Passive monitoring is primarily used for monitoring air quality at locations where continuous monitoring systems have no access. Passive sampling devices can monitor air pollutants without the need for electricity, data loggers or pumps. Passive sampling devices are lightweight, portable and relatively simple to operate.

Passive sampling involves the exposure of a reactive surface to the air, and transfer of the pollutant occurs by diffusion from the air to the surface. The surface consists of a solid chemical compound or a filter that is impregnated with a reactive solution. Samplers are typically exposed for periods of one month, and analysis is done in an accredited laboratory.

Sulphur dioxide (SO2), nitrogen dioxide (No2), ozone (O3), hydrogen sulphide (H2S) and volatile organic compounds (VOC’s) are the most common pollutants monitored using passive samplers.

Since sampling is conducted over a period of one month, occasional intervals of high level concentrations usually go unnoticed because the readings are averaged for the whole month.

Diagnostic Engineering Inc. supplies Stand Alone Air Quality Monitoring to complement the Passive Sampling Networks. The use of the Active Air Monitoring System helps to determine “what actually” occurred over the one month sampling period. The active system breaks down all readings over smaller averaging periods (Eg. 5 minutes, 15minutes, 1hour, 24hour, etc…), which will show if any exceedences of the Ambient Air Quality Guidelines occurred. This complementary system benefits in determining if one or several high concentration periods occurred, but went undetected.