Air purifiers are the latest gadget that most Americans are picking off the shelves from the electronic stores. As the levels of air pollution indoors rising to alarming levels, this seems a prudent choice. More and more Americans are bringing one for their home. But though the sales have increased, very few users are yet not too clear about the technology of the gadget and how it works.

One of the key components of any air purifier is the filter inside it. This is where everything gets trapped and the real cleansing takes place. So the filter has to be in the best possible condition all the time. However, this is not always feasible as you cannot change the filter every day. So what we can at most expect is to have the filter deliver optimal results over a period of time.

Now how would you know that your filter have had enough and it is time for replacing the same. In previous models it was guesswork. And guessing this is not always easy as an average citizen would not have the knowledge necessary to make the call. You can do it after a fixed period of time, but that wouldn't be too sensible. The amount of work the filter had done varies from one house to another. If there is more traffic in a room, there are pets in the house, the filter will be used more. However if the room is relatively less occupied then the filter will be having an easy time and should last longer.

With older models it was actually expected that you will be able to trace with your naked eye the number of particulates increasing as the filter wears out. But that is neither very scientific nor very authentic. Or you were expected to smell the odor to judge if it is time for replacing the filter. With an indicator light, all these hassles are thrown out of the window.

An advanced HEPA air purifier will have at least four filters - a pre-filter, a gas filter, the actual HEPA filter and the final post filter. The latest models are now coming with indicator lights for each of these filters. So now you know exactly which filter to replace and which you can keep for a few more months. This will save you from having filters which are all clogged up and performing no function or from changing your filters too soon which become unnecessary expenses for you.