4. Emission sources and determination of emissions

Atmospheric emissions come from a wide variety of sources. Irrespective of the intensity of the emission, which depends on the source's activity, it is released in a variety of ways.

• Piped stationary sources

  The effluent passes through a physically materialized enclosure. Gas flow and pollutant concentration, and hence emissions per unit of time, can therefore generally be estimated fairly accurately.

• Fugitive stationary sources

  Non-channelized emissions due to leaks (pumps, valves, flanges), or to specific operations (loading, furnace defueling, tank evaporation, etc.) occur more or less randomly. They are characterized by poorly identified release conditions (flow delimitation, concentration).

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