Claims made by manufacturers of air purifiers often look great, but then the system itself may fail to live up to your expectations. Air quality is important to your and your family’s health, whether it is at home, kindergarten, school or workplace. Therefore, we put together some guidelines for you to consider, before you invest in an air purifier.
Theoretical versus actual efficiency of an air purifier. High efficiency particulate air (HEPA) is the key word these days when it comes to marketing an air purifier. HEPA air purifiers give excellent performance in hospitals and industrial clean rooms. But be cautious when an air purifier manufacturer claims that their home purifier removes ‘99%’ of air pollutants down to 0.3 microns. Often, the removal efficiency will be below 80% and sometimes even 50%. So why the claims of 99%? That is the theoretical efficiency of the filter material itself, used in the air purifier. There is usually a performance gap between what the manufacturer says and the actual air cleaner performance, because the filter is easily damaged, or is not actually a HEPA-rated filter, or there are leaks in the system and not all the air passes through the filter.
Overstating the air cleaners air delivery rates. Depending on the size your room, you need a certain amount of air per minute to be processed by the air purifier to guarantee a significant reduction in air pollutants. Often, the air handling capacity of the motor of the air purifier without filters is stated, rather than the actual airflow rate with the filters installed in the air purifier which would be lower of course (I know that that is odd and sounds like cheating). Few manufacturers state this particular performance specification, quoting instead the room size that they want their air purifier to be used in, but not saying how many air changes an hour you could expect in the room when the air purifier is in action.
ULPA versus HEPA air purifiers. Ultra Low Penetration Air (ULPA) technology can remove smaller particles than a HEPA filter, and with greater efficiency. Naturally, this has led some manufacturers to claim that ULPA-based air purifiers are superior. In fact, the ULPA air purifier tends to be less effective than the HEPA air purifier in a typical room. This is because there is a reduction in air flow caused by the denser ULPA filter. Typically, then, you’d get 20-50% less air going through the ULPA filter media than the HEPA filter, resulting in fewer air changes per hour.
Air purifiers with ineffective gas filtration. Gaseous contaminants and odours are a key component of indoor air pollution. Activated carbon is the main technology for removal of gaseous pollution. In its granular form, it is undoubtedly very effective. But did you know that many air purifiers contain only fibre pads impregnated with activated carbon dust. Carbon dust is not very effective in capturing gases and odours, because it is the granular structure that allows carbon to capture gases and chemicals effectively. It is also impossible for a mere activated carbon filter to remove all gaseous pollutants. You need a special sorbent for formaldehyde and ammonia.
Issues with the air purifiers long-term performance. The real value of an air purifier comes with its air cleaning effectiveness over months and years, not within the first few hours. But filters often suffer from ineffective pre-filtration, which causes them to get clogged up, thereby reducing air flow. If the air purifier has got a granular carbon filter, lack of pre-filtration will quickly lead to a loss of gas absorption potential. Some manufacturers will say you only need to replace your filter every three to five years. If you followed this, then your air purifier would be doing very little to improve air quality. Regular maintenance and filter replacement are needed to keep air purifier performance up.
Expensive, frequent filter replacement. While some air purifiers itself may be relatively inexpensive, cost of replacement filters can be quite steep. Lack of effective pre-filters often leads to clogging requiring replacement that is more frequent than it need be. Some filter cartridges are too small, and reduced capacity means low capacity for pollutants and increased frequency of replacement. And sometimes several filter stages are combined in one filter cartridge, so all filters have to be replaced, even if only one of them is used up.
One size does not fit all. Look at air purifier model ranges. Do the different systems differ in technology, or only in size? Can one unit really remove pet allergens, mould, tobacco smoke, odours and chemicals? Sometimes a manufacturer will say that use of several filter stages makes their air purifier more versatile. In fact, more filters mean more resistance to air flow and lower air delivery.
The take home message is, be very careful about the claims made by manufacturer of air purifiers. Look for independent evidence (not just other customer reviews) and test if the retailer really knows what they are talking about, that they really know what air purifier to use for your specific concern and budget.
Click here for FAQ about air purifiers.
