An air cleaner, also known as an air purifier, is an appliance that cleans the air by removing impurities. An air cleaner can clean the air in a single room, a whole house or an industrial workspace. Air cleaners are employed in situations where the air typically becomes unhealthy due to smoke, pets or pollutants such as molds, or when a work situation would otherwise be dangerous to the human operator, as when working with hazardous materials.
Air cleaners employ a variety of technologies to remove impurities from the air. The easiest to understand is the simple filter. The most common use of filters is in your home heating system, which employs a filter to clean the air before it returns to be reheated (or cooled).
Portable or room-sized air cleaners can also employ filters. These can remove impurities of different types, depending on the filter technology used. The finer (more tightly spaced) the filter material is, the smaller the airborne particles that it can remove from the air. HEPA filters, or High-Efficiency Particulate Arresting filters, are currently the finest and can therefore remove the most impurities. HOwever, gases and other pollutants will not be captured by HEPA filters.
Activated charcoal in an air cleaner can be used to remove gases and odor-causing small particles that a HEPA filter will not effect. Activated charcoal is a form of carbon that has been reduced to a very fine size. It interacts to bind pollutants and remove them from the medium (air or water) that passes through it; activated charcoal is often used in water filtration systems. It is also recommended in case of accidental poisoning; taking activated charcoal will cause the poison to bind to the carbon and pass harmlessly out of the system.
Some modern air cleaners fall into the 'ionic air purifier' category. Negative ions are associated with healthy air environments, around waterfalls and other rapidly moving water, or in the mountains. Airborne pollutants are positively charged, so the air in a smoggy city will have more positive charge than negative.
An 'ionic' air cleaner creates and releases negative ions into the air of your home. These negative ions bond with the positive air pollutant particles, causing them to fall out of the air. Of course, they're still in the room, as dust on the floor, walls or furniture. Most ionic air cleaners feature a filtration system to filter the air of the neutralized particles as well.
Selecting an appropriate air cleaner for your home should depend on several factors. If you or someone in your home has allergies, you will need to remove smaller particles than otherwise, which limits you to HEPA type filtering air cleaners, perhaps in conjunction with an activated charcoal filtering stage or ionic system.
If you plan to run the air cleaner in a bedroom, you will want to hear it running in the store to make sure it is quiet enough. A humming noise loud enough to keep you awake might mean you will turn off the air cleaner and waste your purchase price.