outside air proportion if there is sufficient capacity;

• Adjust the central air treatment control setting, so that the control of the mixed air control is adjusted to a 100% outdoor air or a minimum required recirculation part;
• Closing recirculation can result in higher energy consumption.
  
  

 

 

Central air treatment has a speed control based on CO₂.
If the air treatment is equipped with a speed control based on CO₂, whereby the air quantity is reduced at a lower CO₂ content, then this control must be turned off, or at least set in such a way that the fresh air quantity never falls below the specified requirements.
Depending on the location of the CO₂ sensor, the set point of the control can optionally be adjusted in such a way that the control no longer intervenes in practice. For example, by setting a CO₂ sensor in the room to 350 ppm or lower. This value corresponds to or is lower than the outside condition, so that the control provides maximum fresh air.

Capacity of the central air treatment does not meet the current or desired occupancy.

Reduce the occupancy of a building. Because the available ventilation air is required for fewer people, the fresh air flow rate per person increases. Please note that people are not concentrated in one location, but are spread throughout the building. Take the 1.5 meter rule into account and preferably increase the distance between people (if possible).
This can also be an interim solution if user requirements remain the same.

If reducing the occupancy is not possible, it is advisable to conduct a study into the possibilities of increasing the ventilation capacity.

What to do with a building or room with limited or only natural ventilation?

• It is preferable not to use this space;
• Instruct users to always open the windows, at least a crack;
• Preferably try to achieve some form of cross ventilation by opening windows or door(s) against each other. However, try to avoid people sitting in the draft.
• It should be realized that flushing in itself is not an alternative, ventilation must always be in order. It is therefore advisable not to use spaces that cannot be sufficiently ventilated.
• If such areas are used:
  • Take regular breaks during which the room is heavily ventilated by opening the windows completely.
  • Install a CO₂ sensor in this room with an indication, via display or "traffic light" (green = CO₂ level sufficiently low, orange (600 ppm) = pay attention to more ventilation, red (>900 ppm) = unsafe, leave the room and flush extra. NOTE: the CO₂ sensor is not a measure of the risk of infection, but only an indicator of the ventilation capacity and efficiency.
  • If the CO₂ concentration is continuously too high, reduce the occupancy rate.

 

8.2. Adjust ventilation operating times

 

By increasing the operating times of the ventilation compared to the times of use, better flushing of the building is achieved. This pre- and post-ventilation is also done in many installations from a comfort point of view, starting earlier to ensure the building is at the right temperature before the users arrive, and at the end of the day to "turn off" the heat. If these functions are already present, additional ventilation is often not necessary. Initially it was indicated to ventilate for 24 hours, but this has been adjusted; limited pre- and post-ventilation is also sufficient.

 

How to realize?

For example, by allowing the ventilation to function at the nominal flow rate 2 hours before the start of the usage time and 2 hours longer, a better flushing is achieved and after the usage time the contaminated air is removed. The exact ventilation time can be determined based on the ventilation rate of the rooms.

• Adjustment can often be made by adjusting the clock programs in the measuring and control installation;
• If you have multiple clock programs, please note that they are all adjusted;
• Also check whether heat and cold generation are switched on;
• Increasing operating time will result in higher energy consumption, so it is recommended to combine this function with a self-learning heating function to prevent unnecessary ventilation.

 

8.3. Set continuous ventilation mode

 

In addition to increasing the operating time, it is also recommended to continue running the ventilation outside operating hours if possible. However, it is not necessary to operate the installation for 24 hours. With an efficient system, the rooms are sufficiently flushed after a few hours to sufficiently remove the polluted air. It is sufficient to provide additional ventilation to the building for a limited period of time before and after use, see 8.2.

If you choose to run the installation at night, it is advisable to run the ventilation at a lower speed outside operating hours.

