Passive Monitoring

Passive monitoring methods provide a cost-effective solution for monitoring air quality at locations where continuous monitoring is not practical. 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. No active movement of air through the sampler is necessary.

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 a laboratory. Sulphur dioxide, nitrogen dioxide, ozone, hydrogen sulphide and volatile organic compounds are common pollutants monitored using passive samplers.

A major advantage of using a passive sampling system is that a network of multiple samplers can be used over a large area to determine the spatial variation of pollutant levels. Passive samplers are also useful for looking at long-term trends of air pollutants at specific locations. However, since sampling is conducted over a period of about one month, events that last for a short time period, such as one hour, may be "averaged out".

	Passive Monitoring Passive monitoring methods provide a cost-effective solution for monitoring air quality at locations where continuous monitoring is not practical. 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. No active movement of air through the sampler is necessary. 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 a laboratory. Sulphur dioxide, nitrogen dioxide, ozone, hydrogen sulphide and volatile organic compounds are common pollutants monitored using passive samplers. A major advantage of using a passive sampling system is that a network of multiple samplers can be used over a large area to determine the spatial variation of pollutant levels. Passive samplers are also useful for looking at long-term trends of air pollutants at specific locations. However, since sampling is conducted over a period of about one month, events that last for a short time period, such as one hour, may be "averaged out".