Calculation using average emission factors

Calculation definition   Launch calculation

The simplest approach to evaluate fugitive emissions on equipments is to use the average emission factors. The only unit-specific data that are required are usually simple to collect:

  • The number of each type of component in the unit (valve, connector, etc.),
  • The service each component is in (gas, liquid, etc.),
  • The time period each component was in that service.

If a speciation is to be performed or if the stream doesn't contain only organic components (but else other products or methane for refineries), VOC concentrations data in the stream may be necessary for a good characterisation of emissions.

The use of the average emission factors is a global approach valid for estimating emissions from a population of equipment but is not adapted for estimating emissions from an individual piece of equipment.

In the average emission factors evaluation method, leak concentration measurements are not required but the results can not be use to identify leakage equipments (for correcting action for example). The method provides a general indication of equipment leak emission rates from equipment in the process unit but doesn't take in consideration the site-specific conditions (that can have considerable influence on leak rates from equipment).

The average emission factors can be use for process units on following sites:

  • SOCMI (Synthetic Organic Chemical Manufacturing Industry),
  • Petroleum refineries,
  • Petroleum marketing terminals,
  • Oil and gas production facilities.


The SOCMI, marketing terminal, and oil and gas production operations average emission factors predict total organic compound emission rates, whereas the refinery average factors predict non-methane organic compound emission rates.

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