What is particle filtration efficiency

Different types of filters such as fiber filters, membrane filters and fabric filters can be used to remove particles from air flow. The removal of the particles by the filter happens via different mechanism including interception, impaction, diffusion and electrostatic attraction. Typically, the effectiveness of the filter is described with a filtration efficiency value, which is the efficiency of the filter to remove particles from the air flow in percentage (0–100 %). The amount of removed particles by the filter depends on the filter properties and is typically highly dependent on particle size. Because of this size dependence, it is important to evaluate the filtration efficiency separately for different sized particle to properly understand the operation of the filter material.

How to measure particle filtration efficiency

Dekati® measurement solutions for particle filtration efficiency (PFE) research and testing include both real-time instruments and gravimetric cascade impactors for particle size distribution and concentration measurements. Our particle measurement solutions have been successfully used in filter efficiency testing and research for over 25 years and today, our instruments are used globally by thousands of customers both in research and industry to measure different properties of airborne particles <10 µm.

Dekati® measurement instruments provide more detailed information than what filtration standards (EN 149, EN 13274, EN 14683) require. Our measurement solutions provide options for real-time monitoring of particulate mass, number, or the lung-deposited surface area (LDSA) of the particles, and for total concentration and particle size distribution measurements. Our instruments additionally enable gravimetric and chemical analysis of size classified particles with cascade impactors, PM10 – 2.5 – 1.0 measurements and real-time particle size distribution measurements. The instruments operate in a wide dynamic range enabling the use of the same instrument for measurements before and the filter.

Dekati® instruments are used for testing and research of

• Air cleaning filters
• Facemasks including N95, N99, N100, FFP1, FFP2 and FFP3 masks
• Electret filters
• Ventilation filters (HVAC testing)
• Oil mist filters
• Blow-by gas filters in automotive industry
• Baghouse filters and ESPs in energy production and other stationary sources
• Other industrial filters

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Assessing facemasks to protect against COVID-19 using ELPI®+ at Instituto Nacional de Técnica Aeroespacial (INTA), Spain. Image courtesy of Victor Achilla (archillapv@inta.es).