Ionizers are devices that disperse negatively or positively charged ions which attach to particles in the air. The particulate matter is then collected by the ionizer or attaches to nearby surfaces. Ionizers are typically sold as "air purifiers" that remove allergen or asthma-inducing particles from the air. However, ionizers are not as effective at removing airborne particles as air purification devices that use high-efficiency particulate air, or HEPA, filters. Additionally, ionizers may also produce ozone, which can cause or worsen respiratory problems.
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Effects on Allergies
Although ionizers are often advertised as devices that help improve allergy symptoms by removing allergen particles from the air, they have not proven to be particularly effective. While these devices do remove some small particles from the air, such as those found in tobacco smoke, they may be ineffective at removing the larger particles such as pollen and house dust allergens.
Because ionizers remove some types of airborne particles, they have also been marketed as methods of reducing asthma symptoms. However, ionizers can actually make asthma symptoms worse in a couple of ways. Small particles charged by ionizers, rather than being collected, are sometimes left suspended in the air, which can exacerbate asthma symptoms. Secondly, ionization may generate ozone as a byproduct, which can worsen asthma symptoms and other respiratory problems. Air purifiers that use HEPA filters are preferred over ionizers, as they effectively remove particulates from the air without posing any ozone risks.
Mental Health Effects
Ionizers have also been studied for their effects on certain mental health conditions, including depression and anxiety, as well as their effects on sleep and personal comfort. Experimental research suggests that anxiety and severity of depression decreases with exposure to negatively charged air ions, however findings are inconsistent. More research is needed to examine the potential positive mental health effects of ionizers.
Effects on Infection Transmission
One area in which ionizers have demonstrated some beneficial health effects is in controlling the spread of infection in hospital settings. A study published in "BMC Infectious Diseases" in 2010 found that use of a negative air ionizer significantly reduced infection-causing bacteria on plastic medical equipment. The study concluded that the use of ionizers in medical settings may help reduce the risk of disease transmission via infected equipment.