Air Filters Efficiency Classification

ASHRAE 52.2: Filter testing was originated from America in 1930 (ASHVE and AFI code). It was then reviewed and modified in 1967 and 1968. ASRHAE collaborated with American National Standard Institude (ANSI) in 1992 to create ASHRAE-ANSI 52.1. Finally updated to ASHRAE 52.2 in 2007.

EUROVENT 4/4 and 4/5: Eurovent 4/5 was established in 1974 by modifying existing ASHRAE 52-68 to suit the applications in Europe. Eurovent 4/5 is catered for primary and secondary filter while Eurovent 4/4 is catered for high efficiency filters

EN 779: It was the first European’s Air filter test method in 1993, built on the foundations of Eurovent 4/5. This standard was modified later in 2002 and 2012. Only covers primary and secondary filters.

EN 1882: It is the improvisation from Eurovent 4/4 in 1998. This standard was modified only once in 2010. It covers high efficiency filters (E10 and above).


CLASSIFICATIONArrestance or Dust Spot EfficiencyUS ASHRAE 52.2European Union EN779 ClassTypical Controlled ContaminantApplication
PRE Filter
(G Class)
AFI MERV 1G1AmParticle bigger than 10.0µm
(Spanish moss)
(Dust mites)
(Sanding dust)
(Spray paint dust)
(Textile fibers)
Gross filter, domestic
and commercial
AFI 65%-70%MERV 2G265%≦Am
AFI 70%-75%MERV 3
AFI 75%-80%MERV 4
AFI 80%-85%MERV 5G380%≦AmParticle size within 3.0µm-10.0µm
(Hair spray)
(Cement dust)
(Powdered milk)
industrial, paint shop
AFI 85%-90%MERV 6
NBS 25%-30%MERV 7G490%≦Am
NBS 30%-35%MERV 8
(F Class)
NBS 40%-45%MERV 9F540%≦EmParticle Size within 1.0µm-3.0µm
(Lead dust)
(Milled flour)
(Coal dust)
(Auto emissions)
(Nebulizer drop)
(Welding fumes)
IAQ concerned
commercial &
industrial, medical
NBS 50%-55%MERV 10
NBS 60%-65%MERV 11F660%≦Em
NBS 70%-75%MERV 12
NBS 80%-85%MERV 13 F780%≦EmParticle size within 0.3µm-1.0µm
(All bacteria)
(cooking oil)
(Most smoke)
(Copier toner)
(Most face powder)
(Most paint pigments)
IAQ concerned
commercial, industrial,
medical, food etc
NBS 90%-95%MERV 14F890%≦Em
NBS>95%MERV 15F995%≦Em
HEPA Filter
(H Class)
≧95% at 0.3µmH10≧85% at MPPSParticle size bigger than 0.3µm (Virus [unattached])
(Carbon dust)
(Sea salt)
(All combustion smoke)
(Radon progeny)
All types of cleanrooms
≧98% at 0.3µmH11≧95% at MPPS
≧99.97% at 0.3µmTYPE A
≧99.99% at 0.3µmTYPE CH12≧99.5% at MPPS
≧99.995% at 0.3µmH13≧99.95% at MPPS
≧99.999% at 0.3µmTYPE DH14≧99.995% at MPPS
ULPA Filter
(U Class)
≧99.9995% at 0.12µmTYPE FH15≧99.9995% at MPPSParticle size bigger than 0.12µmsuper cleanroom
≧99.99995% at 0.12µmH16≧99.99995% at MPPS
≧99.999995% at 0.12µmH17≧99.999995% at MPPS

1. AFI : American Filter Institute

2. NBS : National Bureau of Standards

3. ASHRAE : American Society of Heating Refrigerating & Air-conditioning Engineers

4. MERV : Minimum Efficiency Reporting Value

5. MPPS : Most Penetrating Particle Size

6. HEPA : High Efficiency Particulate Air Filter

7. ULPA : Ultra Low Penetration Air Filter

8. Am : Average Arrestance Efficiency for Coarse Filters

9. Em : Average Efficiency for Fine Filters

10. IEST : Institute of Environmental Sciences and Technology


What is the significance of ASHRAE 52.2 in air filter testing?
ASHRAE 52.2 is a widely recognized standard for testing air filters, originating from the United States in 1930. It has undergone several revisions, with the latest update in 2007. ASHRAE 52.2 provides a comprehensive framework for evaluating air filter performance, including parameters such as particle removal efficiency, pressure drop, and dust holding capacity. This standard serves as a benchmark for the air filtration industry, ensuring that air filters meet specific criteria for efficiency, safety, and performance.
How does Eurovent 4.5 differ from Eurovent 4.4 in terms of filter classification?

Eurovent 4.5 and Eurovent 4.4 are two distinct standards developed by Eurovent, a European association of air conditioning and refrigeration manufacturers. Eurovent 4.5 is designed for primary and secondary filters, while Eurovent 4.4 is specifically tailored for high-efficiency filters. The main difference lies in the filter efficiency classification, with Eurovent 4.5 focusing on lower to medium efficiency filters and Eurovent 4.4 catering to higher efficiency filters. This distinction enables manufacturers to design and test filters according to specific application requirements.

What is the primary difference between EN 779 and EN 1882 air filter standards?

EN 779 and EN 1882 are two European standards for air filter testing, with distinct focuses. EN 779, introduced in 1993, is primarily designed for primary and secondary filters, while EN 1882, introduced in 1998, is focused on high-efficiency filters (E10 and above). The key difference lies in the filter efficiency classification and the testing procedures employed. EN 779 is more geared towards general ventilation applications, whereas EN 1882 is suited for critical applications requiring high-efficiency filtration.

How have revisions to EN 779 and EN 1882 impacted air filter testing and classification?

The revisions to EN 779 (2002, 2012) and EN 1882 (2010) have introduced significant changes to air filter testing and classification. These updates have refined the testing procedures, expanded the scope of filter types, and improved the accuracy of filter efficiency classification. The revisions have also ensured that air filters meet increasingly stringent requirements for indoor air quality, energy efficiency, and environmental sustainability. As a result, manufacturers must adapt their filter designs and testing protocols to comply with the revised standards.

What are the implications of ASHRAE 52.2, Eurovent, and EN standards on global air filter markets?

The ASHRAE 52.2, Eurovent, and EN standards have far-reaching implications for the global air filter market. These standards influence filter design, testing, and classification, ultimately affecting the performance, safety, and energy efficiency of air filtration systems. Manufacturers must comply with these standards to ensure their products meet regional and international requirements. This compliance drives innovation, improves product quality, and enhances customer confidence in air filter products. Furthermore, the standards facilitate trade and commerce by providing a common language and framework for air filter specifications and performance.