Similarly, the specified dust removal efficiency of an air filter will vary widely depending on the method of measurement. Two measurement methods are Dust Holding Capacity and Arrestance. Dust Holding Capacity is a measure of the weight of dirt a filter can hold before it reaches a predetermined final resistance. A filter with 100 grams dust holding capacity should last approximately twice as long as a 50 gram filter under the same conditions. Arrestance is a measure of air cleaning based on weight of dirt collected.
Dirt getting through the filter is what damages equipment.
Filter service life increases as the square of the increase in surface area. To improve the filter's life, reduce the flow rate through the filter media. In practice, all these axioms have some legitimacy, but often much more is involved. The accompanying graph depicts the effects of increasing filter surface area on the service life of the filter. The MAX line shows maximum expected increase in filter life due to an increase in filter area, under optimum operating conditions.