FAQ Ventilation
1. Does the Law of 6 November 2022 impose any obligations concerning ventilation?
Regarding ventilation, there are currently no obligations on the operators and owners of the spaces.
2. Why is ventilation important?
Ventilation is essential for good indoor air quality and thermal comfort. There are many reasons for installing a ventilation system. The first is to provide sufficient fresh air for the metabolism and dilution of contaminants. By extracting air, a ventilation system removes contaminants, unwanted heat and humidity from a room. This reduces the risk of allergies and respiratory irritation. In addition, a ventilation system provides sufficient oxygen for combustion and separates the various elements of an indoor environment to isolate a polluted zone. A smoking area is an example of isolation. Ventilation systems create a pressure difference between rooms to prevent pollutants from entering or leaving.
Insufficient ventilation can lead to discomfort, irritation when performing activities, respiratory failure and even health problems. It is therefore essential that ventilation systems are adapted to the specific needs of the space, and in particular of the people performing any activities, if applicable.
3. What types of ventilation are available?
There are three main types of ventilation: natural, mechanical and mixed.
Natural ventilation is a process that uses differences in temperature, pressure and outdoor air to renew indoor air without the aid of mechanical systems. It is based on physical phenomena such as the movement of air due to heat (hot air rises, cold air sinks) and openings (windows, doors, skylights, vents, ventilation grilles) that allow outdoor air to enter the building and stale air to escape. The effectiveness of natural ventilation depends on the size and orientation of the building's openings.
Mechanical ventilation uses air ducts and fans to circulate air. Mechanical ventilation consists of two separate duct networks: one for supplying air from outside and one for extracting air to the outside. Mechanical ventilation offers maximum flexibility, eliminating contaminants directly at source and maintaining a comfortable thermal environment. As mechanical energy is used to supply and extract air, it is independent of weather conditions. Even if the wind speed outside is low, the ventilation rate in a room is not affected. The capital cost of mechanical ventilation is higher, as two separate duct networks have to be installed, and the energy requirements of fans are higher.
Mixed ventilation is a system that uses both natural and mechanical ventilation strategies. For example, in summer, mechanical ventilation systems are used to remove unwanted heat and provide fresh air to a room to create a comfortable environment, and in mid-season, natural ventilation is used to provide fresh air to dilute airborne contaminants and remove contaminants to maintain indoor air quality. Using mixed ventilation saves even more energy.
4. How can ventilation stop the spread of viruses?
When we breathe, speak, cough or sneeze, we emit a larger or smaller number of water droplets in the air we exhale. If we are infected by viruses or microbes, these droplets are loaded with them.
The largest drops fall very quickly onto surfaces and the ground, but can contaminate people in close proximity, which is why it is important to maintain a certain physical distance between people, wear a mask and respect barrier gestures.
The finer drops or micro-droplets, on the other hand, remain suspended in the air for several hours; these are called "aerosols".
In a room, these aerosols gradually spread throughout the space. Their diffusion is comparable to that of perfumes or cigarette smoke.
The higher the concentration of aerosols in a room, the higher the risk of contamination.
Thanks to ventilation, the outdoor air combines with the aerosol-laden indoor air, which reduces the concentration of aerosols in the room, and thus the risk of contamination by the bio-pollutants (such as viruses) that the aerosols are likely to contain. This makes it possible to limit the risk of serious respiratory diseases.
5. How do you know if the ventilation is adequate?
To determine whether then ventilation in a room is adequate, we can measure the CO2 concentration. This is an indicator of whether ventilation rates are appropriate for the number of people and their activity. For example, a high CO2 concentration means that fresh air requirements are not being met, and that it is necessary to increase mechanical ventilation rates, open windows and doors, or stop any activities to allow the air to be replaced.
6. How do you measure CO2 concentration in a space?
You can measure CO2 concentration with a CO2 meter.
To obtain a set of representative measurements of the CO2 concentration in the room, take at least three (3) measurements of the CO2 concentration (expressed in ppm) for each activity carried out in the room, and calculate the average of these three measurements.
For the measurements to be representative, it's important to take them when the number of participants is at its maximum and the activity has been at least 50% completed (to allow the CO2 concentration to stabilise).
7. How do you measure ventilation rates?
The correct measurement of mechanical ventilation rates requires suitable equipment and specific skills. These measurements must be carried out by companies specialising in the measurement of mechanical ventilation rates and recognised to carry out such measurements in compliance with the NBN EN 16211 standard.
8. Are there any recommended ventilation rates?
There is no threshold value for ventilation rate, air replacement rate or CO2 concentration above which the risk of contamination by viruses or other types of pollutants can be excluded.
The more intense and regular the ventilation, the lower the risk.
