on rooms and on ventilation
In France, wastewater treatment plant comes under the specific pollution rooms category,"rooms in which dangerous or unpleasant substances are emitted as gases, vapours, solid or liquid sprays … "
This category has two characteristic values :
- short-term exposure limit values (VLE in French) : these are ceiling values measured of a maximum period of 15 minutes. Compliance with this limit prevents the risk of immediate or short-term toxic effects;
- average exposure limit values (VME in French) : measured or estimated over an 8-hour shift, these limits are intended to protect workers from long-term effects. The VME value can be exceeded for short periods providing the VLE value is not exceeded, when it exists.
Both VLE and VME are expressed as volume (ppm or parts per million), as weight per volume (mg·m–3) or as percentage per volume, knowing that :
Note: a device must also warn of any sensor system failure.
Many substances are subject to limit values. These limit values will be statutory requirements for some substances. For others, they are provided for guidance.
Table 2 quotes French VME and VLE values and compares them with the statutory figures applicable in the USA, Germany and Russia.
Note: as in the case of the mean exposure limit value (VME), MAK and TWA (time weighted average) shown as (T) are subject to a weighted average value over an 8-hour period. Values shown as (S), short term exposure limit or STEL, represent the mean weighted concentration over a 15 minutes period and must not be exceeded more than 4 times a day subject to a minimum elapsed time of 1 hour between occurrences.
french legislation on odours
Law of the 30th December 1996 on air and the rational use of energy detailed in article 2 of said law :
"Shall be regarded as atmospheric pollution: the direct or indirect introduction by Man into the air or into confined spaces of any substance likely to jeopardise human health, biological resources and ecosystems …, to create excessive olfactory nuisances". In the absence of any definition of what constitutes maximum olfactory intensity, the legislator has therefore left it up to clients to set their own requirements accordingly.