HEPA VS MERV
Freepik

HEPA vs MERV: The Furnace Filter Battle

Whether you are looking for a furnace filter or a HEPA filter, the word MERV will pop out. Most people tend to lean towards a higher number without knowing why. Today at airfuji, we are going to end the confusion and explore everything about MERV. Starting with what is the ratings for? How should I use it? What are the best ratings for home use? Should I get HEPA filter or MERV filter for my furnace? All your questions shall be answered below.

Short answer

Choose at least MERV 9 filter.

Long answer

Filter media is made up of many fiberglass threads compressed in unsystematic directions. The purification begins when a force of airflow pulls the particles towards the filter. The filter's fiberglass would then intercept the particles from proceeding. This leaves only filtered air exhausted into the air and the cleaning cycle will start again.

What is HEPA Filter MERV Rating?

Acronym for High-efficiency Particulate Air. HEPA filter is ranked between 17-20 MERV; the highest group in MERV ratings. All HEPA filters are tested and certified to be at least 99.97% efficiency in removing particles as small as 0.3 microns. Use in all hospital as it can trap even the tiniest airborne irritants and keeping them in bay. This includes bacteria and viruses that are highly contagious in indoor airspace.

What is MERV rating?

Acronym or Minimum Efficiency Reporting Value, MERV filters are rated based on how small airborne particles can be removed. The rating scale range from 1 to 16, above 16 would be categorized as a True HEPA filter. A low-quality filter is rated between 1-4 MERV and medium filter is rated between 5-12 MERV range. Filter in this range can remove dust, hair, dust mites, mold and pollen. High-efficiency/ HEPA-based filter (NOT True HEPA) is rated from 13-16 MERV. The filter in this group can further target finer dust, bacteria, and smaller mold/ pollen.

What MERV Rating Should I Use

All air filter can remove dust and hair. For home or hospital, you should go with at least MERV 9 filter and above. It has at least 85% efficiency against finer particles like dust mite, pet dander, mold, pollen, and spore. All these contaminants can be found regularly roaming in a household. If you are not hypersensitive to dust or other allergens, you could stay at the lower end number. If you have asthma, children or suffering from respiratory illnesses, consider MERV 13 filter and above. It is effective in removing germs and other microorganisms from spreading.

Our recommended MERV rating for furnace filter is between 9-16. Beyond 16 would be at HEPA filter territory and not all HVAC system support that.

Ratings0.3-1 microns1-3 microns3-10 micronsFilter TypeControlled Particles
MERV 1<20%Pre-filter/ Aluminum MeshDust, dust mites, pet dander, pollen
MERV 2<20%
MERV 3<20%
MERV 4<20%
MERV 520-34%Low Quality MERV FilterMold, spores, cooking dust, hair spray
MERV 635-49%
MERV 750-69%
MERV 8<20%<70%
MERV 9<35%<35%Standard MERV Filterlead dust, smaller mold, smaller pollen
MERV 1050-64%<75%
MERV 11<20%65-79%<80%
MERV 12<35%80%<85%
MERV 13<50%<90%<90%Superior MERV FilterBacteria, viruses, fine dust
MERV 1475-84%<90%<90%
MERV 1585-94%<90%<90%
MERV 16<95%<95%<95%
MERV 1799.97%<99%<99%HEPA/ ULPA FilterSmall bacteria and viruses, fumes
MERV 1899.997%<99%<99%
MERV 1999.9997%<99%<99%
MERV 2099.99997%<99%<99%

Is Higher MERV Rating Better?

For air purifier YES, as it can filter finer particles and microbes. For HVAC system not necessarily. MERV ratings are separated into 5 groups based on the particles size it can capture. The higher the MERV rating, the higher the filter’s density it will be. This creates a stronger resistance to the airflow as less air would be able to bypass the filter. Without enough air pulling in the particles, the air circulation would be inefficient and stagnant. In worst-case scenario, it can even damage your HVAC system due to the increased pressure on the fan.

Find out more info about your furnace or HVAC system before installing a MERV filter. If you are still unsure, hire an HVAC professional to do the checking for you.

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