Can Your Furnace Air Filters Help Fight Coronavirus (COVID-19)?

Posted by Barry Kindt on

It’s become quite a cliche statement, but we really are experiencing “unprecedented times,” nearly ONE YEAR later. To help stop the spread of COVID-19, it’s important to take safety precautions in many aspects of our lives. These measures include your use of “central” furnace and air conditioning filters in your home and/or office.

The Basics of Air Filters

The filter’s primary function is to protect the operation of the equipment, not the occupants of homes or businesses! Sounds outrageous, doesn’t it?

We call the typical 1-inch thick filter you’ll find at “box” stores “boulder catchers”; certainly NOT appropriate to catch and hold dust, bacteria or airborne viruses. So, changing your dirty standard air filter with a “boulder catcher” does nothing to protect the health of the occupants. If you can see through the filter, it can’t capture particles you can’t see! Fine dust, molds, viruses and bacteria are NOT visible to the human eye.

What’s a Homeowner or Business Owner to Do?

In one word—upgrade!

If you already have upgraded filters, follow the recommended replacement schedule and modify based on your environment. Living near a busy highway, living with wall to wall carpet, highly active children, pets, and wooded areas will increase the replacement frequency. (Carpeting is a dust and dirt catcher—walk across the carpet and you stir up a fine cloud of dust and particles behind you that you don’t see. When is the last time you saw the obnoxious cologne your friend was wearing?)

Most standard “central” system filters are rated with a MERV (Minimum Efficiency Reporting Value) rating, which designates the size of the particle the filter media will catch and hold. The higher the MERV rating, the more restrictive air flow and particulate flow back into the air we breathe. Studies show that using a MERV 13-rated filter works at a 95% efficiency level in capturing the COVID-19 virus particle. This filter will hold the virus particle long enough to render it harmless.

Ductless filters are rarely rated in MERV. The large ductless filters are supposed to be cleaned every 2 to 3 weeks and replaced annually or bi-annually. Most ductless units have specialty air filters available to help capture the fine particles, remove odors or add “health-enhancing” products to the air.

The challenge with “central” systems becomes the restriction to airflow, which can cause significant system efficiency loss, higher operating costs, and damage to marginally healthy equipment! In fact, many air duct systems are undersized, making the use of higher efficiency filtration even more dangerous to equipment longevity, cost-efficient operation, and healthy living.

HEPA Air Filters

The word ‘HEPA’ stands for High-Efficiency Particulate Air. This type of air filter can trap up to 99.97 percent of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns, the most penetrable size of air particles. Their MERV ratings (Minimum Efficiency Reporting Values) are among the highest of air filter types. To see a table of ratings and their respective particle size blockage, see the EPA’s table here.

Structurally, these filters have an interlaced glass fiber construction twisted together to make a sustainable fibrous maze. So when particles move through the web, the filters pick them out of circulation.

Despite the standards and certifications being as recent as 1983, HEPA air filters actually date back to World War II. American scientists with the Manhattan Project created the first HEPA air purifiers to capture radioactive particles that atomic bombs released. 

How HEPA Air Filters Help Cleanse the Air of COVID-19

When people carrying the coronavirus talk, sing, cough, yell or even breathe, they release the virus into the air through particles ranging in various sizes. Although the large respiratory droplets fall quickly, the smaller aerosols are able to remain in the air for 30 minutes or longer until they’re taken away through ventilation or captured by an air-purification system.

Air cleaning filters specifically filter out all kinds of dust, pollen, mold, bacteria, and airborne particles; reducing airborne contaminants including viruses. Air purifiers are also helpful when you have limited ventilation from the outdoors. 

To help reduce the amount of viral contaminants from the air, it’s best to use HEPA air filters that come with MERV ratings ranging from 0.1 to 1 micron capture, and make sure to be on top of checking them and changing them for new filters on their proper frequency and recommended schedule. 

Air Cleaners in Your Home

A central heating and cooling system can be the ideal way to decrease indoor air pollutants as it regularly exchanges the air throughout each room of a home. Keep in mind, your standard air filter is made to protect your unit, so you can’t exactly count on them to remove the virus.

A Central Air Purifier (CAP) Could Be a Better Answer

Using a “bypass” type HEPA air purification unit attached to your present system will help avoid the airflow restrictions caused by simply replacing an existing flow-through furnace filter. The “bypass” CAP unit uses a percentage of the system’s airflow, cleaning it systematically and in concert with an upgraded, but not too restrictive air filter. 


The CAP is a multi-layered filtration unit with the first layer of filters removing the large particles, and the HEPA core removing the smaller particles. This layering helps increase the longevity of the HEPA core, which could last 2 to 3 years. The system circulates air continuously, even when the furnace or air conditioning unit is operating and eventually, all the air in the home is cleaned.

Cleaner Air in Commercial Buildings

Much like your home air conditioning system, a commercial HVAC system filters the air before allowing it to move into areas around the building. Upgrading the filter is a bit easier because most systems are built with filter racks that enable the owner to upgrade to thicker and higher efficiency filters. 

One key difference between home systems and commercial systems is a requirement for commercial buildings to introduce outdoor air into the system, mostly to fight the ill effects of the carbon dioxide produced by various sources, including humans. Yes, it pulls in the hot and humid air in the summer, cold air in the winter, and whatever is in the outside air making filter changes and maintenance ever more important; all while increasing energy consumption! 

We’ll talk about an answer next time…

Can we help with your filter needs? Contact us today!