Can an Air Filter be Too Strong?

Learn about potential risks associated with using high-efficiency HEPA filters in your home's HVAC system and how to avoid them.

Can an Air Filter be Too Strong?

When it comes to high-efficiency filters, such as the HEPA filter, you may be wondering if it is possible to have too much of a good thing. The short answer is that it can, but it's not really a problem except in extreme circumstances. Most modern HVAC systems have no problem working with higher MERV filters, so millions of homeowners rely on them. The main risk of high-efficiency air filters comes from the fact that they are not modified for long periods of time.

If you're aware of changing your filters regularly, you're unlikely to experience any issues with your HVAC system. The effectiveness of a filter is measured as MERV, or Minimum Efficiency Report Value. The higher the MERV, the smaller the particles the filter stops, but also the more resistance to the airflow it creates. Residential air filters must have a MERV rating between 4 and 12, but not higher.

The well-known HEPA filter is usually too strong for domestic use; it is best suited for industrial and sanitary installations. Air conditioners can shut down if fine filters restrict airflow. The air conditioner is also affected by a dirty filter that slows down the air flow, making the system work harder. In addition, your system may not be able to provide enough heating or cooling to the house.

Or just one or two distant rooms become uncomfortable. Furnace filters designed to act as whole-house air filters add stress to the blower of an HVAC system by preventing air flow. Two design adjustments during installation can resolve this issue and potentially prevent an after-hours call from a disgruntled customer. The wire mesh also helps prevent the air filter from collapsing when air circulates through the filter and the HVAC system.

Air filters, which have a coarse medium filter, can trap small particles, such as pet dander and mold, without impeding air flow like a thin, pleated air filter would. One consequence of a very effective air filter is the speed with which it can be loaded with contaminants and begin to increase the pressure drop. You don't want to go wrong and end up with a filter that doesn't stop pollutants in the air or that afflicts the air conditioner. Thin filters with higher MERV ratings can prevent air from flowing through the filter, which changes the air pressure in the ventilation system. Some air conditioning filters with a high MERV rating can lower air pressure in the duct system, which can increase energy bills and damage the HVAC system. If your family has allergic reactions or respiratory problems and you want a powerful MERV air filter, look for a home air filtration solution that can meet your needs and filter desires.

But if the filter were thicker than 2 inches, it would have more surface area to leave more room for air to pass through and not restrict air flow. Unfortunately, the MERV scale measures the ability of a filter to affect indoor air quality, not the efficiency with which it supplies air to the blower, says Eric Weiss, technical trainer at Trane Residential. Each air filter has its own life expectancy, in which its efficiency and performance may decrease over time. Opinions vary widely on this subject, but all professionals agree that a good HVAC air filter is necessary for your home because they have seen all the problems that an incorrect type of air filter can create in a home's HVAC system. If the filter fabric is dense, it will stop smaller and smaller particles; but it will also slow down the air flow of the air conditioner's air handler. It is better to use filters with wide pleats and ensure that the ventilation grilles are free of any material that could block airflow.