The values displayed by indoor air quality testers are often for the uninitiated a series of numbers and acronyms that are not always understandable.

By following this guide you will become an expert on IAQ and air analyzers. VOC, CO2, PM25, PM10, formaldehyde, CO, we will break down the essentials of these values for you, the standards, the alert thresholds and their effects on health. 

Symbol : CO2

Unit of measurement: ppm

Carbon dioxide (CO2) is a natural component of the air we breathe; it is a colourless and odourless gas that is naturally produced by living things during breathing for example, or also by the combustion of various products.

CO2 at high levels in a room is an indication of insufficient ventilation for the number of occupants in the room. The quantities of CO2 detected are often misinterpreted and confused with carbon monoxide (CO) which is more dangerous. It is only in very high concentrations in the air that CO2 becomes harmful.

Key values for CO2 in the air :

Symbol: CO

Unit of measurement: ppm

Carbon monoxide (CO) is a toxic gas that is extremely dangerous to our health. It is colourless, odourless and non-irritating. It cannot be detected without equipment.

It is an asphyxiating gas which, once it has entered the lungs, takes the place of oxygen in the blood. In case of exposure, death by carbon monoxide poisoning can occur within an hour. Symptoms that should alert you are: headaches, nausea and vomiting.

In indoor air, its presence results from incomplete combustion of the fuel used: wood, gas, coal, oil, candles, petrol, etc.

The values of CO in the air to remember :

Symbols : COV , VOCs , TVOC , TCOV

Unit of measurement :   µg /m3 ou µg.m-3, mg/m3

COV(Volatile Organic Compounds) in indoor air are a collection of more than 165 microscopic airborne chemical or organic substances. Common sources of COV indoors are: cooking, smoking, DIY, cleaning, household appliances, furniture and pets.

COV have undesirable short-term effects: discomfort, odours, drowsiness, irritation, but also health effects with the development or aggravation of respiratory pathologies and allergies. In the long term, COV are also the source of certain cancers and degenerative diseases.

COV are all different and have different maximum concentrations depending on the molecule. Thus, global monitoring of COV cannot replace precise monitoring of the molecules according to the sources of pollution in the place. Nevertheless, the decree n° 2011-321 of 25 March 2011 defines some rules on the general rate of admissible COV.

Relevant values for COV in air :

Symbols : PM10, PM25, PM2.5, PM2,5

Unit of measurement :  µg /m3 ou µg.m-3

Microparticles or fine particles are mainly generated by heating, transport and industry, but they also come from spores, certain aerosol products or combustion by-products (tobacco, candles, cooking, etc.). It should be noted that some COV are also fine particles.

They are generally referred to as PM10 (particles smaller than 10 μm) and PM2.5 (smaller than 2.5 μm). However, indoor air also contains a large number of ultrafine particles: PM1 (smaller than 1 μm).

Each particle penetrates the body in a different way depending on its size and composition, with increasingly dangerous areas of effect as the size of the particles decreases.

PM10 values to remember :

VALUES TO REMEMBER FOR PM2.5

Symbols : Formaldehyde, HCHO,

Unit of measurement: μg/m³, mg/m³ ou ppm

Formaldehyde is a colorless, suffocating, flammable gas and classified as a carcinogen. It is frequently present in indoor air. Formaldehyde is used as a disinfectant, as a fixative and as a binder in resins (do-it-yourself products, maintenance, wall and floor coverings, furniture, plastics...). It is found in large quantities in the veterinary, cosmetic, medical, industrial and agricultural sectors...

The values to remember for formaldehyde in the air :