The performance of a filter is generally evaluated based on four parameters. These include:
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Contaminant removal efficiency
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Contaminant holding capacity
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Resistance to airflow
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Safety with regard to support or spread of fire and smoke
Contaminant removal efficiency is tested by challenging the filter with contaminant on the upstream side and measuring the residual contaminant on the downstream side of the filter after the air has passed through the media. Various methods and instruments have been developed for moving the air through the filter, holding the filter, generating and dispursing the challenge, and measuring the challenge on the upstream and downstream side of the filter.
Contaminant holding capacity is determined by measuring the mass of contaminant removed before the filter reaches its maximum differential pressure in the case of particle filters or before the contaminant breaks through the filter in the case of a gaseous filter.
Resistance to airflow is determined by measuring the pressure of the air upstream of the filter and downstream of the filter and comparing those values. The value of resistance to airflow must be accompanied by the value of airflow velocity in order to truly understand the performance of the filter.
Safety in a situation where a filter is exposed to flame is measured by its support of fire when no other fuel source is present (the filter is therefore a fuel source), the amount of smoke generated by the filter, and the release of sparks by the filter when exposed to the heat of a flame.