Despite manufacturers' claims, ozone air purifiers don't remove asthma triggers from the air. In fact, inhaled ozone can make asthma worse.

Ozone generators sold as air purifiers intentionally produce the gas ozone. Ozone can mask odors by changing the chemical composition of particles or other gasses in the air, making the air seem fresher and cleaner. However, ozone generators don't actually filter out the small particles that trigger asthma.

Inhaling ozone, even in small amounts, can irritate the lungs. Specific effects may include throat irritation, coughing, chest pain and shortness of breath, as well as an increased risk of respiratory infections.

Some ozone air purifiers are made with an ion generator, sometimes called an ionizer, in the same unit. You can also buy ionizers as separate units. Ionizers do remove particles from the air. They do this by causing particles to attach to nearby surfaces or to each other and settle out of the air — but they may generate unwanted ozone.

Air filters that remove small particles — such as high-efficiency particulate air (HEPA) filters — are effective in removing allergens from the air, without posing any ozone concerns. To work effectively, filters need to be cleaned or replaced regularly, according to the manufacturer's instructions.