Air purifiers - what type is best for me?

The house we live in dates back to before Victorian times.  It was once three workman's cottages which were knocked together and then converted into two flats, one above the other.  We live on the ground floor flat.  It's a great house, with lots of character, but unfortunately - due to its age - it doesn't have a damp course.  So we therefore have a bit of a problem with damp and mould.  Most rooms are OK, but the bedroom, which is partly below street level, suffers the worst.   For the first few years of living in the house, I would regularly have to check the clothes in the bedroom wardrobe to see whether they'd developed spots of mould!   As well as finding it inconvenient to have to do a "mould check" on our clothes every couple of weeks, I was also worried about the possible long-term health effects of sleeping in such a room. 

So I looked around for solutions, and hit on the idea of buying an air purifier.  When I did some research on the best type of home air purifier to buy, it proved to be quite hard to pick my way through all the options.  I eventually made a decision that I'm still happy with five years on (more on this below), but it took me a loooong time to get the initial research done!  So if you too are considering investing in an air purifier, this hub is designed to help you clarify your thoughts.

The first question you need to ask yourself is "What do I want my air purifier to be able to do?"  Do you want it to remove allergens, mould spores, bacteria and perhaps viruses as well?  Do you also want to get rid of smells/cigarette fumes? Your answer to these questions will determine the type of purifier you buy, along with other factors like cost (naturally), convenience, noise and the square footage it can deal with.

A note on square footage

For most of the air purifiers I've featured, I've quoted the square footage that the model is capable of covering. For reference, a typical living room is 12 feet by 12 feet, so its square footage is 12 x 12 = 144 square feet. If you need to purify the air throughout the whole of your house or apartment, bear in mind that you might need to buy several air purifiers! Or consider buying one with a really large coverage - say, over 1,000 square feet.

Types of air purifier technology

There are five types of air purifier technology that I'm going to describe in this hub, and many air purifiers on the market nowadays incorporate two or more of these. The main ways in which an air purifier can work are as follows:

1. Filtration. There are two main types of filters used in air purifiers: HEPA filters (HEPA = High Efficiency Particulate Air) and carbon filters. These days, many models of air purifier will have both a HEPA filter and a carbon pre-filter. HEPA filters are made from a kind of cloth comprising randomly-arranged fibres that trap allergen particles and some bacteria by adsorbing them on the cloth's surface. However, HEPA filters don't trap viruses, cigarette smoke, chemical fumes or general smells. Carbon filters do remove some allergens and bacteria (not all though) but unlike HEPA filters, they do cut down on chemical fumes and odours, including cigarette smoke. Carbon filters and pre-filters need replacing regularly, while HEPA filters need to be replaced less frequently, if at all.

2. Ozone generation. As the name suggests, ozone air purifiers generate ozone which reacts with air pollutants such as odour molecules, breaking them down chemically. One caveat with ozone purifiers is the fact that ozone is actually harmful if you inhale it in large quantities! (In fact, it's been known to trigger asthma attacks.) So if you're using an ozone air purifier in a room that you spend a lot of time in, you might want to run it on "low" (unless you can evacuate the room altogether while the machine is on) and remember to open the window after any smell has gone.

3. Ionisation. Air ionisers give a negative charge to any air molecules in their vicinity. As these molecules circulate, they adhere to any positively-charged particles in the air, resulting in a heavier particle that falls to the floor. This can actually result in a dust problem so to get round this, many ionisers contain precipitators which trap such particles before they hit the ground or your furniture.

4. UV (ultra violet) light. UV light has a sterilising effect, so that any viruses, bacteria and mould that come into contact with it can no longer reproduce. UV light has no effect on allergens like pollen or on odours/smoke.

5. Incineration. In this air purification method, air is sucked through a heated ceramic unit which simply burns off any mould spores, pet dander, bacteria, pollen etc. before re-releasing the resulting harmless material back into the air. This was the type of air purifier I eventually decided to buy, after doing all that research - the one I actually bought was an Airfree, a precursor to the current Airfree P1000. The two things that sold me were (a) the fact that it actually destroys mould spores etc, rather than just trapping them somewhere, and (b) the convenience factor: there are no filters to replace. Ever. This also means that even though this isn't necessarily the cheapest type of air purifier to buy upfront, it has almost no running costs! The other plus points are that it's "plug and play", makes no noise at all, and it doesn't generate ozone (in fact, it actually reduces ozone levels according to the blurb). Drawbacks? Well, it's cut down the slightly musty "damp" smell in the bedroom, but it hasn't removed it altogether. You do also have to leave it plugged in 24/7 and the manual recommends that you don't ever move it, because it takes time to set up a suitable convection cycle. But if you're happy under those constraints, then I would recommend it.

© Empress Felicity  June 2010

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