Air Purifier Standards Around the World: HEPA Grades, CADR, and CCM

The short answer

Air purifiers are rated differently in North America, Europe, and China, so numbers on the box are not always comparable. The three things worth knowing are how HEPA is graded, which standard a CADR figure came from, and whether a filter's long-term capacity is rated at all. Research from Canada, Australia, and Southeast Asia has reached similar conclusions about smoke: purifiers reduce indoor fine particles, with a wide range of results.

HEPA grades: US vs. Europe

In the US, a True HEPA filter must capture at least 99.97% of 0.3-micron particles. In Europe, filters are classified under EN 1822, which has been largely carried into the international standard ISO 29463. These test each filter at its most penetrating particle size (MPPS) rather than at a fixed 0.3 microns.

At the H13 level, the US and European approaches are broadly comparable, though the test methods differ. Seeing H13 on a label is good, but only if it names the standard. Labels that say H13 or medical grade without citing EN 1822 or ISO 29463 are unverified claims.

CADR: three systems, one idea

• North America: CADR measured under the AHAM standard, reported in cubic feet per minute (CFM), with separate smoke, dust, and pollen numbers. Our sizing guide uses the smoke figure.
• Europe and elsewhere: CADR is often quoted in cubic meters per hour (m3/h). One CFM is about 1.7 m3/h, so a 200 CFM purifier is roughly 340 m3/h. Convert before comparing.
• China: The national standard GB/T 18801 (introduced in its current form in 2015 and revised since) measures CADR but also adds CCM, cumulative clean mass, which indicates how much pollutant a purifier can remove before its performance falls to a set fraction of the original. It also covers gas pollutants such as formaldehyde, energy efficiency, and noise. Particle CCM is graded P1 to P4 and formaldehyde CCM F1 to F4.

CADR tells you how fast a new purifier cleans the air. CCM tells you how long that performance lasts. A model can have a high CADR and a short filter life, which is why a CCM grade is worth looking for on products that report one.

Health guidelines used in the research

The NCCEH review of smoke studies compared indoor results to two benchmarks: Canada's 24-hour ambient air quality standard for PM2.5 of 27 micrograms per cubic meter, and the World Health Organization's 2021 guideline of 15 micrograms per cubic meter over 24 hours.

Research from outside the US

• Canada. The National Collaborating Centre for Environmental Health reviewed 30 studies on air filtration during smoke episodes and found it may reduce indoor PM2.5, with low certainty about the size of the effect. Health Canada also publishes guidance on choosing a portable air purifier.
• Australia. A 2024 study by Wheeler and colleagues put HEPA cleaners in 10 semirural homes in Victoria during prescribed burning. Indoor PM2.5 fell by 30 to 74%, depending on the house. A 2021 study of a public library in Port Macquarie, New South Wales, during bushfire and peat fire smoke concluded that appropriately sized HEPA cleaners can improve air in a public shelter further.
• Southeast Asia. Several studies examined the 2013 and 2015 regional haze episodes, including work in air-conditioned buildings in Singapore and a classroom fan-filter study. They are the main non-North American evidence on filtration during smoke and haze, though the review notes most studies were small.

What this means when you shop

1. Compare smoke CADR in the same units (CFM or m3/h).
2. Ask which standard the HEPA claim follows (True HEPA, or EN 1822 / ISO 29463 class).
3. If a brand sells in China, look for its GB/T 18801 CCM grade as a sign of filter capacity.
4. Treat unsourced percentage claims as marketing.

Sources

• NCCEH and NCCMT. Indoor air filtration during wildfires: Impacts on air quality and health (2025). ncceh.ca
• Health Canada. Choosing a portable air purifier. canada.ca
• Wheeler AJ, et al. Evaluating portable air cleaner effectiveness in residential settings to reduce exposures to biomass smoke resulting from prescribed burns. Public Health Research & Practice 34(1) (2024). doi.org/10.17061/phrp33232307
• Wheeler AJ, et al. Can public spaces effectively be used as cleaner indoor air shelters during extreme smoke events? Int J Environ Res Public Health 18(8):4085 (2021). doi.org/10.3390/ijerph18084085
• EN 1822-1:2019 and ISO 29463 (HEPA and ULPA classification).
• GB/T 18801 (China national standard for air cleaners).
• Southeast Asian haze studies listed in the NCCEH review (Chen et al. 2016; Sharma and Balasubramanian 2017; Tham et al. 2021).