8.4. Opening windows

 

In buildings without mechanical ventilation, it is advisable to actively use the windows that can be opened. Much more than one would normally do. Even if this leads to local thermal discomfort. Opening windows is the only option to ventilate a room. However, one must be fully aware that from the point of view of the risk of contamination it is very undesirable to use spaces without ventilation.

How to realize?

The windows should be opened as much as possible, even before using the room. Also try opening several windows opposite each other to increase flushing.

An attempt can be made to open windows/doors by someone prior to operating time. This also applies to closing it. However, the aspect of safety and unwanted access to the building must be taken into account.
In addition, one should be aware that drafts will often lead to discomfort and can also lead to transmission from person to person when one is in “each other's airflow”.
See also 8.6 point 6.

 

8.5. Ventilation and use of space

 

There are a number of points to consider when using ventilation to prevent spread and contamination as much as possible:

• Prevent a room from being used by more people than it was designed for;
• Prevent people from sitting in someone else's airflow;
• Also prevent air flows through the building from one zone/open plan office to another;
• Ensure correct air direction, as much as possible from the room directly outside and not via a corridor or other room;
• No long meetings with many people in a small room with limited ventilation.

 

How to realize?

• Prevent use by too many people

Clearly indicate at the entrance to the room how many people may use this room. Also record this in internal protocols;

• Prevent airflow to another person
  Check how the air is blown into the room and if this gives a large air flow from one to the other, adjust the seating positions (or adjust the system or the method of blowing in (blow pattern)). Please note that adjusting the blowing pattern can lead to draft complaints;
• Preventing air flow between 2 rooms/zones
  Check air flows, for example with a test strip. Close doors between rooms (if present) and place screens between zones to separate them.
  Adjust intake patterns of grilles where necessary.
• Check air flows, for example with a test strip.
  Check the design of the air installation and determine to what extent adjustment is possible. PLEASE NOTE: In the absence of mechanical ventilation, air flow can vary due to weather changes.
• Areas with insufficient ventilation
  Take out of use areas with insufficient ventilation or limit the number of people.
  PLEASE NOTE: Draining rooms after a meeting is not an alternative. There must be enough continuously are also ventilated during the meetings, so that the particles are continuously diluted and removed;

 

 

 

8.6. Toilet ventilation

 

It is important that the ventilation is such that the sanitary areas are at negative pressure compared to the surrounding areas. The extraction of the toilets can be in operation 24/7. If adequate cleaning of the toilets takes place within operating hours, the extraction ventilation can be switched on during the (extended) operating times according to 8.2.

 

Assuming properly functioning ventilation and sufficient cleaning, the risk of contamination via visits to a toilet is currently estimated to be very low and no additional measures need to be taken. The advice is to increase the cleaning frequency of the toilets themselves.

8.7. Sanitary hygiene 

 

A number of management protocols are necessary for sanitary facilities:

• Prevent siphons from drying out during prolonged standstill/non-use by periodically flushing or pouring a little olive oil or the like into the siphon.
• Prevent legionella contamination during prolonged standstill/non-use.
  If a building has been out of use for a long time due to working from home/limited occupancy, it is recommended to carry out a risk analysis with regard to legionella risks and take the necessary measures.

Also consider floor drains and siphons in technical rooms and work cupboards, the same measures apply.

8.8. Prevent recirculation (central)

 

If the air treatment is equipped with recirculation, take a closer look at this facility and investigate the possibility of limiting or turning it off and only running with 100% outside air, see also 8.1. This also applies to recirculation of air between different rooms, where the air is brought from one room to another room. For the latter, ventilation efficiency is more important than limiting recirculation.

 

How to realize?

See also point 8.1. part 3

• Adjust the central air treatment control setting so that the mixed air control is undone.
• Physically secure the mixed air valve to ensure that it remains closed.
• Check heater and cooler capacity at design conditions, outdoor conditions and 100% outdoor air.
• Pay attention to ventilation effectiveness, this must be guaranteed when adjusting the mixed air settings.

