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Air Quality Terms

Clean Air Terms

  • EER

    SEER is related to the Energy Efficiency Ratio (EER) and also to the coefficient of performance (COP) commonly used in thermodynamics. COP is a measure of efficiency. The COP of a heat pump is determined by dividing the energy output of the heat pump by the electrical energy needed to run the heat pump.

  • What is OEM?

    The acronym OEM stands for Original Equipment Manufacturer. This means that the product was manufactured by the original company that produced the product. For instance. If you have a Holmes air cleaner you would purchase a replacement filter that was manufactured by Holmes for Holmes air cleaner products. Other companies make replacement filters however, many of the generic knock-off's or fake brand name filters may be of inferior quality in order to get the price down. It may be in old cliche but you do usually get what you pay for. FiltersUSA provides genuine OEM products together with some generic products that meet or exceed the manufacturers specifications. Preserve your warranty and look for OEM products.

  • MERV

    The MERV System (Minimum Efficiency Reporting Value) was instituted to provide minimum efficiency values. When you first install your new filter, its efficiency is at its lowest point. That's because it hasn't built up enough dust and particles on the filter to help trap more dust and particles.

    The MERV Rating will give you a worst-case scenario for the lowest amount of efficiency you can expect from your filter. This MERV System also measures the size of the particles a filter can trap. The scale that the MERV System uses can range from a MERV 1 to a MERV 16 (95%+ ASHRAE filter). The MERV System is an excellent tool when you know which contaminants you want to have filtered.


    American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is an international membership organization founded to advance the arts and sciences of heating, ventilation, air conditioning, refrigeration and related issues. This site contains information, guidelines and standards to assist HVAC&R practitioners, and resources for ASHRAE members.
  • What is CADR
    Clean Air Delivery rate

    The AHAM seal (usually found on the back of an air cleaner's box) will list three CADR numbers - one for tobacco smoke, one for pollen and one for dust. The CADR indicates volume of filtered air delivered by an air cleaner. The higher the tobacco smoke, pollen and dust numbers, the faster the unit filters the air. When a manufacture obtains product approval for meeting government standards and UL approval, what they state as being 99.97% efficient, has their OEM filter installed. If you would use a generic filter instead, you might get 75% efficiently or using another brand might burn the motor out, not allowing enough air to pass thru the filter. It is always important to look for genuine OEM replacement filters to maintain the efficiency of your air cleaner.

    Follow our 2/3 Rule:
    You'll always want a unit with a tobacco smoke CADR at least 2/3 your room's area. For example, a 10' x 12' room -120 square feet - would require an air cleaner with a tobacco smoke CADR of at least 80. If your room size is smaller, the unit will simply clean the air more often or faster. If you have ceilings higher than 8', you'll want an air cleaner rated for a larger room.

  • Condenser Coil

    The air conditioner or heat pump condenser coil is located outside of your home. Be sure to check that leaves and debris have not clogged the coil fins.The condenser coil is one of the highest energy consuming components of an air conditioning system. Thus, selecting a highly efficient central air conditioner often requires that the model have an efficient model of condenser coil.

    You probably do not need to worry about the particular model of condenser coil when you purchase a central air conditioner -- instead, pay attention to the efficiency measures such as SEER and EER.

  • Evaporator Coil (A-coil)

    The air conditioner evaporator coil is located inside your furnace or air mover. This picture depicts a coil which had the air filter missing from the furnace. Instead of dust being collected by the furnace filter, here it collected on coil causing strain on the air mover and a strain on your pocketbook. When you inspect the coil, be sure to turn the circuit breaker off to your furnace. This situation will cost you more in daily operation, will cost your more to clean the coil, and may cost you more with premature failure of your blower motor. Changing your filter could prevent this situation from happening in the first place.

  • HEPA

    The Letters in the word HEPA stand for High Efficiency Particulate Arrestance.

    The HEPA filter was developed during World War II by the Atomic Energy Commission and it was designed to remove and capture radioactive dust particles from the air which might escape and present a health hazard to the researchers. The HEPA filter was specifically designed to protect the Human Respiratory System.

    For a filter to be labeled "True" HEPA, it must be certified 99.97% efficient in capturing 0.3 micron (not 0.1 or 0.01 etc..) respirable-size-particles (RSP) according to the U.S. Military Standard MIL-STD-282, commonly known as the DOP test. The reason 0.3 micron is used and no other is because 0.3 micron is the size at which all mechanical filters are LEAST efficient in capturing. Other methods of testing do not give a true picture of efficiencies relative to respirable-size-particle (RSP) capture.

  • HVAC

    The acronym HVAC commonly refers to Heating, Ventilating and Air Conditioning. Some parts of the country may only have air conditioning while other parts of the country may have furnaces with or without air conditioning. This term is can be applied to air comfort systems for all situations.

  • Micron -A micron is a measure of length: "1 micron equals 1 millionth of a meter". A particle that is 10 microns or less in size is not visible to the naked human eye.
    Examples of some common air contaminants and their size in microns:
    • Human Hair (70 - 100 microns)
    • Pet Dander  (0.5 - 100 microns)
    • Pollen  (5 - 100 microns)
    • Spores from Plants (6 - 100 microns)
    • Mold (2 - 20 microns)
    • Smoke (.01 - 1 micron)
    • Dust Mite Debris (0.5 - 50 microns)
    • Household Dust (.05 - 100 microns)
    • Skin Flakes (0.4 - 10 microns)
    • Bacteria (0.35 - 10 microns)

  • IAQ

    Indoor Air Quality. Improving the quality of your indoor air can be as simple as changing your filters on a regular basis or using portable or central air cleaners or purifiers. A John Hopkins University study suggests indoor air pollution increases asthma symtoms. You can learn more about indoor air pollution from the CDC Indoor Air Quality page.

  • SEER

    The efficiency of air conditioners are often rated by the Seasonal Energy Efficiency Ratio (SEER). The higher the SEER rating of a unit, the more energy efficient it is.