IEST vs EN 1822 HEPA Filter Classifications & Testing Methods

Amidst surging demand for air purification products, many resellers and distributors have recognized an opportunity to gain a foothold in the industrial, retail, and consumer air filtration markets. As the number of market competitors grows, confusion often arises when customers attempt to decode the nuances between various HEPA filter brands, terminology, and performance ratings.

If it says "HEPA filter", that's all I need to know, right?

Customers should know that the term "HEPA filter" represents a much wider swath of products spanning multiple groups and categories, each with its own standard of performance and efficiency ratings.

Numerous factors influence the extended performance and efficacy of HEPA filters and blowers. For example, gas filtration, velocity, particle characteristics, and filter media construction. Efficiency, ease of maintenance, peak power curve, and fan noise are additional considerations that require discussion when selecting a HEPA filtration system.

High Efficiency Particulate Air Filters (HEPA)

Commercial and Industrial HEPA Filtration

Commercial HEPA air filters capture both micro and macroparticles including allergens, germs, soot, dust, and organic materials. Industrial environments can present challenges for HEPA filter media when encountering high volumes of soot, smoke, dust, and powders.

Most industrial filtration designs also consider appropriate gas or molecular filters to remove gas or ionic compounds. Additional filtration systems are needed for removing hazardous, odorous, or nauseating gasses or fumes.

HEPA filters are not able to capture fumes or aerosol contamination, thus molecular filtration systems are needed to remove hazardous, odorous, or noxious fumes from the air.

Cleanroom HEPA Filters for Electronics, Biopharmaceuticals and Medical Device Manufacturing Environments

Submicron particles are typically the most problematic for cleanroom and electronics manufacturing facilities. In electronics and semiconductor manufacturing, a distinction is made between metallic and nonmetallic particles. Metallic particles are produced as artifacts of various etching, engraving, and soldering processes. Non-metallic particles consist of many contaminants including dirt, debris, cross-contamination, fibers, and human-borne contaminants such as hair, skin, or biological fluids.

A facility may choose different filter types at different stages of production. HEPA and ULPA filtration are prototypical for most cleanroom-rated environments. In less critical areas such as prep, cleaning, or final-packaged storage areas, larger-pore MERV filters or integrated pre-filters can provide a more energy-efficient and cost-effective option.

Continue: Cleanroom ULPA / HEPA Filter Definitions and Requirements

HEPA Filters for Medical and Biotech Facilities

In healthcare and medical environments, filtration solutions must address much larger droplets to prevent the spread of airborne respiratory droplets. Large and heavy particles are less likely to become buoyant and quickly settle on the floor or surfaces. On the other hand, extremely small particles are more likely to become airborne, but due to their size, carry a much smaller payload.

A singular virion suspended in the air is much less likely to carry an infection-causing payload when compared to a large droplet or mucous sample containing millions or billions of virions. For infectious disease control methods, airborne viruses and pathogens typically spread through exposure to much larger respiratory droplets. While it was originally theorized that SARS-COV-2 and similar respiratory viruses were primarily transmitted through droplets, continued research has demonstrated clear evidence of aerosolized transmission.

Particulate Matter (PM) Size Charts

EN 1822 HEPA Filter Classifications

Filters with class E, H, and U class ratings originate from European filter testing standards described within EN1822 standards.

There are three recognized filter groups described in the documentation provided by EN1822:2009.

  • Group E: EPA (Efficient Particulate Air Filter)
  • Group H: HEPA (High Efficiency Particulate Air Filter)
  • Group U: ULPA (Ultra Low Penetration Air Filter)

What is an H13 HEPA Filter?

According to EN1822:2009, HEPA filters are described with H-class ratings, either H-13 or H-14.

Many HEPA filter manufacturers and resellers have adopted product nomenclature that designates H13 ratings. An H13 rating is the minimum class requirement for HEPA filter standards in the US. Therefore, there is little technical difference in the performance of an H13, IEST Type F, and a True HEPA filter.

EN1822 Classifications

EN1822 Classification
Particle Size
for Testing
Global Values Local/Leak Values
Efficiency %
Penetration % Collection
Efficiency %
Penetration % Multiple of
Global Effiency %
E10 - ≥ 85 ≤ 15 - -  
E11 - ≥ 95 ≤ 5 - -  
E12 - ≥ 99.5 ≤ 0.5 - -  
H13 MPPS ≥ 99.95 ≤ 0.05 ≥ 99.75 ≤ 0.25 5
H14 MPPS ≥ 99.995 ≤ 0.005 ≥ 99.975 ≤ 0.025 5
U15 MPPS ≥ 99.9995 ≤ 0.0005 ≥ 99.9975 ≤ 0.0025 5
U16 MPPS ≥ 99.99995 ≤ 0.00005 ≥ 99.99975 ≤ 0.00025 5
U17 MPPS ≥ 99.999995 ≤ 0.000005 ≥ 99.9999 ≤ 0.0001 20