 

8.9. Check heat recovery equipment

 

Various heat recovery systems are possible for air treatment. The systems in place are known from the quick scan. However, depending on the implementation, there is a risk of contamination or transmission. Such systems must be adjusted or switched off. The following systems are (usually) applied:

• Recirculation/mixed air
• Twin-coil system
• Heat wheel
• Cross flow exchanger

 

 

How to realize?

Check on applied heat recovery system

• Recirculation/mixed air
  With this system there is a risk of contamination from contaminated return air.
  – Preferably turn off recirculation. This can be done by adjusting the setting of the control.
  – Physically secure the mixed air valve to ensure that it remains closed.

    – Check heater and cooler capacity at design conditions, outdoor conditions and 100% outdoor air.

    – Pay attention to ventilation effectiveness, this must be guaranteed when adjusting the mixed air settings.

See also point 8.1. and 8.8

• Twin-coil system
  With a twin coil system there is no risk of contamination. Such a system can simply remain in operation.
  
  
• Heat wheel
  A heat wheel has a small air leakage from discharge to supply. The most important leakage from a heat wheel is from the discharge side to the fresh supply air at the location of the physical transition 

between supply and discharge. If the exhaust fan, viewed upstream, is placed behind the wheel, this leakage is small due to the negative pressure. But a (small) leak remains present. 

Modern heat wheels are usually equipped with a flushing zone, so that during the transition from exhaust to supply, any residual air in the heat-exchanging package is discharged to the exhaust. 

This prevents contamination from the exhausted air from entering the fresh supplied air via the rotation of the heat wheel, but small leakage also occurs with these systems. 
If a heat wheel is properly constructed, installed and maintained, the leakage percentage is very low (1-2%). This type of heat wheel can continue to function. It is advisable to have the maintenance of the heat wheel carried out in accordance with the manufacturer's guidelines.

If a heat wheel is installed in such a way that there is a higher discharge pressure on the exhaust side, there will be a significant leakage that can amount to more than 5%. Then there is a transfer from the exhaust air to the supply air. This means there is a possibility of transferring contamination due to the pressure hierarchy and leakage loss. In normal (office) situations, the chance of transmission of infection is small, assuming that no COVID-suspected persons are present.

– the advice is to check the heat wheel for correct construction, installation, leakage and maintenance. If this is satisfactory, the heat wheel can remain in operation.

– If it is not satisfactory and in particular the pressure hierarchy is not good, additional research is required to determine the extent to which the leakage occurs and what the situation in the building is in relation to the presence of COVID-infected people.

– PLEASE NOTE: when the heat wheel is stopped, it will become contaminated on one side, which means that it must first be properly cleaned before the heat wheel is started again.

– Checking the heater and cooler capacity at design conditions, outdoor conditions and 100% outdoor air is also necessary.

 

• Cross flow exchanger

A cross-flow exchanger has minimal air leakage. A cross-flow heat exchanger with a pressure regime in which the pressure at the location of the 

cross-flow exchanger is higher than the pressure of the discharged air at the location 

heat exchanger results in a low degree of air transfer, in the range of 2%. This is acceptable and the cross-flow exchanger can continue to operate.
If the leakage is greater, it is recommended to try to remedy this. If this is not possible, take the cross-flow exchanger out of use by continuously opening the by-pass valve.

 

8.10. Fan coil units and ceiling induction units, (recirculation locally)

 

Fan coil units and induction units are local systems that heat and/or cool the spaces. They are equipped with air recirculation in one common room. Recirculation of room air can contribute to the spread of the virus. However, without the recirculation units, the virus will also be able to spread through the room, but with recirculation it may go a bit faster. In contrast, the local concentration in the vicinity of the source will decrease more quickly due to such a system. But if one considers that this concerns a space in which one is present for a longer period of time, this contribution is minimal. It is important that there is sufficient renewal of the room air through the supply of fresh air. The fresh air ensures dilution and the removal of polluted room air. Because these units also ensure good air distribution and ventilation efficiency, they should certainly not be turned off.

