What Is HEPA Filter? How To Choose Right HEPA Filter?
Many people still ask themselves what is HEPA filter and should they pick air purifier which has HEPA filter? The term HEPA is an acronym for “High-Efficiency Particulate Air.”
HEPA filters are a standard tool used in many mechanical air cleaners to filter small, unwanted, and unhealthy particles out of the air. They consist of a web of fibers arranged in a random pattern.
The first HEPA filters were designed by United States Department of Energy in the 1940s. Somewhere around the 1950s they began to enjoy widespread commercial use. Since then, HEPA filters have evolved and improved significantly. But their basic design and function have remained the same.
True or Absolute HEPA Filters?
True/absolute HEPA filters must pass a test to be considered HEPA worthy. True HEPA filters will have a serial number assigned to them if they can trap at least 99.97 % of particles of .3 microns.
These test results are printed on the filter. True HEPA filters may be more expensive than other HEPA filters, but they must perform at a certain standard to receive True etiquette.
HEPA-Type Filters? HEPA type or HEPA-like filters are made in similar ways to True HEPA filters and may even resemble them.
But they do not have same standards as true HEPA filters. They often capture only 85 to 90 % of particles and that percent can fall even lower for particles of 1 micron and below.
HEPA-type filters are less expensive than true or absolute HEPA filters. HEPA filters must meet certain standards to be called HEPA, while “HEPA-type” could mean nearly anything.
How to Know Difference Between HEPA Type and HEPA True?
Look for the serial number and test results printed on true HEPA filters. Make sure that the test results at .3 microns are 99.97 % or above. The size of .3 microns is the testing standard because most filters will perform better with both smaller and larger particles.
Why Buy HEPA Filter? HEPA filters trap small particles that may cause problems for allergy sufferers and others with health problems.
Reducing or eliminating those particles will make the cleaner air in your home. Decide if a true HEPA is necessary for your family, or if capturing a smaller amount of particles is worth the price break on filter costs.
What is HEPA Filter? How It Works?
According to the online encyclopedia Wikipedia, air purifiers with HEPA filters operate differently than a typical membrane filter. Non-HEPA filters generally have only subtle pores, so that any bits of matter too large to fit through them are trapped.
HEPA filters, however, operate based on a different principle. The space between HEPA fibers is actually often much larger than the particles a HEPA filter targets.
Instead, HEPA filters catch particles through a combination of three different mechanisms:
1. Interception – most commonly affects particles above .4 microns. The particle sticks to one of the filter’s fibers after coming close enough to it. It is as if the fiber reaches out and catches the particle.
2. Impaction – most commonly affects particles above .4 microns. The particle is forced into contact with fiber by the trajectory of the airstream in which it is traveling, and is embedded into it. It is as if the particle makes a head-on collision with the fiber and then cannot dislodge itself.
3. Diffusion – most commonly affects particles below .1 microns. The arrangement of the fibers makes the particle collide with air or other gas molecules, and it is thrown off its course through the filter.
This is a means keeping the particle within the filter until one of the other two methods succeeds in ensnaring it. It is as if the particle is blown about by the wind until it collides with fiber.
Diagram information – Image shows the essential parts of a HEPA filter:
- Thick Brown Lines – represent fibers in the filter medium.
- Blue Lines – show the direction of air flow.
- Dark Circle – represents a particle like dust, bacteria, spore, etc.
- Dotted Red Line – represents the direction of the particle.
Is HEPA Filter Effective?
According to the United States Environmental Protection Agency (EPA), HEPA filters are the most efficient filter commonly found in mechanical air cleaners. However, the EPA also warns that using a stronger and more effective filter is no longer cost-efficient.
It claims that cleaners with a MERV rating from 7-13 “are likely to be almost as effective as true HEPA filters” for most ordinary purposes, and they will also be quieter and less expensive. Installing HEPA filters in large air cleaners will often require professional installation, further adding to the cost.
Also, in small, portable air purifiers, HEPA filters “may not be preferable to medium-efficiency filters because of HEPA filters’ lower air delivery.” Therefore, there are limits to the effectiveness of HEPA filters.
HEPA Filter Limitations
HEPA filters only target airborne particles, not gasses. Although this means that a HEPA filter will help clean the air of many common pollutants, it also means that many others will pass right through the filter undisturbed.
Many of the better air purifiers on the market will combine a HEPA filter with some other system that targets gaseous pollution, such as an activated carbon filter. Therefore, consumers are advised to consider their needs and all of the features of air purifiers before deciding which to buy.
HEPA filters tend to be more expensive than other filters. Filters will almost always need to be regularly replaced at least once or twice a year. That means there is an extra cost in addition to the initial price of the air purifier. This typically isn’t large, but over time it does add up.
How Much Can HEPA Filters Help?
Using a HEPA filter in your home can remove most airborne particles that might make allergies worse. But the particles in the air are not the only ones in your home. There are far more in your rugs, bedding, and drapes, and resting on countertops and tabletops. So it’s important to keep these areas clean. It’s also important to get rid of the source of allergens and irritants.
For example, the only effective way to keep tobacco smoke out of your home is not to smoke. These filters can be part of a plan to remove irritating particles from your home.
Other parts of that strategy should be to:
- Vacuum frequently
- Replace carpets with wood, tile, or vinyl flooring
- Keep pets outdoors if you are allergic to pet dander or at least away from your sleeping area
- Change bedding frequently and wash sheets in hot water
- Replace draperies and curtains with roll up shades
- Use plastic covers over mattresses and pillows
- Use high-efficiency furnace filters.
Things to Consider Before Buying a HEPA Purifier
If you’re looking to buy a HEPA purifier, there are several things worth noting:
1. Make sure it has genuine HEPA filtration by checking the particulate size quoted by the manufacturer.
Remember, that’s 99.97 % of particles at 0.3 microns filter is often described as “true HEPA” or “absolute HE.”
Avoid manufacturers who make vague, meaningless descriptions like “HEPA-like” and “HEPA-type” that aren’t quantified in any way. A true HEPA filter will always quote the numbers.
2. A purifier with proper HEPA filtration will channel virtually all (over 90 % ) of the dirty airstream through the HEPA filter.
If it doesn’t do this, the vacuum is simply rearranging the dirt.
3. Purifiers with true HEPA filtration need more powerful motors and ones with low power may not clean effectively. The filter will also need cleaning quite regularly.
4. Some professional-grade purifiers will have extra mechanisms for dealing with particles even smaller than 0.3 microns, such as activated carbon granules.
5. If you need industrial-strength air cleaning, there’s a tougher standard called ULPA (Ultra-Low Penetration Air) that can catch 99.99 percent of particles 0.12 microns and above.
What is a HEPA Filter Final Words
Anyone who makes many comparisons between different air purifiers will soon come across HEPA filters.
They are the most useful type of filter available for removing solid particles from the air. On the other hand, they are more expensive and are not effective at removing gasses.
For removing gasses look for an air purifier with carbon filter built-in along with True HEPA filter.
It would be a good idea to consider a purifier with a HEPA filter, especially in an ill-defined “HEPA-type” alternative, but be aware that there are limitations, and the presence of a HEPA filter does not by itself indicate that the purifier is a good one.
- HEPA filters only filter particles, not gasses
- HEPA-type filters may be a viable alternative due to being able to move more air through the filter quicker than standard HEPA filters
- HEPA filters tend to be more expensive – something to consider since air purifier filters require replacement over time
You can find HEPA filters in most air purifiers. These are small, portable units that may work for a single room.
If you are considering buying a HEPA filter, find out how much air that the filter can clean. Be sure you buy one that is big enough for the room where you plan to use it.
The best room for a unit is the one where you spend most of your time. You can find HEPA filters in most home improvement stores or online marketplaces.