Air purifiers that use only high-efficiency particulate air filters (HEPA filters) do not emit ozone to clean the air. Ionizing air purifiers, due to their electrical charge, create ozone. Consumer Reports has warned that they can emit potentially harmful ozone levels. 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 remove particles from the air. They do this by causing particles to adhere to nearby surfaces or to each other and deposit out of the air, but they can generate unwanted ozone. This fact sheet provides information on air purifiers, including the different technologies used, selection and use.
Using air purifiers can be an important strategy to help improve indoor air quality (IAQ). For additional information on IAQ, see the EH%26S guide on IAQ. Ozone is a colorless gas that occurs naturally in the Earth's upper atmosphere and protects us from harmful ultraviolet solar rays, although it can also form at ground level. It is known to cause the formation of free radicals in biological systems, which damage tissues.
One mechanism of damage is the result of ozone-olefin reactions, and another from the reaction of ozone with electron donors (such as glutathione). Inhaling relatively small amounts of ozone can cause coughing, chest pain, throat irritation, and shortness of breath. Ozone generating air purifiers are devices that purposely create ozone to clean the air through chemical interactions that alter the compounds of pollutants, but this is also the mechanism by which ozone exerts harmful health effects. In addition, ozone is generally ineffective in controlling indoor air pollution at lower concentrations.
In other words, if the ozone concentration in the room is high enough to be effective in cleaning the air, it is also high enough to create an inhalation hazard for people in the room. In addition, ozone can even react with chemicals in the air to create harmful by-products (for example,. For these reasons, EH%26S does not recommend the use of electronic air purifiers or ozone generators under any circumstances. Electronic air cleaners (including ionizers, electrostatic precipitators, hydroxyl generators, and ultraviolet light) use electrical voltage to convert oxygen molecules, or other species, into their charged ionic components that inactivate airborne pollutants, in a process called bipolar ionization (BPI).
The ionic components of oxygen are reactive radicals that are capable of removing hydrogen from other molecules. In the case of bipolar ionization, positive and negative ions surround air particles, destroying current germs and pathogens, and the aggregate mass helps air particles fall to the ground and enter the building's air filter. However, BPI can emit ozone and other free-radical species as a by-product, and may be less effective than other cleaning technologies, since charged particles in the air sometimes adhere to room surfaces (e.g. floors and walls) instead of leaking.
Filtering air filters pass air through a filter, where polluting particles or gases are sequestered, and return clean air to a room. There is some popular controversy surrounding the extent to which air purifiers can reduce the presence of larger particles (such as pollen, house dust allergens, mold spores, and animal dander), but most of these large particles are deposited on home or office surfaces and cannot be removed with an air cleaner unless altered and resuspended in the air. Therefore, regular cleaning is the best way to eliminate the biggest allergens. Air cleaning units have air volume limitations that are identified by a “Clean Air Supply Rate” (CADR).
A CADR is the cubic foot per minute (CFM) of air from which all particles of a given size distribution have been removed. CADR indicates the volume of filtered air delivered by an air cleaner per unit of time, with three separate scores for smoke, pollen and dust, representing different particle sizes. The higher the CADR number for each pollutant, the faster the unit filters the air for contaminants in a given size range. A carbon filter is the most suitable unit for cleaning gaseous VOCs from the air, for example, when new furniture is released from gases.
However, if you notice an odor in a room, contact EH%26S first for an evaluation. The best course of action is to eliminate and control the source of the odor, and EH%26S can conduct an evaluation to do so and develop a remediation plan. HEPA filters are better at cleaning particles from the air. 0.3 micron diameter specification is worst-case, or most penetrating particle size (MPPS).
Particles that are larger or smaller are trapped with even greater efficiency. Using the worst particle size results in the worst-case efficiency rating (i.e. Minimum Efficiency Report, or MERV, values report a filter's ability to capture larger particles between 0.3 and 10 microns (µm). EH%26S recommends HEPA filters for particles and aerosols.
All filters need to be replaced regularly as specified by the manufacturer in the product user's manual. If a filter is dirty and overloaded, it will not work well. With proper care and maintenance, the portable air purifier will continue to work properly and filter the air. Consider buying replacement filters with the air filter.
Carbon filters can passively absorb VOCs from the air, so make sure they remain sealed until installed in the unit to extend the life of the unit. According to the EPA, there is currently no evidence to suggest that a reasonable number of indoor plants would be effective in removing significant amounts of pollutants from indoor air. Indoor plants should not be over-watered, as too moist soil can promote the growth of microorganisms that can affect allergy sufferers. Ionizer air purifiers are generally safe because ionizers are not energized enough to be harmful to you.
These ionizers turn on for 8 hours every day, and I have a Therapure TPP300D with UV+ ionizer that turns on for 8 hours in my living room. However, to get rid of the dangers of second and third hand smoking from my roommate, I now plan to keep my ionizer turned on only for 30-40 minutes when no one is in the room, and then turn off the ionizer before anyone comes in. Air ionizers are designed to help provide cleaner air and they do so through the use of ionized particles. Since the conflicting data associated with the ionizer remains persistent, I usually keep my ionizer option turned off.