4. The role of aerial metrology in assessing biological risks

4.1 Airborne micro-organisms

Ambient air includes micro-organisms of environmental origin (soil, water, plants...) and micro-organisms emitted by humans or animals. Outside, depending on environmental conditions, there can be from a few to several hundred micro-organisms per cubic metre. In a normally ventilated room, germs from the outside atmosphere are found alongside germs from sources of emissions (people, processes, etc.) located in the room in question. The greater the number of individuals emitting micro-organisms, the greater the degree of contamination in confined air. Depending on various factors (work activity, ventilation rate, temperature, etc.), the number of germs can vary from a few thousand to tens of millions per cubic meter.

Many infectious...