There are many different kinds of air purifiers in the market today, each of them working with different principles. The concept of purifying air within homes has caught on in the aftermath of World War II when people were trying to devise techniques that could prevent the harmful radioactive dust that would enter their homes. These filters were mostly particulate repellants. It was later that air purifier designs began to undergo modifications and developments so that they could rid the room air of most other forms of pollutants also. Today’s air purifiers can clean the indoor space of not only particulate matter such as dust, spores, dander, pollen, etc. but they can also prevent harmful gases and microorganisms from entering homes. Some air purifiers use more than one technology in conjunction with each other so that they can better purify the air in indoor areas.
Activated charcoal was the oldest substance used in air purifiers and is used even today. This is an adsorbent for most gaseous matter. When air is passed over activated charcoal, it can form chemical bonds with the pollutants present in it. Therefore, it prevents these matters from polluting the indoor space. Activated charcoal essentially converts the gases into a solid form and accumulates it. It needs regular cleaning so that these matters can be removed. Such purifiers have an edge over other purifiers because they work even if it is just kept in a corner of the room. It is not necessary to actually pass all the air through it; activated charcoal will attract the pollutants from its nearby area and form bonds with it.
However, activated charcoal needs to come to a particular level of saturation before it can effectively start adsorbing the pollutants. This can take some time during which most pollutants will have wended their way into the room and wreaked their havoc. Activated charcoal filters are also incapable of removing bulkier pollutants from the air, though they are very efficient at removing fumes from the environment such as cigarette smoke.
HEPA (High Efficiency Particulate Air) filters are much in demand nowadays. These are physical filters that can stop pollutants from entering the room. They are installed in vents and all the air is passed through it. Being physical filters, they can only remove particulate matter from the air that actually passes through them. Hence, the manner of installation of these filters is of importance.
The standards of HEPA are controlled by the government. Cheap imitations of HEPA filters are abundantly available but since most of them do not conform to required standards, they are not recommended. HEPA filters are efficient at stopping big sized particles from entering rooms, but they cannot stop gases and fumes. In that manner, they are exactly complementary to activated charcoal. For that reason, air purifier units containing both activated charcoal and HEPA filters are designed so that they can better prevent particulate matter as well as gases from polluting an indoor environment.
A recent development with air purifiers are the air ionizers. They have needle-shape arrangements which can discharge ions into the environment. Ions are incomplete molecules; they will look for other molecules to bond with so that they can complete their chemical deficiency. Once released in the environment, the ions will bond with pollutant molecules, thus making them bulkier. These bulkier molecules are then drawn toward the purifier where they are collected and later removed.
Air ionizers are considered to be very efficient because they work at removing large particulate matter as well as gases and fumes from the environment. They are also low-maintenance, because they can simply be washed or cleaned by vacuuming and require no replacement.