Do air filters really work? Research has shown that filtering the air can help remove hazardous particles from indoor spaces, particularly allergens, smoke, and mold. However, air purifiers are most effective when used in combination with proper filtration and home cleaning techniques. Bipolar ionization (also known as needle point bipolar ionization) is a technology that can be used in HVAC systems or portable air cleaners to generate positively and negatively charged particles. The Environmental Protection Agency (EPA) has warned that air purifiers are limited in terms of filtering gases and that filters must be replaced regularly for optimal performance, usually every three months. It takes time for all the air in the room to pass through the purifier, so odors can linger for about an hour.
This means that in addition to the purchase price of an air purifier, you should also consider operating costs and filter replacement costs. Additionally, other factors in your home can affect its effectiveness, such as ventilation (open or closed windows) and new particles that are constantly emerging, so the air may not be as filtered as claimed. For more information on air cleaning and filtration and other important engineering controls, please refer to ASHRAE and the CDC. Note that there are many air cleaning devices that do not use bipolar ionization; device packaging or merchandising materials will generally indicate if bipolar ionization technology is being used. When used correctly, air and HVAC filters can help reduce airborne contaminants, including viruses, in a small building or space.
In fact, air purifiers can neutralize some of the threat posed by air pollution and indoor activities. Where to place a portable air purifier in your home to help protect yourself from airborne infections depends on the situation. The performance of different DIY air purifiers will vary and cannot be reliably evaluated without specialized instruments. If you notice an improvement at first only to have it decrease later, remember to check the filter to see if it needs to be changed. Reusable filters are generally good at removing larger particles from the air, such as dust mites and pollen.
The quality of the carbon filter will determine its effectiveness in trapping smoke, VOCs, and odors. For an air purifier to be effective in removing viruses from the air, it must be capable of removing small particles in the air (in the 0.1-1um size range). Some air purifiers use ionizers to help attract particles such as static negative ions that bind to dust and allergens and cause them to be deposited out of the air.