What happens if you stay in a room with an ionizer?

If you stay in a room with an ionizer, what happens depends on the type of ionizer and whether it produces ozone as a byproduct. In a room with a low-ozone negative ionizer that is certified to produce less than 0.05 ppm ozone, most people will not notice any immediate effects, and the ionizer will cause airborne particles like dust and pollen to clump and settle onto surfaces, which may make the air feel fresher temporarily, similar to air near a waterfall. Some people report improved mood or less stuffiness due to reduced particles. However, if the ionizer produces significant ozone, which many cheap ionizers, electrostatic precipitators, and ozone generators do, staying in a closed room can cause irritation of the eyes, nose, and throat, coughing, chest tightness, shortness of breath, and worsening of asthma, because ozone is a strong oxidizer that damages lung tissue. With long-term exposure to elevated ozone above 0.05 ppm, you may develop chronic respiratory issues and increased susceptibility to infections. Ionizers also cause particles to stick to walls and furniture, creating a dirty film, and settled particles can be resuspended when disturbed. For mold or chemical odors, an ionizer alone will not remove the source. If you must use an ionizer, use a certified low-ozone model, keep the room ventilated, do not run it continuously in a small sealed bedroom, and consider using a True HEPA filter instead, which captures particles without producing ozone and is safer for prolonged occupancy, especially for children, elderly, and those with respiratory conditions.