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  • What is MERV?

    Minimum Efficiency Reporting Value is a reporting of the effectiveness of air filters in removing particle contaminants from the air and is dependent upon the particle size. MERV was designed by ASHRAE, American Society of Heating, Refrigerating and Air Conditioning Engineers. Generally speaking, a higher MERV rating indicates better filter performance. These ratings are determined by adding particles of varying sizes, from .3 microns to 10 microns, into a controlled testing environment; via independent laboratory. The particles are added upstream of the test filter and a laser particle counter samples the air before it enters the filter and again after it leaves the filter. The two particle counts are compared to calculate the Particle Size Efficiency of the tested filter. Once this is determined, a MERV Parameters chart is used to determine the filters MERV rating. MERV ratings range from 1 – 16 and measurements are in microns. Some of the common particles related to MERV ratings are pet dander, insecticide dust, smog, dust, viruses, wood, tobacco smoke, spores, bacteria and pollen.

  • What is the 9600, 9100, 8500, 8000, or 7500 rating on the DuPont branded products?

    This rating number represents the % of larger airborne particles that are captured when using these filters. Example our Advanced Allergen 8500, removes 85% of larger particles; particles 4 microns or greater.

  • What is Antimicrobial Product Protection?

    Microscopic airborne organisms are often trapped in high performance filters. Left untreated they could multiply on unprotected surfaces. The presence of Microban antimicrobial product protection in the filter material is specifically designed to help reduce the uncontrolled growth of odor causing microbes on the surface of the filter. The anti-microbial in our filters has not been tested for microorganism reduction.

  • What is FPR?

    Home Depot created an Air Filter rating system called Filter Performance Rating (FPR)

    For more information please visit:

  • What is MPR?

    Using particle data between 0.3 and 1 microns in size, the Microparticle Performance Rating (MPR) is 3M's way of demonstrating their filter's superiority at capturing the smallest microscopic particles. A higher MPR rating indicates a more effective 3M Filtrete filter.

  • What is the size of a Micron?
  • What is pressure drop?

    Pressure drop is defined as the difference in pressure between two points of a fluid carrying network. Pressure drop occurs when frictional forces, caused by the resistance to flow, act on a fluid as it flows through the tube.

  • What is arrestance?

    Arrestance is the ability, of an air filtration device, to remove synthetic dust from the air. The arrestance describes how well an air filter removes larger particles such as dirt, lint, hair, and dust. ASHRAE arrestance is a measure of the ability of a device to remove ASHRAE dust from test air.

  • What is dust spot efficiency?

    Filter efficiency is the ratio of particles trapped by a filter over the total number of particles found in the air upstream of the filter. A count of the downstream particles is often used to determine the number of particles trapped by the filter. Filter efficiency can either be based on specific particle size ranges or based on the total number of particles of all sizes. There are numerous testing procedures utilized for determining filter efficiency.

    (Particles Upstream - Particles Downstream) / Particles Upstream = Filter Efficiency

  • How to select an Air Filter?

    Pay close attention to the MERV number, which you will find prominently displayed on all our filters. It tells you how the filter rates, according to ASHRAE, an independent, unbiased organization. A higher MERV indication better filter performance. This allows you to compare filter efficiency. To ensure compatibility with your HVAC unit, please consult your HVAC manual as well.

  • How Often Should I Change My Air Filter?

    How often you should change your filter is determined by multiple factors. Some of the factors are filter type, unit location, environment, extreme weather, foot traffic, and indoor pollutants. This is why you should check your filter every 30 days, as an expired filter may restrict air flow which can impact efficiency of your system and/or damage the systems air handler.

    Depending on the above factors 1” and 2” Pleated HVAC filters can last up to 90 days, but should be check frequently to ensure air flow restriction is not a factor.

    This is Fiberglass filtration products are only rated for 30 days.

    Filters designed to fit into Residential Air Cleaner housings, 3” or thicker have a life span that can range from 6 month to 1 year due to the additional surface area.

  • How do I install my HVAC filter?

    1) Always turn off system or fan before replacing the filter

    2) Carefully remove plastic and/or label from new filter

    3) Be sure the air flow arrow (when present*) on the filter matches the direction of the air flow** (towards the system). **Air is being pulled from your cold air returns, through the filter and then into the unit to be conditioned.

    4) Record installation date

    Additional information on installation:

    Fiberglass no metal filters can be installed either direction, the testing remains the same. This is why we no longer apply an arrow to no metal fiberglass filters.

    Our one metal fiberglass filter should be inserted into the plenum with the metal grid closest to the motor of the unit, so the arrow is pointing toward the blower motor

    Our pleated filters should be inserted into the plenum with the arrow pointing toward the blower motor. If it has metal filter material the metal should be closest to the furnace.

    In regards to our washable filters, you always want to ensure there is a plastic grid between the filter pad and the motor of the unit.

  • Why doesn’t this filter have an air flow arrow?

    Fiberglass no metal filters can be installed either direction, the testing remains the same. This is why we no longer apply an arrow to fiberglass filters.

  • How do I clean this washable filter and how often?

    Washable filters should be cleaned monthly to achieve best results. Cleaning will avoid clogging the filter which could cause equipment malfunction.

    1) To clean, rinse with a hose, sink sprayer or shower head with cold to lukewarm water (do not use HOT water). For heavy dirt build up, soak filter in a very mild solution of laundry soap and water. Then rinse thoroughly with clean water

    2) Shake out any excess water.

    3) Allow the filter to fully dry. Do not place in sun.

    4) Reinstall the filter

  • Is there a warranty on your filters?

    Any filter found to be defective in workmanship or materials, within one year of the purchase date, will be repaired or replaced upon proof of purchase and prepaid return to the factory. This warranty will be invalid if the proper use and maintenance instructions were not followed.

  • Are your Filters UV compatible?

    No, Protect Plus does not currently offer filtrations products that are compatible with UV light systems.

Still have questions?

[email protected]

Air Filtration: 888-808-9100

Protect Plus

PO Box 9181

Hickory, NC 28603 – USA