I would like to help you look more critically at air purifiers claiming to use HEPA air filters. Why? Because HEPA filtration is the best available, but the way it is used may leave much to be desired.
Consider an example. A man may have a well-appointed kitchen with the best of ingredients but this doesn’t make him a chef. Nor does it mean anything he prepares will even be edible.
Likewise, using HEPA air filters doesn’t guarantee the end result will really clean the air. Unfortunately, many manufacturers continue to produce inferior products while playing lip service to quality and customer expectations.
What kind of questions should you ask about any HEPA air purifier you may be considering?
What is the size of the HEPA air filters?
One of the most difficult to find pieces of information about a HEPA air purifier is the actual size of the filter. Most manufacturers don’t reveal it. Perhaps they feel it isn’t important. Perhaps they fear it will result in consumers comparing their product unfavorably against competitors.
Why is size important? Quite simply, because the bigger a filter is the more particles it can remove before it clogs. Also, the bigger a filter is the more air it can clean in a single pass.
Lastly, a bigger filter will present less back pressure to the fan that pushes the air through the filter. Back pressure puts a load on the fan motor. Cheaper motors may fail as a result. Manufacturers avoid this by letting some air escape around, or bypass, the filter. This is air that isn’t being cleaned.
Simply put, bigger HEPA air filters mean cleaner air and longer life of both the filter and the air purifier leading to reduced total cost of ownership.
What is the quality of the HEPA air filters?
The material used, the design and methods of manufacture are all important to the quality of the HEPA filter.
The highest quality manufacturers make certain that their HEPA filters have evenly spaced pleats, often with separators to ensure that the pleats remain uniform over the life of the filter. This is because if pleats are uneven, those that are closer together will restrict airflow and reduce cleaning capacity.
Some HEPA filters are made from synthetic materials. However the best filters are still made from a delicate, thin paper because it removes the highest percentage of particles with the least restriction of airflow.
This paper can be easily damaged during manufacture of the filter and assembly of the air purifier. The best filters are produced with a technique known as “warm rolled”. This prevents damage to the media during filter construction. Higher quality air purifiers will house the filter in such a way that it is protected from possible damage during assembly and use of the air cleaner.
What is the efficiency of the air purifier?
There isn’t a HEPA filter air purifier on the market that doesn’t proudly announce that HEPA filters remove 99.97% of particles as small as 0.3 micron.
Yes, but, what does the air purifier remove?
In some HEPA based air cleaners as much as 40% to 50% of air entering the cleaner may actually bypass the filter. Reasons for this range from poor sealing of the filter in the housing, cracks in the filter and even deliberate design to reduce backpressure on an inferior motor.
Virtually all air purifiers on the market using HEPA air filters provide no documentation on the efficiency of the unit as a whole. This situation is unacceptable. You as a consumer have no way of knowing how effective any given machine is.
The most notable exception is IQAir. Their HealthPro series have been independently tested and certified as to efficiency. In fact each and every unit is tested and certified and sent with documentation showing its effectiveness.
Another high quality air purifier that is independently certified is the Allerair AirMedic. Both Allerair and IQAir have shown a real commitment to the overall quality of their air purifiers and your satisfaction. Other companies that meet the criteria outlined in this article are BlueAir and Austin Air.
What kind of protective prefilter is used?
While the HEPA filter is the heart of the air purifier you should never overlook the importance of the pre-filter. A high quality pre-filter protects the HEPA air filter and any gas phase filter from becoming prematurely clogged. This means it protects your investment and saves you money!
Most pre-filters remove particulates 5 to 10 microns and larger. Of course, the percentage of particulates in the air that are 5 microns and larger is very small. For every 1,000,000 particles per cubic foot of air there is normally only around 400 to 800 particles that are 5 microns and larger.
As a result, much of the particulate removal is still left for the Hepa filter. The Hepa filter is too expensive a filter to be used to remove particles larger than 1 micron. You should consider the filter efficiencies of the pre-filter in selecting an air purifier.
The best example of a pre-filter is the one on the IQAir Healthpro which is 100% efficient at removing particles 1 micron and larger. In addition, it is 55% efficient at removing particulates 0.3 of a micron and larger. This pre-filter will remove 90% of all of the particles in the air and prolongs the life of the Hepa filter.