Pollutants are numerous, and air quality monitoring as we know it (regulated by the authorities) is typically based on the main pollutants which can affect health or the environment. The pollutants of interest are representative of releases from the primary sources of pollution such as traffic and industry, or for indoor air quality because of the release of vapours and odours from building materials. Our sensors Cairsens can measure and monitor most of those pollutants.
In France, air quality monitoring is mandatory and achieved by public associations dedicated to this field, the AASQA. In 2005, the World Health Organization (WHO) set guidelines for pm2.5 and pm10 particulate matter and for the following gases: ozone, nitrogen dioxide and sulfur dioxide. Many countries including the United States of America are required to measure additional parameters. For example, in the United States of America, the Clean Air Act requires EPA (Environmental Protection Agency) to set National Ambient Air Quality Standards for six common air pollutants. They are particle pollution (often referred to as particulate matter), ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. EPA calls these pollutants “criteria” air pollutants because it regulates them by developing human health-based and/or environmentally-based criteria (science-based guidelines) for setting permissible levels.
O3/NO2 – Ozone and nitrogen dioxide
From the oxidizing gas family, ozone and nitrogen dioxide are the most common pollutants in the cities and their surroundings. They will impact the human health by irritating the bronchia, if not the eyes for ozone.
Ozone is considered a secondary pollutant, consequent to the transformation of oxygen from the solar UV on contact with nitrogen dioxide (NO2) and hydrocarbons (HC). Hence it generally appears at a certain distance from emissions areas of those latest pollutants (NO2 and HC), as the transformation requires some time.
Nitrogen dioxide is linked to traffic, or also from urban heating. Another source is the oxidation of the nitrogen monoxide emitted by the ozone itself. Both being closely linked, we measure this two pollutants through one and only sensor, and we display only one unique value for both of them (no difference made between the two).
NO2 – Nitrogen dioxide
As detailed above, nitrogen dioxide is mainly caused by traffic and urban heating (20%), it can indeed be interesting to measure only this gas in order to monitor the impact of those actitivities directly for example.
CO – Carbon monoxide
This gas is also coming from the incomplete combustion of various combustibles (gas, fuel, coal, wood), and notably the traffic for example. It also measured in industrial sites monitoring involving combustion in their process.
CO2 – Carbon dioxide
Naturally present in the atmosphere at around 390ppm, it is today the main indicator in indoor air quality. Indeed, a poor aeration in an inhabited building (and thus the lack of air renewal) will increase the CO2 concentration as it is what we exhale.
H2S/CH4S – Hydrogen sulfide and methylmercaptan (methanethiol)
Hydrogen sulfide (H2S) and methylmercaptan (CH4S) are both from the family of the total reduced sulfur compounds. They are easily recognizable by their strong odor (rotten egg for H2S, rotten cabbage for CH4S) which will be detectable at really low concentrations by the human nose.
They are mostly produced by industrial activities : extraction and treatment of gas/fuel, wastewater treatment plants, tanneries, paper mills, etc.
NH3 – Ammonia
Composed by nitrogen and hydrogen, this gas has a pungent odor, and can be irritating when its concentration in the air increases.
It is widely used (one of the most synthetized solvents in the world) in industry, as a refrigerant gas, to synthetize medicaments or also fertilizers. It is also one of the odorous gases produced by the decomposition of used water in wastewater treatment plants.
SO2 – Sulphur dioxide
Mostly produced by industrial acitivites, and notably thermal power stations, it is also produced by heating. It is created by the combustion of gas, fuel, coal… and is directly linked to their concentration in sulphur.
nmVOC – Non methane volatile organic compounds
The family of volatile organic compounds is extremly wide, and contains in particular the BTEX (Benzene, Toluene, Ethylbenzene, Xylene). Derived from the evaporation of combustible or exhaust gas, they are also produced by various industrial activities (refineries, wastewater treatment plants, etc.). Our sensor measure all the non-methane volatile organic compounds.
CH2O / Organic solvents – Formaldehyde and other organic solvents
We find those pollutants essentially in the indoor spaces, as they are emitted by construction-related materials (paint, adhesive, mural coating, ceiling, wood, etc.). They are, with the CO2, a key indicator of indoor air quality.
PM – Particulate matter
They are microscopic particulate, as their size is 10 times smaller than the thickness of a human hair for the PM10, or the size of a bacterium for the PM2.5. Their effect on health, both on pulmonary and cardiovascular levels, have been highlighted by the WHO.
The emitting sources for such pollutants are again industrial or linked to the traffic, the heating being also a known source.