Unveiling the Mysteries: HEPA vs. MERV – A Deep Dive into Air Filtration Standards
While choosing an air purifier, we find that some are HEPA grade and some are MERV grade. So what is the difference, and how should I choose? Now, let's talk about the difference between HEPA and MERV standards. HEPA (High Efficiency Particulate Air) and MERV (Minimum Efficiency Reporting Value) are two different efficiency standards for filters, mainly used to describe the ability of filters to capture particulate matter in the air.
HEPA standard
The US Department of Energy (DOE) initially established the HEPA standard, which defines a filter capable of capturing at least 99.97% of particles with a diameter of 0.3 micrometres in the air.
HEPA filters are typically classified into the following grades:
H11 to H14: This is the HEPA level defined in the European standard EN 1822, with H14 being one of the most efficient levels, capable of capturing particles up to 0.12 microns with an efficiency of up to 99.995%.
U15 to U16: These are grades of Ultra HEPA filters, capable of capturing particles up to 0.12 microns with an efficiency of 99.9995%.
HEPA filters are mainly used in environments requiring extra high cleanliness, such as hospital operating rooms, laboratories, electronic manufacturing industries, etc.
MERV standard
The American Society of Heating, Ventilation, and Air Conditioning Engineers (ASHRAE) developed the MERV standard to evaluate the efficiency of filters. The MERV rating range is from 1 to 20, with more significant numbers indicating higher efficiency of the filter. The MERV standard considers the capture efficiency of particles of different sizes and evaluates the average efficiency of filters at different particle sizes.
The approximate range of MERV levels is as follows:
MERV 1 to 4: mainly captures large particles such as dust and pollen.
MERV 5 to 8: Provides basic filtering capabilities, suitable for ordinary residential and some commercial buildings.
MERV 9 to 12: This filter provides good filtration performance, can capture smaller particles, and is suitable for most residential and commercial applications.
MERV 13 to 16: Provides highly efficient filtration capabilities, capable of capturing small particles such as bacteria and viruses, suitable for environments with high air quality requirements.
MERV 17 to 20: These grades typically approach the performance of HEPA filters and are suitable for special applications such as biosafety laboratories.
The difference between HEPA and MERV
Filtration efficiency: HEPA filters have an explicit requirement of 99.97% filtration efficiency, while MERV filters have a more comprehensive efficiency range. The performance of HEPA13 is similar to that of MERV17.
Standard-setting agencies: HEPA standards are developed by DOE, while ASHRAE develops MERV standards.
Application areas: Nowadays, HVAC systems generally use MERV standards, while air purifiers tend to use HEPA standards.
Conclusion
Now that you understand their differences, you can compare the parameters more clearly when choosing air purifiers.
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