No, not all air filters are the same. Depending on the type of unit that you have, its size, and what your health goals are, you want to choose a different type of filter. If you’re unsure of what type of filter to buy, then you want to speak with a certified representative from the manufacturer of your unit to be sure that you are installing the correct type.

MERV Ratings

MERV stands for Minimum Efficiency Reporting Value. The higher the MERV value, the fewer particles can get through your filters,, such as dust and other emissions. People have different needs in their homes, and hospitals certainly have a responsibility to prevent airborne illnesses from traveling and infecting susceptible patients or people undergoing surgery. MERV ratings help to determine which filters are best for different situations. Some ratings and what they block include:

  • MERV rating of 1-2: Textile and carpet fibers.
  • MERV rating 3-4: Dust mites, pollen, and sanding dust
  • MERV rating 5-7: Cement dust, dusting aids, fabric protectors, mold spores and hairspray
  • MERV rating 8-10: Auto emissions and even milled flour
  • MERV rating 11-12: Humidifier dust, Legionella and lead dust

Lastly, High-Efficiency Particulate Air or High-Efficiency Particulate Absorbent, or HEPA filters have the highest number ratings between 17 and 20, which are far higher than you will find in most residential homes.


For filters with a MERV rating between 1 and 2 typically are made out of spun fiberglass fibers, and are generally about an inch thick. These filters do not filter out the most particles, and so they are better for people who do not have allergies or asthma. But don’t think that these won’t improve your health. According to an Illinois Institute of Technology study, using one of these filters can reduce your chances of contracting a respiratory illness, such as influenza or rhinoviruses or coronaviruses, up to almost 30%. That is a significant jump in protection compared to not using a filter at all.

The next type of filter that has a higher MERV rating is a pleated filter. They are typically made out of either cotton or polyester, with cotton as the top choice. These filters are pleated which means that there is more surface area to allow for contaminants to be trapped, and some cotton filters have electrostatic qualities to attract pollutants to them from the air.

Most HEPA filters are made of interlaced glass fibers that are twisted and combined in so many ways that it creates a very tight, irregular barrier or maze that the particles have difficulty passing through. When particles are blocked or cannot be sifted through, then you have a better chance of preventing the contraction of serious illnesses.


As mentioned earlier, different units will require different sizes of filters. You may need 20x30x1 air filters or a different size. You should never cut your air filters. Instead you should buy filters that are properly sized to fit your unit. Filters are specifically designed to fit in the units that are made by the same manufacturer, so if you have a Rheem, American Standard, Trane, or any other major brand’s unit, then you will want to use the filter made specifically by them. That ensures that you are keeping your air clean and allowing for proper airflow in your home.

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