For me, there are 2 things that I feel is the most important when buying an air purifier.

1. HEPA filter - need to read carefully, make sure is a real HEPA because there are a lot of company claims HEPA filter but actually not, a lot of them are HEPA-alike filter. The main function of HEPA filter is to filter up particles (viruses and bacterial) found in air, and a HEPA filter is able to filter up 99.7% of 0.03 micron particles.

2. Active Carbon filter - used to filter up odour and make air fresh. Once air passes thru carbon filter, it contains a type of smell, some ppl might not get used to it but actually this is the smell of freshness.

The rest of the thing is not so important but is a plus to have:

1. Ionizer - Theorytically it releases negative charged ions to the air which is used to attach to particles in air and neutralise it, sounds good but I think it is more on marketing purposes. The truth is, the mechanism to release negative ion is real, a simple electronic circuit can cause sharp metal blade to produce negative ion easily and release them to the air. The problem is, the effectiveness are very much reduced by the humidity of the air, once the negative ion is released it will most probably neutralised by the water particles found in the air, only small portion of ions go for other particles. The other important thing is the amount of discharged ions, it has to be stay below a recommended amount, too much of negative ions will formed into ozone and this is harmful to lung.

2. UV - an additional protection to kill germs, but most of the germs are already filtered out at HEPA filter.

3. Humidity control - good to have if your room is under air conditioning most of the time, this is to prevent skin dryness. But increased in humidity will reduce the effectiveness of Ionizer, and also promote the grow of fungus and mold in the surrounding area.


There might be some other additional functions which I miss or don't know, before I bought an air filter 2 years back I did some study, and I found out some direct selling company even price their normal air filter at very high price, for eg Amway air filter at more than RM4k with prefilter, HEPA, and carbon filter, at the end I bought a sharp air filter FU2x at RM699.

Reasons are:

1. It is sharp, a well known company, reputation is very important to them.
2. It is cheap, and it has functions I need.
3. Nice design.
4. The same products have been selling worldwide and especially in US, we all know that US consumer takes their right seriously.

At the end, no regret, it works for me and my family, my parents bought Amway air filter at RM4888, tried it and feel the same, both works the same way, same result, but 1 priced affordable, 1 price at MLM level.

Hope this helps.