When it comes to using products with technology that can generate ozone, it is essential to make sure that the equipment meets the UL 867 certification (standard for electrostatic air filters) for acceptable levels of ozone production, or even better, the UL 2998 certification (Procedure for Validation of Environmental Declarations (ECVP) for zero ozone emissions from air filters). This is to guarantee that the performance data documented in the terms of use is available from multiple sources, some of which should be independent third-party sources. Any performance claims that are not backed up or limited case studies where there is only one device in a room and no reference controls should be questioned. Using air filters alone cannot guarantee good air quality, especially when there are significant sources of pollutants and ventilation is inadequate. However, these filters have some drawbacks.
To begin with, they usually cost more than basic fiberglass filters. Many manufacturers use the Clean Air Supply Rate Rating (CADR) system to evaluate air filter performance. Both are evidence that smoke-filled air finds a way around the clogged filter and not through it, and that it's time to install a new one. Home air purifiers are indoor air filters that can be assembled with box fans and square HVAC filters (or boilers). The air is charged with particulate matter, passes through the filter only once and the results are measured.
If your air conditioning system uses a thicker filter (typically 4 to 5 inches and is usually mounted on the air controller), it's likely designed specifically for medium-efficiency MERV filtration. If you can't find the Nordic Pure in your size or if you prefer to immediately buy and pick up a new filter at a store, Honeywell FPR 9 filters and Filtrete MPR 1500 filters are similar and are widely available at retail stores. These products generate ions, reactive oxidative species (ROS, which are sold under many names), or chemicals in the air as part of the air cleaning process. Air conditioning systems in large buildings often filter air before it is distributed throughout the building, so consider updating the air conditioning filters as appropriate for your specific building and air conditioning system (consult an HVAC professional). Using a homemade air filter that isn't properly designed or assembled doesn't worsen indoor air quality, and even so, it can offer some benefits.
Compared to the cheapest basic filters available, medium-efficiency MERV filters, such as the Nordic Pure MERV 12, can significantly reduce airborne dust, mold spores, pollen, and even smoke, and doing so can help alleviate respiratory conditions, according to an NIH review. It is important to note that the Environmental Protection Agency (EPA) does not recommend the routine use of homemade air filters as a permanent alternative to proven products (such as commercially available portable air filters).
