How to Choose the Right Air Filter

FREMONT — When purchasing an air filter for your HVAC system, you have a lot of options to choose from. One important thing to know about is the Minimum Efficiency Reporting Value (MERV) rating scale, which is used to assess filter effectiveness.

With MERV, filters are rated on a scale of 1 to 20, with 1 being the least effective and 20 being the most effective. For example, a MERV 3 filter can capture 70 to 75 percent of basic airborne particles like pollen, dust mites and pet dander, whereas a MERV 8 filter can capture more than 90 percent. Filters rated MERV 9 to 11 are also able to capture mold spores, smog and odors, and those rated MERV 13 to 16 add smoke, bacteria and allergens to the target list. At the top of the spectrum are MERV 20 filters, which can filter down to the size of airborne viruses.

While a higher MERV rating means greater effectiveness, it also means a greater expense, which is why you have to weigh cost versus benefits when purchasing one for your home. Keep in mind that anything higher than MERV 16 is excessive in a residential setting, as these are designed for use in highly sensitive industrial or laboratory settings. You should also make sure to get a filter that’s appropriate for your HVAC system, as an overly restrictive filter can inhibit proper airflow, which can cause the system to malfunction.

To ensure a minimum baseline of performance, it’s best to avoid any air filter rated below MERV 5. MERV 9 filters, which are designated as “Better Residential,” are a good choice, but if you’re extra concerned about the quality of your indoor air, consider upgrading to a MERV 13 filter, which is designated as “Superior Residential.”