PAB indoor air quality measurement

The obligation to measure the quality of indoor air in certain PAB - particularly in collective childcare facilities - introduced by the Grenelle 2 law, has been applicable to nurseries and schools since January 1, 2018 (Decree No. 2015-1000 of August 17, 2015). Since 2020, it has applied to secondary schools and since 2023, to all other schools. Three substances considered as priorities by the scientific community must be measured and analyzed: formaldehyde, benzene and carbon dioxide. 

Monitoring of indoor air quality in public buildings

Many chronic diseases such as asthma or allergies are linked to the degradation of indoor air quality in public buildings. The analysis of the air quality in the PABs consists in measuring and controlling the exposure levels of some very toxic gases such as formaldehyde, benzene and carbon dioxide. If the facility in question is in close proximity to a dry cleaning facility, tetrachloroethylene (perchloroethylene) will also need to be measured and analyzed.


Formaldehyde is a substance that irritates the nose, eyes and respiratory tract, emitted in particular by certain construction materials, certain glues or cleaning products. It is a toxic gas by inhalation (R23), by skin contact (R24), by ingestion (R25) and may cause burns (R34). The IARC* has identified a link between exposure to formaldehyde and the risk of cancer (R40).


Benzene is a substance found in fuels, particularly unleaded gasoline, and therefore in exhaust gases. Classified as a category 1 carcinogen (R45 and R49) by the IARC*, it is also likely to cause hereditary genetic damage (R46). In case of prolonged exposure, by ingestion, inhalation or skin contact, benzene has serious health consequences (R48/23/24/25).

Carbon Dioxide

Carbon dioxide (CO2) is a gas representative of the level of confinement. Links have been found between poor ventilation - resulting in high levels of CO2 - and decreased academic ability in children tested through logic, literacy and numeracy exercises. It is an odorless and colorless gas with asphyxiating properties that replaces oxygen in the air.


Perchloroethylene is a widely used solvent, particularly as a dry cleaning solvent in laundry. It is also used as a degreasing agent, in the treatment of textiles, or in printing. Classified as a probable carcinogen of category 2A (R40) by the IARC*, it is also likely to cause irritation of the respiratory tract and eyes, dizziness and headaches. 

*IARC: International Agency for Research on Cancer (part of the WHO World Health Organization)

Punctual or continuous monitoring of pollutants?

Punctual monitoring of formaldehyde & benzene

I - The analyses of the samples are performed in accordance with the good practices in force, according to the methods specified, as the case may be, in paragraphs II and III. The realization of analyses in accordance with the standards mentioned in 1° and 2° of article 6 are presumed to be in conformity with these good practices, respectively, for formaldehyde and benzene. 

II - The analysis of formaldehyde is done by chemical desorption, followed by an analysis by high performance liquid chromatography coupled with an ultraviolet detector. The analysis method respects a quantification limit of less than 2 μg/m³ for a sampling period of 4.5 days. 

III - The analysis of benzene is carried out by thermal desorption, followed by an analysis by gas chromatography coupled to a detection by flame ionization or mass spectrometry. The analytical method respects a limit of quantification of less than 0.4 μg/m³ for a sampling period of 4.5 days. 

Source: Article 7 (deferred) decree n° 2015-1000 of August 17, 2015.

Continuous measurement of CO2 (carbon dioxide)

I - The continuous measurement of carbon dioxide for the evaluation of air containment is performed with an apparatus operating on the principle of non-dispersive infrared absorption spectrometry, meeting the following characteristics:

  • Minimum measurement range: 0 to 5000 ppm ; 
  • Uncertainty at 20 °C and 1013 mbar ± (50 ppm + 3% of reading) ; 
  • Resolution 1 ppm 
  • Response time t63 200 seconds ; 
  • Measurement frequency: 1 point every 10 minutes; 
  • Data recording capacity for a minimum of eight days on a ten-minute time step. 

II - The carbon dioxide measurement results are used to calculate a containment index according to the method described below. 

The containment index is calculated from a continuous measurement of the carbon dioxide concentration in the air, expressed in parts per million (ppm), with a recording time step of ten minutes.

The continuous measurement is carried out only during periods when the number of students or children actually present in the room is higher than 0.5 times the theoretical size of the classroom or activity room and lower than 1.5 times the theoretical size of the room. The CO2 concentrations corresponding to the selected periods are then separated into three classes: 

  • Values below 1,000 ppm; 
  • CO2 measurements between 1,000 and 1,700 ppm; 
  • Concentrations above 1,700 ppm. 

Source: Article 8 (deferred) decree n° 2015-1000 of August 17, 2015