What Type of Air Filter is Best for Covid-19 Prevention?

Ventilation is essential for maintaining good air quality indoors, and given the amount of time people spend inside, it is important to understand the best ways to bring in fresh air. The simplest way to do this is by opening windows, but this isn't always the most energy efficient option. To maximize the impact, the Centers for Disease Control and Prevention (CDC) suggests placing a fan “as close as possible to an open window, which blows out.” This creates a kind of homemade exhaust fan, instead of forcing polluted air to stay inside. Additionally, turning on bathroom exhaust fans can help bring in more outside air.

When it comes to air filtration, the CDC recommends using filters with MERV-13 ratings or higher, as these can trap smaller particles, including viruses. HEPA (high-efficiency particulate air) filters are particularly effective at capturing more than 99% of airborne particles that contain the COVID-19 virus. If you are looking for an air purifier for your home, it is important to consider the size of the room and the height of the ceilings. The square footage rating on a product description is calculated using the purifier's clean air supply rate (CADR), but this assumes 8-foot ceilings.

If your room has higher ceilings, you may need to increase the size of your purifier. When using an air purifier, it is important to make sure that it circulates clean air around the space. The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) suggests placing your air purifier in a place where “its air inlet is not obstructed by furniture and its outlet can move air as far as possible before diverting or dragging it to a return or exhaust grill, such as a bathroom or kitchen fan.” Additionally, if you don't plan to run your air purifier at its highest setting, Bahnfleth recommends increasing the size. Ventilation and air filtration cannot replace other precautions such as wearing masks. In fact, a study published in The Journal of Infectious Diseases found that combining a tested N95 with an efficient HEPA air purifier in a simulated healthcare environment could almost completely eliminate the risk of infection.

Combining masking with HEPA filtration is also more likely to prevent infection than either measure alone. When it comes to selecting an air purifier for your home, there are several options available. The Coway air purifier is ideal for rooms up to 361 square feet and has a four-stage filter that includes HEPA filtration of up to 99.9% of superfine particles such as viruses, bacteria, mold and more. Another option for small and medium-sized rooms is the Levoit Core 300, ozone-free, which has a three-stage filtration system with a HEPA filter that captures 99.97% of 0.3 micron particles. In addition to purchasing an air purifier for your home, you may also want to consider upgrading the HVAC filters in your building or installing an in-line modernization system. An in-line modernization system uses HEPA filtration and directional airflow to move filtered air from an elevated supply through the occupant breathing area and down to a return air intake at ground level.

Reusable filters can also be used to collect large particles before they reach the primary filter. It is important to remember that an air purifier can't work efficiently if it has a dirty filter. You should generally replace filters (or clean those that can be vacuumed) every six to 12 months for pleated filters and every three months for activated carbon filters.