Most commercial air purifiers use a mechanical process to pass the air through filters where potentially harmful particles are collected. In purifiers using HEPA-grade filters, like those from Metalmark, 99.97% or more of particles are captured.
Two other currently popular air purifier technologies, though, use electronic technologies.
- UV air purifiers typically use filters, including HEPA filters, to capture unwanted particles. They then expose the captured particles to UV light which can damage the DNA of microorganisms.
- Bipolar ionization (also called needlepoint bipolar ionization) applies electricity to produce positive and negative ions. These ions then charge airborne particles causing them to aggregate and fall out of the air. Bipolar ionization systems are sometimes combined with mechanical filters and manufacturers claim that their technology improves the MERV rating of those filters. Proponents of bipolar ionization claim that they may also damage airborne viruses and bacteria.
UV air purifier manufacturers claim results from damaging the DNA of viruses and bacteria. However, these UV rays also accelerate the degradation of filters, thereby requiring more frequent filter changes.
In terms of bipolar ionization, Boeing ran tests and concluded, “The use of air ionization in an airplane remains inconclusive as a methodology for deployment during the SARS-CoV-2 virus pandemic. Boeing’s limited testing was unable to replicate supplier results in terms of antimicrobial effectiveness. The systems were unable to properly deliver and maintain the necessary ion levels in the airplane to achieve disinfection. Similarly, laboratory-based tests did not show proper rates of disinfection with higher ion concentrations.”
The EPA writes that, “Bipolar ionization has the potential to generate ozone and other potentially harmful by-products indoors, unless specific precautions are taken in the product design and maintenance.” Ozone can produce chest pains, coughing, and throat irritation, and contribute to health problems like asthma, bronchitis, and emphysema. Since air purification systems are often not well maintained, for these reasons alone it may be a good idea to avoid bipolar ionizers.
And ASHRAE writes, “Convincing scientifically-rigorous, peer-reviewed studies do not currently exist on (bipolar ionization); manufacturer data should be carefully considered. Systems may emit ozone, some at high levels. Manufacturers are likely to have ozone generation test data.”
HEPA-grade filters, which are used in Metalmark’s Tatama® self-cleaning commercial air purifiers, remain the gold standard.
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