Why can't you be in a room with an ionizer?

You can be in a room with an ionizer, but there are reasons why staying for long periods in a small sealed room with certain types of ionizers is discouraged, mainly due to ozone production and particle behavior. Many ionizers, especially cheap ionizers, electrostatic precipitators, and ozone generators marketed as air purifiers, produce ozone as a byproduct of charging ions. Ozone above 0.05 ppm irritates eyes, nose, throat, and lungs, causing coughing, chest tightness, shortness of breath, and worsening asthma, and long-term exposure can cause permanent lung damage. In a small closed room with no ventilation, ozone can accumulate to unhealthy levels quickly. Another reason is that ionizers do not actually remove particles like a True HEPA filter does, they charge particles so they stick to walls, ceilings, furniture, and potentially your lungs, creating a dirty film and not truly cleaning the air, and settled particles can be resuspended. For people with asthma, children, elderly, and pregnant individuals, this can trigger symptoms. Some people also experience headaches or irritation from high ion concentrations. If you use an ionizer, choose one certified by the California Air Resources Board to produce less than 0.05 ppm ozone, keep the room ventilated, do not run it continuously on high in a small bedroom, and clean surfaces regularly. For mold, dust, and allergen removal, a True HEPA purifier without ionizer is safer and more effective for prolonged occupancy.