Methods of purifying air

Home air purification systems

Many everyday household activities such as dusting, cooking, smoking, vacuuming, burning wood on an open fire, and cleaning can increase the number of chemicals and airborne contaminants. Eventually these contaminants will end up in carpets or other types of fibre based flooring.

With the increase of double glazing, many houses are now practically draft-free which means that there is very little circulation of air from the outside, especially in winter when the only time fresh air is let into the house is when the front door is opened. The contaminants that build up can affect a person health, especially those who suffer from asthma, rhinitis, hay fever, eczema and multiple chemical sensitivity (MCS).

Particle Filters

As their name implies, particle filters are used to extract particles from the air. There are two main types of particle filter - HEPA or Electrostatic 

HEPA filters  (High Efficiency Particulate Arresting)

HEPA filters consist of a sieve-like filter material. The material is usually pleated and very dense. As the filter gets used, the density of the material increases as it gets clogged up with filtered particles. Eventually, it will need to be replaced (although they can last several years depending on the size of the filter). A true HEPA filter removes 99.7% of particles down to 0.3 microns. (A micron is 1/25,000 of an inch.) 99% of all particles found in the air measure less than 1 micron.

Electrostatic filters

Electrostatic filters act like a magnet attracting different sized particles. Electrostatic filters tend to be less dense HEPA filters. The effect of this is that up to 30% more air can pass through it. It therefore has a higher CADR (Clean Air Delivery Rate).

Odour and chemical air filters

Odour and chemical air filters are used to remove odours and chemical contaminants from the air. There are several types of filter under this category:

Carbon filters

Carbon filters are made of s substance called activated carbon (also known as activated charcoal or activated coal. This is a form of carbon that has been through a process to make it very porous. As a porous substance, it has a very large surface area available absorbing chemicals from the air. Carbon filters are usually used alongside particle filters thus filtering of both particles and chemicals.  Carbon filters usually need to be replaced every six to twelve months depending on their usage. Activated carbon is usually obtained from charcoal. Carbon filters will not absorb formaldehyde.

Zeolite filters

Zeolite is sometimes combined with carbon to create an even more efficient filter. Zeolite is a natural clay that is mined in the USA. Zeolite has three dimensional, microporous, crystalline structure. One of its key characteristics is that it is extremely effective at absorbing contaminants of a chemical nature as gases get trapped in the void porous cavities. Zeolite filters will absorb a range of chemicals including formaldehyde and VOCs (volatile organic compounds).

Plasma filters

Plasma filters are one of the best methods of filtration. They were first produced for medical use to limit the risk of allergies and other illnesses. They work by filtering out viruses and bacterial from internal air. Plasma is actually a mixture of electrically charged particles such as electrons, ions, and neutral radicals. These are all molecules that have high oxidation properties.

Plasma filters can destroy most bacteria such as those that cause Legionnaire's disease, viruses and fungal spores. It can also remove smoke and other particulate matter.

Titanium dioxide filters / UV light

As contaminated air flows over titanium dioxide coated mesh type filters, it is exposed to ultraviolet light.  The light energy from the UV light activates the titanium dioxide catalyst, which in tern generates hydroxyl radicals.  These radicals break down the contaminants into carbon dioxide and water.