What is Arrestance, Dust Spot Efficiency 80-85%, MERV13?

Dust Arrestance refers to filtration by dust weight. Rationale: Larger particles are heavy, thus Filtration efficiency of larger particles > 10um will be more relevant.  In order not to confuse the efficiency with dust spot efficiency below, this is always referred as "Arrestance" which is in the pre or primary filters range.

Dust spot efficiency refers to filtration of a range of particles of mean size 1um. This is usually referred to secondary filters. It is widely used as it is still relevant in all countries.

MERV : Minimum Efficiency Reporting Values. This US standard is ASHRAE 52.2 :1999 which is dervied to categorise filters. It has 3 ranges, E1: 0.3-1um, E2:1.0-3.0um, E3: 3.0-10.0um. However, it is found to be not useful for prefilters range as they do not consider particles >10.0um which forms big part of the dust, so Arrestance should still be used. As the HEPA filtration has IEST:RP and cleanroom standards, it is not useful for categorising HEPA filters.


MERV13 ~ 80-85% dust Spot Efficiencies ~ F7 ~ Arrestance >99%

MERV14 ~ 90-95% dust spot efficiencies = F8 ~ Arrestance >99%

MERV15 ~ >95% dust spot efficiencies = F9 ~ Arrestance >99%


More info can be found in the catagloue/technical specifications.


Air Filtration classifies filters by measuring filtration percentage using dust particles. Mainly three types of classifcations, Primary/Pre , Secondary and HEPA.

Primary/Pre filters by Dust arrestance by weight (for bigger particles >10um).

Secondary Filters by Dust spot efficiencies in the particle range 0.3 to >10um.

HEPA filtration at mean particle size of 0.3um.

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