Belgian legislation on indoor air quality

Back to Work – the measures to be taken to limit COVID-19 contamination

The return to the office will gradually become a reality. As the COVID-19 crisis drags on, it is more than necessary to put in place measures to limit the risks in the office.

Practical recommendations on office ventilation and the use of CO2 sensors have been published by the federal public service Employment in Belgium.


These recommendations recall the legal threshold for a maximum CO2 concentration of 900 ppm (or 500 ppm above the outdoor CO2 concentration). If as part of the fight against Coronavirus contamination, it has been shown that it increases sharply in unventilated indoor places, there is no scientific study defining a CO2 threshold beyond which the risk increases. strongly. As a reminder, however, it has long been established that there is a direct relationship between indoor air pollution (and therefore the lack of ventilation) and the CO2 concentration.

The recommendations of the federal public service employment are therefore, in any case to keep the concentration below 900ppm (legal threshold), but also to try to reduce this CO2 concentration to a threshold as close as possible to the outdoor CO2 concentration, namely around 400-450ppm.

The CO2 concentration is measured with a CO2 sensor. Maintaining this concentration at correct values ​​is done through good ventilation (natural – opening doors / windows, or mechanical – a ventilation system).

The recommendations of the Federal Public Employment Service are to place CO2 sensors in all rooms. And if this is not possible (budget…), to take regular one-off measurements.

If the CO2 concentration increases too much (and exceeds the legal threshold of 900ppm), the measures to be taken are:

  • Ventilate more, or increase the ventilation air flow (and limit / cut off air recirculation, to promote fresh air flow)
  • Limit (reduce) the number of people in the room affected by too high a concentration.
  • If this is not enough, set up an ambient air purification system.

The recommendations of the Federal Public Employment Service can be found here: