In general, we measure an air filter’s efficiency by its ability to capture particles from the air. But, to qualify as HEPA certified, air filters must first conform to the U.S. Department of Energy’s (DOE) standards.
Doe.gov defines HEPA filter as a throwaway, dry type filter in a rigid casing or enclosure. The device must exhibit an efficiency of at least 99.97% when tested with an aerosol of 0.3-micrometer diameter.
Many brands nowadays are using the word “HEPA” and “true HEPA” in the packaging of their products. Because of this, many homeowners end up believing that all types of air filters are the same. When in fact, they are not.
HEPA-type vs true HEPA filters
In this article, Morconnect talks about both HEPA-type and true HEPA filters. This is to help Ontario homeowners in choosing an air filter that is worthy of their investment.
HEPA-type or HEPA-like filters are air filters that do not meet the industry standards. Because of this, they have much lower efficiency in capturing air contaminants.
Filters are often rated by their Minimum Efficiency Reporting Value (MERV). It is a system that rates a filter’s ability to capture particles between 0.3 and 10 microns. In general, the higher the MERV rating, the better the filter efficiency is. A low-grade filter has a rating between 1 to 4 MERV while a medium ranking filter has a 5 to 12 MERV rating. Meanwhile, a high-rated filter has a MERV rating between 13 to 16.
Which one should you buy?
HEPA-type filters have a MERV rating of 16 and below. They may not be as efficient as true HEPA filters but they are still okay for some purposes. In fact, they also work fine in capturing large airborne particles like dust and dander. Hepa-type air filters act as a sieve as they can only trap large particulate matter from the air.
Meanwhile, true HEPA filters capture air particles as small as 0.3 microns with 99.97% efficiency. They have a MERV rating of at least 17.
True HEPA filters have dense fiberglass threads compressed in random patterns. They work by trapping particles into the pleats of the fibrous medium. There are three different filtration processes that happen inside a true HEPA filter. The first one is inertial impaction. This occurs when large particulate matter attaches itself to the filter’s fiber. The second process is an interception. This happens when smaller particles try to flow around the fiber pleats and get stuck. The third one is diffusion. This is for the smallest of all particles that traverse the flow stream. As they move through Brownian motion, they collide and get stuck into the fibers.
When purchasing an air filter, it is important to be aware of the terms that marketers put into their labels. The key is to look for details saying that the device is HEPA certified. It is even better if the label specifies that the air filter can capture 99.97% of all particles at 0.3 microns in size. You should also think twice if the price of the air filter you are looking at is too good to be true. Air filters from top brands are not cheap. In fact, some models can cost a few thousand dollars and more.
In conclusion, not all HEPA-labeled air filters are the same. With so many options in the market, it can be tough to find an air filter that is both effective and safe. As a smart consumer, you must look for true HEPA specifications or UL certifications. If in doubt, it may be in your best interest to stick with air purifiers from trusted brands for added peace of mind. If you have the budget, spending on a more expensive air filter will prove to be a worthy investment in the long run. Last but not the least, you may also talk to an HVAC expert like the ones at Morconnect and ask for their advice.