 

It is important that these recirculation units can only be used if sufficient fresh air is supplied to the room. The question is what is enough? See 8.1 adjusting ventilation quantities. It is currently unknown what a safe minimum ventilation rate should be, but research is being conducted into this. But adhering to the values from chapter 8.1 is considered sufficient for the time being.

 

How to realize?

The quick scan shows which systems are present, how they are dimensioned and what capacities they have in relation to the space and occupancy.

When using Fancoil units:

• How much fresh air is supplied?
• Can this be enlarged?
• Is the fresh air connected directly to the fan coil unit or to separate grilles? With a direct connection, when the fresh air portion increases, the unit must also be able to deliver more capacity, depending on the primary air temperature;
• During operating time, the unit's fan must always be in operation and must not be switched off.

 

When using Induction units:

• What is the capacity of the units, in particular the air quantities?
• How much fresh air is supplied? When increasing the air volume, the nozzles of the unit often also have to be adjusted. Coordination with the supplier is necessary to determine what is possible. Is this possible without replacing the unit?
• During operating time, the unit must always be in operation and must not be switched off.

 

8.11. Heating, Cooling and possible humidification setpoints

 

The average settings that apply to climate installations are approximately 21 to 24°C for temperature and 40 to 60% for relative humidity (with controlled humidity). The question is whether adjusting these settings can contribute to limiting the spread of the COVID-19 virus.

 

Little is known about the relationship between temperature and relative humidity and the viability of the COVID-19 virus. Limited studies have shown that only extreme conditions (>30°C and >80%RV) influence the lifespan of the virus. Lower relative humidity causes small aerosol particles to decrease in diameter and spread more quickly in the room, which reduces the concentration of these particles and allows them to be removed more quickly.

Dry air (lower than 20%RV) affects the functioning of the mucous membranes of people who are susceptible to this. Irritated mucous membranes are less able to perform their "vacuum suction" function and therefore a very dry environment can influence the susceptibility of people, but not the spread of the virus. Under normal conditions, the relative humidity in a room without humidification will be between 30 and 70%. This means that the conditions do not require additional humidification or dehumidification of the air. The prevailing room temperatures of 21 to 24°C are also no reason to adjust.

 

It is recommended not to make any adjustments to the settings of the climate installations.

If a hygroscopic heat wheel is present and has been stopped, it must be taken into account that due to the lack of moisture recovery, the humidity may deviate from the regular values.

 

8.12. Cleaning channels

 

Periodic cleaning of air ducts is generally useful (and if carried out properly), but it has no impact on reducing the transmission of the coronavirus. The basic principle here is that there is no recirculation in the central air treatment system. In addition, the COVID-19 virus is very small, which means that deposition in channels will be minimal. If the virus attaches to a larger particle, deposition may occur, but it will no longer be viable within a few days.

 

8.13. What to do with air filters

 

• Central outdoor air systems:

The air filters in a central air handling unit that draw in outside air are not exposed to the COVID-19 virus. These therefore do not need to be replaced. Using the normal replacement frequency is sufficient. The return filters of a central air handling unit generally protect a heat recovery system against contamination. Assuming that no recirculation is used, the filters do not need to be replaced here either.
When replacing the filter, it is advisable to use sufficient PPE (gloves, respiratory protection, safety goggles (preferably a face mask)) and to put the old filter in a sealable bag.

PLEASE NOTE: if a system has been standing still for a long time due to the lock-down, filters can become dirty because stagnant air can cause mold and bacteria growth. The advice is to replace the filters.

 

• Decentralized filters

Decentralized filters in, for example, fan coil units or induction units do not need to be replaced. Use the normal replacement frequency.

 

• Local filter/cleaning by UV-C, ionization, etc.

