HVAC Filters and MERV Rating

Every air filter has a minimum efficiency reporting value (MERV rating). This number essentially reveals how effective the air filter is, with lower numbers meaning less effective and higher numbers meaning more effective. This doesnít mean you should automatically choose the highest MERV rating you can find, though. As a general rule, most residential air conditioners are designed to work with air filters that have a MERV rating between 7 and 12. These filters are pleated and can trap dust, pollen, and pet dander. Air filters with MERV ratings from 13 to 16 are incredibly effective at removing contaminants from the air, but their small pores can restrict air flow to such a degree that most air conditioners canít force air through them. Choosing a MERV rating thatís too high can significantly reduce your air conditionerís efficiency and may even lead to a breakdown. When in doubt, check your air conditioner to determine the right MERV rating, or ask HVAC maintenance professional. Depending on the type and density of the filter media, different filters can reduce or remove:

Dust: This is the most basic contaminant that air filters seek to remove. Even the least powerful air filter will prevent a substantial amount of dust from entering your HVAC system and circulating throughout your home. (usually MERV 1-4).

Pollen, dust mites, and mold: Allergy sufferers should look for filters that trap these contaminants (usually MERV 5-8).

VOCs (volatile organic compounds): If youíre sensitive to strong odors from cleaning products, household items, or anything that off-gases into your home, look for filters that specifically remove odors and VOCs. Many will include a carbon layer to capture the odors (usually MERV 8-16).

Bacteria: Now weíre getting into hospital-grade filtration. Some people need filters that can remove bacteria due to high sensitivity or because they have a chronic illness (usually MERV 13-17).

Viruses: HEPA filters can usually remove viruses and other tiny particulates that slip by the media in other filters (usually MERV 15-20).

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