Do negative ion air purifiers really work?

Negative ion air purifiers do work to some extent at removing particles from the air, but they work differently than True HEPA filters and have important limitations. Negative ion purifiers work by emitting negatively charged ions that attach to positively charged airborne particles like dust, pollen, and smoke, making them heavier so they clump together and fall out of the air onto surfaces like walls, floors, and furniture, rather than being captured in a filter. Studies show they can reduce fine particle counts in a small sealed room by 20 to 50 percent, but they are much less effective than True HEPA purifiers which capture 99.97 percent of particles down to 0.3 microns inside a filter. Ionizers do not remove gases, odors, VOCs, or kill mold at the source, they just make particles settle, which means you still need to dust and vacuum frequently, and settled particles can be resuspended. The biggest concern is that many ionizers produce ozone as a byproduct, which is a lung irritant that can worsen asthma and cause coughing and chest tightness, and ozone levels above 0.05 ppm are considered unhealthy. Some ionizers also produce ultrafine particles. For mold removal, ionizers alone are not recommended by the EPA or IICRC, because they do not physically remove spores and can give a false sense of clean air. For best results, choose a True HEPA air purifier certified low-ozone, and if you use an ionizer, use it as a supplement with good ventilation, not as your primary purifier.