Studies show that the use of UV-C radiation can inactivate viruses and reduce the survival rate. This also applies to ionization of air and air purification with ozone. It must be realized that such studies have often been done in a controlled (laboratory) environment and that the systems have not yet been sufficiently tested in practice for the COVID virus.

The setup and implementation of such a unit are of great importance. There is no point in placing a unit in the corner of the room. When using UV-C units, it must be proportional in relation to maintaining sufficient distance, the degree of ventilation, the chance of the presence of contamination or an infected person and the occupancy of the room. Also important with these forms of air purification is the creation of residual products that can pose a risk to health. Consider an excess of ozone, which leads to headaches, dizziness and sore throat. A good control system, correct adjustment and control are essential for the use of these systems. If this is taken into account, there is no obstacle to the use of these filters, but one must realize that the effectiveness is highly dependent on the capacity of the filter in relation to the room in which it is used.

 

Local air purifiers are usually suitable for cleaning a limited space. When using a local filter system, good recirculation over the units is important. Extra attention should be paid to the capacity and Clean-Air-Delivery Rate scores of the units. Sufficient flushing of the room must be guaranteed. Ask an independent specialist for further advice before purchasing local air cleaners. Application of HEPA filters in, for example, a recirculation unit instead of the above-mentioned filter techniques is expected to be at least as efficient.

PLEASE NOTE: local air purifiers are not a replacement for ventilation systems but additional! The described methods such as UV-C cleaning, ionization and HEPA filters can also be applied within existing duct systems and air treatment. However, this does require the necessary adjustments with regard to installation and control. When using HEPA filters, a significant increase in the required pressure must be taken into account.

 

How to realize?

For local filter units:

• Determine the capacity of the unit in relation to the space (realize that the capacity in relation to the space is often limited. For full utilization, a flush of at least 2 to 5x the space volume is required);
• Determine a correct arrangement in relation to occupancy and use of the space;
• Choose a device that is equipped with sufficiently accurate control;
• Check whether sufficient (electrical) power is available.

 

 

For filter units in central air systems:

• Determine the capacity of the unit in relation to the air system (this often leads to a considerable investment);
• Choose a device that is equipped with sufficiently accurate control;
• Check whether sufficient (electrical) power is available;

When using HEPA filters, check whether sufficient pressure is available in the ventilation system.

 

8.14. Indoor air quality monitoring and other GBS data.

 

Monitoring indoor air quality can provide early warning when, for example, there is insufficient ventilation. CO₂ sensors are often used to determine air quality. The CO₂ content in the air is a derived value of the quality of the air. This does not mean that a high concentration of CO₂ in the air also immediately means highly infectious air. This only implies that the air renewal is less good. With a view to the dilution and removal of polluted air, a high CO₂ value can therefore have a warning function that ventilation is insufficient.

 

The quick scan revealed whether and which sensors are used in the building. If air quality sensors such as CO₂ and TVOC sensors are connected to the building management system, it will be necessary to determine where these measurements are taken and to what extent they can be translated back to the rooms and their users. If the CO₂ sensors are used to control the speed of the central air treatment, these controls must be (temporarily) out of use, or at least adjusted to more fresh air, by adjusting the set point (see also 8.1. Adjusting ventilation quantities).

 

It is recommended to install a CO₂ sensor with local readout and a traffic light function in all user areas. Users can then see for themselves what the air condition is in the room. They can take their own measures according to a previously issued instruction (open windows, doors or leave the room and flush). For rooms that do not have mechanical ventilation, but only have natural ventilation, the use of local sensors is urgently recommended. (It is better not to use these spaces, or use them as little as possible).

 

There are currently various (web-based) solutions for local CO₂ sensors available. This allows the condition to be monitored locally. By monitoring these sensors via the internet or via BMS, one is also able to recognize and anticipate patterns. For example, the increase in CO₂ levels has a direct relationship with occupancy as a result of planned meetings. Daily, weekly and monthly reports can also be printed and recurrences in high concentrations can be identified so that measures can be taken.