IEST Listed HEPA Filter Classifications

IEST-RP-CC001 Filter Classifications Chart

Particle Size
For Testing

Global Values Local/Leak Values
Efficiency %
Efficiency %
Multiple of
Global Efficiency %
A 0.3* ≥99.97 ≤0.03 - - -
B 0.3* ≥99.97 ≤0.03 Two flow leak test -
E 0.3* ≥99.97 ≤0.03 Two flow leak test -
H 0.1-0.2 or 0.2-0.3** ≥99.97 ≤0.03 - - -
I 0.1-0.2 or 0.2-0.3** ≥99.97 ≤0.03 Two flow leak test -
C 0.3* ≥99.99 ≤0.01 ≥99.99 ≤0.01 1
J 0.1-0.2 or 0.2-0.3** ≥99.99 ≤0.01 ≥99.99 ≤0.01 1
K 0.1-0.2 or 0.2-0.3** ≥99.995 ≤0.005 ≥99.992 ≤0.008 1.6
D 0.3* ≥99.999 ≤0.001 ≥99.99 ≤0.005 5
F 0.1-0.2 or 0.2-0.3** ≥99.9995 ≤0.0005 ≥99.995 ≤0.0025 5
G 0.1-0.2 ≥99.9999 ≤0.0001 ≥99.999 ≤0.001 10
* Mass median diameter particles (or with a count median diameter typically smaller than 0.2µm as noted above).
** Use the particle size range that yields the lowest efficiency.

IEST rated HEPA filters are deemed suitable for cleanroom use as described in universal cleanroom construction methodologies (ISO 14644).

What is MPPS for HEPA Filters?

IEST HEPA Filter Type A - Type K

IEST-RP-CC001 designates 11 different HEPA filter categories. Filter types A - E represent HEPA filters measured via MIL-STD-282 standards. The most efficient HEPA filter types, Type J - Type K, are measured by IEST penetration test standards.

Where Can I Buy IEST HEPA Filters Online?

Terra HEPA fan filter units feature Type F HEPA filter ratings as characterized in IEST-RP-CC001.

Type F HEPA filters reflect Stringent IEST standards with capture efficiency (> 99.9995%), as well as filtration efficacy of smaller and more specific particle sizes (0.1 - 0.3 micron).

Chart: IEST vs EN HEPA Filter Testing Methods Compared

The key differences between IEST and EN HEPA Filter testing standards are described as follows:

Test Standards Between America And Europe

Single vs Combined Testing

Two independent tests

Tested using scanning method of leakage test, so the efficiency test and leakage test can be one test

HEPA Definition

IEST-RP-CC001.4 filters are called HEPA filters if NMD 0.3μm thermal DOP efficiency≥99.97% (in total 14 types)

EN 1822 filters are called HEPA filters if MPPS efficiency ≥ 85% (in total 7 types)

Test Procedures

IEST-RP-CC034 introduces two different scanning methods. Additionally, aerosol photometer total leakage test described for special leakage testing when filter access is difficult.

Filter medium test, filter leakage test and filter overall efficiency test

Particle Detection Method

Photometer scanning method (for filters with penetration lager than 0.001%) and particle counter scanning method (for filters with penetration smaller than 0.001%)

Static measuring method or scan method are used to test the overall efficiency, of which the static measuring method use stationary sampling probes to test the concentration of upstream and downstream, and the scan method uses a scanning probe on the downstream side together with a stationary sampling probe set upstream to get the local MPPS efficiency and then the overall efficiency

Testing Filters with efficiency≥ 99.95%

Tested using number mean diameter (NMD) 0.3μm thermal DOP which is approximately near MPPS

Filters with efficiency≥99.95% in EN 1822 are tested for MPPS efficiency and leakage

Testing Filters with MPPS efficiency ≥ 85%

HEPA filters (in total 7 types), while Filters with NMD 0.3μm thermal DOP efficiency≥99.97%

Filters with MPPS efficiency≥ 85% in EN 1822 are called HEPA filters (in total 7 types)

Test Instruments

IEST allows photometer and particle counters (both OPC and CNC)

EN only accepts particle counters (both OPC and CNC) and Different Mobility Analyzers (DMA).

Test Range

OPC in EN 1822 is 0.1~2μm, which is divided into 6 groups; and for CNC is 0.05~0.8μm, and for DMA is 0.01~0.8μm.

The IEST-RP-CC001.4 test range for OPC is 0.1~0.3μm, while for CNC is also 0.1~0.3μm.

Source: Comparison Of HEPA/ULPA Filter Test Standards Between America And Europe (2007) - Authors: Bin Zhou and Jinming Shen - HVAC and Gas Institute Tongji University, Shanghai, China

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