HEPA air cleaners - widely used, but are they cost effective?

The first High Efficiency Particulate Air (HEPA) air cleaner was designed in the 1940’s. At the time the goal was to be able to filter out 99.97% of radioactive particles greater than 0.3 micron, and most present day HEPA air purifiers still have the same specification.
For comparison, the width of a human hair ranges from 50 to 200 microns, so 0.3 micron sounds pretty good and should keep most allergen at bay – right?

Some important points to consider
Without a doubt HEPA filters are very efficient at filtering allergen such as pollen, dust, and mold spores.
However, more than 90% of all particulates are 0.3 micron and smaller in size which means that HEPA air cleaners do not remove viruses, some bacteria and germs, some house dust mite allergens, cat allergens, smoke, soot, fumes, and smog.

It should be noted though, that HEPA air cleaners do remove particulates smaller than 0.3 micron, some of them filter down to as small as 0.01 micron, but the percentage of particles removed drops off rather quickly.

If you want better performance than that with a standard HEPA air purifier, there are more expensive units on the market with exceptional performance.
For instance, the IQAir HealthPro has a low noise design and a filter that will last a minimum of 5 years. Furthermore, the filter is guaranteed to capture at least 95% of all particles smaller than .3 microns, so even viruses are caught.

There are some drawbacks to HEPA air purifiers however:

• Although a prefilter extends it’s life, regular filter replacement is required every 2-5 years.
• Filters cost on average between $50 - $100.
• The mechanical process of moving air through a dense filter requires a large, powerful fan. That means relatively high energy requirements, and therefore a high energy bill: $100-$300 per annum.
• Can be very noisy if run at the highest level, which would occur if the unit is undersized relative to the room.
• Filters are extremely fragile and can be easily damaged.

Some HEPA air purifiers include other air cleaning technologies to complement the HEPA filter. 
For instance, to remove odors a HEPA air purifier could also have a gas filter made of activated carbon, potassium permanganate, or zeolite. The Austin Air Healthmate and the IQAir HealthPro are examples of such a hybrid model.

All in all, while HEPA air cleaners have some drawbacks, together with electrical air purifiers, they are for most people the best overall solution to improving indoor air quality.

Look for quality brands such as Honeywell, IQAir, Holmes, Hunter, and Austin.