This is why we must strive to achieve a CO2 concentration rate indoors that is comparable to that of the outdoor air (i.e. approximately 400 ppm).
The Law of 6 November 2022 defines two (non-mandatory) reference levels of ventilation rates for indoor air.
- A reference level of 25 m³/h of fresh outdoor air per person provides a CO2 concentration equal to or less than 1,200 ppm,
- A reference level higher than 40 m³/h of fresh outdoor air per person provides a CO2 concentration equal to or less than 900 ppm.
These reference levels are consistent with those of the Code of Well-being at Work and have been defined for a situation corresponding to a "normal" type of activity.
This minimum ventilation rate must be higher for intense activities, since the production of CO2 and the production of aerosols (and therefore the breathing of these aerosols) are then higher. It must also be higher if the number of people present increases, or if the nature of the activities is itself a source of pollution (for example, by producing fine particles).
9. How can I find the right ventilation rates for my space and activity?
You can find the procedure in Annex 1 of the Practical guide to preparing a risk analysis and action plan.
10. Can I set my own reference level?
Yes, you can select a CO2 concentration value and calculate the rate required to reach this concentration. You can find the procedure in Annex 1 of the Practical guide to preparing a risk analysis and action plan.
11. As the operator of a space covered by the Law of 6 November 2022, what are my responsibilities regarding the maintenance of the ventilation systems present?
As the operator, you are responsible for ensuring that the mechanical ventilation systems in place are in good working order, and for taking the necessary measures to ensure that these systems are ready for use at all times.
To do this, you must ensure that these ventilation systems are serviced by a person authorised to do so, taking into account the recommendations of the manufacturer and installer of your ventilation system.
The risk analysis must include at least the following information:
- Indication of whether or not there is an active maintenance contract for the ventilation system present;
- Name of the company with which the maintenance contract has been concluded;
- Frequency with which the ventilation system is serviced by the maintenance company (every ... months)
12. As the operator of a space covered by the Law of 6 November 2022, do I have to inform the public of the rates that my ventilation system can achieve?
As the operator, you are responsible for informing the public about the quality of the indoor air present, making this information available to the public on request.
You can provide two types of information on the air quality in the space:
• Either the values measured by the air quality meter, including at least the CO2 concentration;
• Or the rates that the ventilation and/or air purification system present can achieve.
You may therefore choose to inform the public of the values measured by the air quality meter instead of the rates that the ventilation system can achieve.
13. If I choose to publish the rates that the ventilation system can achieve, what information should I share with the public?
If there is at least one ventilation system in the space, you must indicate:
• the total outdoor air flow that can be reached in this space;
• the maximum number of people allowed in the space;
• the total outdoor air flow that can be achieved per person in this space at this nominal occupancy (i.e. the maximum expected number of people in the room);
• whether the ventilation system is managed and checked at regular intervals;
• the date on which the last ventilation system inspection was carried out.
14. What action should I take if it's not possible to inform the public?
If, for whatever reason, it is not possible for you to inform the public, you should state in your risk analysis the reasons why you are unable to provide either of these two types of information. You are also invited to describe in your action plan the measures to be taken to ensure this information can be shared with the public in the future.
15. Are there any spaces that are exempt from this requirement to inform the public?
Yes. Any space with a surface area of less than 15 m² and/or where members of the public are present for less than fifteen minutes is exempt from this requirement.
16. Is ventilation a good idea in these times of high energy prices?
Energy consumption remains an important point of attention. Maintaining a CO2 concentration in indoor air below a threshold of 1,200 ppm and a minimum ventilation rate of 25 m³/h, for example, does not result in a large increase in consumption PROVIDED that the ventilation rate is adapted to the number of people in the room and/or the CO2 concentration measured.
From an energy point of view, it is beneficial to have, if possible, a system with heat recovery and a demand control system. The demand control system automatically increases and decreases the ventilation rates depending on whether there are more or fewer people in the room and therefore depending on the CO2 concentration measured by the CO2 meter. Heat recovery involves the use of a heat exchanger built into the ventilation system that can achieve an efficiency level of 80% or more.
17. Are there any quality criteria for ventilation systems?
There are no specific technical or quality requirements for ventilation systems. It is recommended that the system be tested on delivery to check that the intended rate is achieved.
However, attention should be paid to the equipment's acoustics, as it is important to avoid "cutting off" the mechanical ventilation (or air purification) in the rooms because the noise is considered excessive. However, if the facility has to be shut down, it is important to monitor the CO2 concentration to ensure that it remains as low as possible, preferably below the recommended limits (below 900 ppm if possible and not exceeding 1,200 ppm). If the CO2 concentration exceeds these thresholds, it is strongly recommended that the ventilation system be reactivated to limit the risk of contamination.