MERV Rating - Understanding Your Furnace Filter’s Most Important Number

When shopping for furnace filters you may find yourself asking this peculiar question – “What’s a MERV?”

It’s not the name of a long-lost eccentric uncle or a talk show host you see on the retro TV station. It stands for "Minimum Efficiency Reporting Value."

A MERV rating is used to rate the ability of home furnace filters to remove airborne particles from the air as it passes through the filter. It is a standard used to measure the overall efficiency of a furnace filter and measures a filter's ability to remove particles from .30 to 10 microns in size.  To give you an idea of the size of a micron, 100 microns is about the thickness of a piece of paper or a human hair.

The higher MERV rating the better performing a furnace filter us at the cleaning dirt, dust and grime particles from your air. The MERV rating needed for your furnace system comes down to your sensitivity to dust and other pollutants and air quality issues you face in your home.

A quality 8 MERV furnace filter will handle many of the larger air-borne particles that are common in most homes. However, if you or a loved one has respiratory issues it may be better to go with a 13 MERV filter. It is all based on personal preference and the conditions you face.

Here are examples of MERV ratings and the particles they filter:

• A MERV rating of 13 means the filter is 89-90% minimum efficient at capturing measured particles such as bacteria, tobacco smoke and particles that make you sneeze.

• A MERV rating of 11 means the filter is 80-85% minimum efficient at capturing measured particles such as humidifier dust, lead dust, milled flour, auto emissions and other fumes.

• A MERV rating of 8 means the filter is 60% minimum efficient at capturing measured particles such as mold spores, hair spray, fabric protector, dusting aids, cement dust and pet dander.

• Typical fiberglass throw-away filters are rated at a 4 MERV and below with a 6% minimum efficient at capturing the measured particles like pollen, sanding dust and large dust particles.

Which furnace filter MERV rating should you select for your home? No one can give you the definitive answer to which is best for your situation...not a scientist, engineer or HVAC contractor...it's your health we're talking about and your choice.

At Furnace Filters Made Easy, we suggest with a MERV rating of 8 or higher because your family's health is of critical importance. Avoid the cheap $2 fiberglass furnace filters found in hardware stores. They only capture large particles and allow respiratory irritants to continue circulating through your home.

You can find a helpful MERV ratings chart by visiting www.furnace-filters-made-easy.com.