 

How to realize?

CO₂ sensors control central air treatment:

• Turn off the CO₂ control so that there is always maximum ventilation;
• Optional: Adjust control setpoint setting. Where a setting at 350 ppm CO₂ leads to maximum ventilation (350-450 ppm CO2, this corresponds to the outside air quality, so the unit will ventilate maximum to achieve this). It is also possible to set the set point higher, taking into account the minimum ventilation quantities required;
• Include the sensors in a trend registration on the BMS and monitor the occurring values. If these are still too high (higher than 900ppm with full ventilation) then the operation of the ventilation system must be checked and a check on the occupancy of the building or space (too many people for the available fresh air);
• Investigate the possibility (technically and budgetary) of expanding the number of sensors, possibly in combination with a web-based sensor network (see below).

 

CO₂ sensors locally for signaling:

• Inventory the number of rooms and occupancy (known from the quick scan);
• Make an inventory of the different options for measuring and placing the CO₂
  • local and stand-alone;
  • local and connected to GBS;
  • locally in a web-based sensor network;
  • battery powered – or external power supply…..

The advice is to involve an expert in this. There are numerous parties that offer sensors. With or without a web-based (wireless) network. Such a network solution can often be easily installed, because sensors are battery powered and can communicate wirelessly. As a result of the battery power, there is often no display or traffic light function;

• Determine budget and technical possibilities;
• When using a local CO₂ sensor, preferably also a display with alarm and/or a traffic light function: “traffic light” (green = safe, orange (600 ppm) = pay attention to more ventilation, red (>900ppm) = unsafe, leave the space and extra flushing;
• Ensure that clear instructions are available for users.
  
  
  • Smarter use of the available data in the GBS and Apps

 

The building management system has a lot of data that is hardly used. During the quick scan, an in-depth overview can be made of the available signals. In addition to temperature, RH and CO₂ measurements, these include limit value reports of filter contamination, operating hours counts, and operating and fault reports of pumps and fans, but also, for example, the presence of people in the room or their number. Based on temperature, CO₂ and presence trends, an image can be formed of the occupancy of the building and this can be controlled in the operational sphere.

By better aligning fault handling and maintenance with the data from the BMS, potentially dangerous situations can be (better) prevented. For example:

• Replacement/checking filters based on limit value notification of filters contaminated instead of time-controlled (1x per/year);
• Flow measurements of air treatment systems, if the set point is not reached, an alarm will sound that there is insufficient ventilation;
• The same applies in the event of system failure, immediately report that there is insufficient ventilation.

 

In short, by making better use of available data within the BMS, a more adequate response to disruptions can be made and potentially dangerous situations in the context of COVID-19 (too little ventilation or poorly functioning systems) can be prevented.

 

In addition, various applications are now available within the built environment (whether or not via the building management system, or through additional APPs on mobile telephony).

 

Examples of this are:

• Space management and reservation of workplaces via GBS or APP.
  This allows an (online) picture to be formed of the availability and occupancy of rooms and workplaces. By setting up a system where users have to reserve their workplace in advance, the occupancy of a building can be controlled.
• Reservation of meeting rooms via GBS or APP.
  This allows an (online) picture to be formed of the availability and occupancy of meeting rooms. By setting up a system where users must reserve meeting rooms in advance, the occupancy of the meeting rooms and the number of people/room can be controlled.
• Heatmaps regarding the presence of the number of people. This can be done inside a building or outside. Via APPs you can see information about where it is (too) busy.
• Based on the count via the access control system, the number of people in the building is known and ventilation can be adjusted accordingly. (Note: this mainly concerns the minimum quantity to be set)
  This can be even more accurate provided that more data is available on the location of the people in the building. (for example through attendance registration in the GBS)
• Crowd monitoring via 3D camera, this system can provide insight into crowds and mutual distance.

 

This entire chapter is aimed at making the theoretical measures practical. We hope this information is useful in your daily practice.