When we talk about air purifiers we generally are discussing about either ionic air purifiers or HEPA air purifiers or may be the more controversial ozone air purifiers. This is normal as they represent the basic technology behind air purifiers and they should be treated with importance. But what tends to get left out in all these discussion is the importance of the pre-filter in an air purifier.

No matter how advanced an air purifier is, it needs to have a pre-filter. The pre-filters are built to capture any particulates floating in the air which are above the size of 5 microns. However some pre-filters are designed to trap particulates only above the size of 10 microns. Now particulates of that size would mean pre-filters are effective against pet hair and larger dust particles. But the question would be, why should we need an air filter at all since these particulates can be easily trapped by a normal filter. The answer would be, to protect the filters and let them do their job properly.

The filters built in any air purifier are built to trap much smaller particulates than the size of 5 or 10 microns. So they could have easily captured the pet hair or the larger dust particles. But using them for capturing particulates of larger sizes will significantly reduce their efficiency.

However, it would be wrong to imagine that having a pre filter would have been enough. Particulates of size above than 5 micron which remain suspended in air are very few. There would be approximately 400 to 800 particles of size equal or larger than 5 microns in about 1,000,000 particles. So the real job of removing particulates from the air still lies with the pores of the actual filter. The gas or carbon filters are therefore lined after the pre filter so that it can act on the smaller particulates better. It is the same with HEPA filters too.

The kind of air purifier you get for your room will depend on a few things. Depending on how much your budget is and how much you need it, you can decide on the filter. With HEPA filters, you will achieve 99.7 percent purity in the air you breathe. However, if your need is not that great or your budget demands you o be economical, you can go for the more basic filters. You should also remember the dimension of your room, as that will dictate the capacity of the air purifier.

We also must realize that a filter like HEPA filter are much too expensive to be removing particulates of size more than 1 micron. Using it for such particulates would be an utter waste of money. One should protect such expensive filters to do the more sophisticated cleansing.

Therefore, even if we don't pay much heed to the pre-filter in our air purifier, it plays a significant role in the efficient working of the purifier.