Flow measures particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2) and volatile organic compounds (VOCs).
Particulate Matter (PM10 and PM2.5)
What is it? Particulate matter consists of small solid particles that can penetrate the airways and lungs. The finest particles can even bind to blood vessels. PM10 (PM standing for particulate matter) refers to particles smaller than 10 microns in diameter and PM2.5 for those smaller than 2.5 microns.
Where does it come from? Particulate matter comes from human activity such as road traffic or energy transformation and from natural phenomenons such as volcanic eruptions and even sand on a windy beach. The PM concentration in the air varies significantly with elements like temperature and wind speed.
What are the risks? Fine particles trigger nasal allergies. Chronic exposure is a risk factor for cardiovascular and respiratory diseases as well as lung cancer.
Nitrogen dioxide (NO2)
What is it? NO2 is a suffocating and irritating gas that can be easily recognized thanks to its red-brown color. It also has a pungent odor.
Where does it come from? Mainly from combustion (heating, electricity generation, vehicle and boat engines). 50% of NO2 emissions are from road traffic.
What are the risks? NO2 may cause bronchitis and asthma, especially for children. A high concentration of NO2 may also contribute to decreased lung function.
Volatile Organic Compounds (VOC)
What are they? These are molecules made mainly of carbon and found as gases in the air we breathe. They are very volatile and can spread a long way away from their emission source.
Where do they come from? Outdoors: VOCs are emitted by road traffic, industries, the residential sector, and also vegetation. Indoors: Cleaning and DIY products are important emitters of VOCs, as well as some floor and wall coatings.
What are the risks? In cases of high concentration, VOCs can cause irritation and decreased breathing capacity. Some VOCs are classified as carcinogenic.