What Is a HEPA Filter and What Does It Do?


Air Filters

While shopping for air filters I have often noticed that some of them have the word HEPA written on the packaging. Since my wife has multiple airborne allergies I decided to do some research to see if HEPA filters are something that she might benefit from. So what is a HEPA filter?

The word HEPA is an air filter efficiency standard that is an acronym for “high-efficiency particulate arresting.” True HEPA filters are rated to trap harmful particles or allergens as small as .3 microns at a rate of 99.97% or higher and are not associated with a particular brand or type of construction.

Besides the efficiency of a filter, there is much more to consider when deciding what type to use. After all, whether you have bad allergies or not, anyone can benefit from breathing cleaner air in their home or workplace. Let’s take a look at a few other factors pertaining to filters.

How Do HEPA Filters Work?

Typically, HEPA filters use three different mechanisms to catch particles. There is an outer sieve-like layer that mainly stops the larger particles like dust or hair. The inside is not made of paper but rather is usually a mat of ultra-fine glass fibers.

Within the outer layers are usually a material that is heavily folded that is designed to trap finer particles. Inside, the gaps in the filter are actually much larger than the particles. However, due to the way a true HEPA filter is made, 99.97% of particles will still be stopped since some impact directly on the fibers and others get caught up as they brush by. The mechanisms are called impact, interception, and diffusion.

In laymen’s terms, HEPA filters are built more robustly and have more ways of catching airborne particles and allergens than standard filters.

Are HEPA Filters Effective for People with Allergies?

HEPA filters are but one tool in a person’s arsenal in dealing with allergens. They are usually very good at removing pet dander, dust mites, and pollen. However, while they do indeed remove more particles from the air, this can only happen if they actually pass through the filter.

Many allergens accumulate in carpets, bedding, and furniture or are simply resting on tables or counter-tops. Even so, using a HEPA filter in an air purifier or vacuum cleaner is a proactive way to deal with and lessen the amount of potentially harmful airborne particles that you might encounter.

What Is the Difference Between HEPA Filters and a Standard Filter?

Regardless of the brand name or construction the difference between standard and HEPA filters lies solely in the efficiency in which the filter traps particles by size and frequency.

Regardless of promises made on the label, if a filter does not trap at least .3 microns at a 99.97% rate, it is not a HEPA filter and is instead to be considered “standard.”

Unfortunately, while some filters claim to be HEPA, sometimes it is not the case. Be sure to check the label to make sure the product will trap particles that are as small as .3 microns at a rate of 99.97% or higher.

What Products Are HEPA Filters Used In?

Today, most HEPA filters are associated with indoor air cleaners or purifiers. However, true HEPA quality filters are available in nearly every type of filter.

Products That May Have HEPA Filters Available:

  • Vacuum Cleaners: Note: some vacuums filter out particles above the HEPA level and do not require special filters
  • Air Purifiers: Air purifiers come in all different shapes, sizes, and qualities. Watch out for misleading labeling and look for true or absolute filters.
  • Home Air Filters: It’s really difficult to find any home air filters with HEPA labeling, although many brands have high-end versions that claim to remove particles at or near the same rate.
  • Car Cabin Air Filters: Supposedly, only the Tesla Model X has a true HEPA cabin air filter available. Even so, most cabin filters are typically rated an 8 on the MERV scale.

How Long Do HEPA Air Filters Last?

Most HEPA air filters will actually have a shorter lifespan than standard filters. This is because they trap more particles and thus fill up faster. Depending on the type of filter, it is recommended that they are checked every 60-90 days to see if a replacement is warranted.

There are also so-called permanent HEPA filters that can either be cleaned or even washed. Permanent filters are typically cleaned every two months. Washable filters can last three to five years and “permanent” ones up to 10 years.

How Do Make Sure I Buy a Real HEPA Filter?

HEPA filters typically are labeled “true” or “absolute” and often come with test results printed on the label of the filter. There should also be a serial number associated with the product since testing should have been done to make sure it actually performs at the level being claimed.

If you are looking to buy a true HEPA filter, you will want to avoid any product that says “HEPA-type” since they usually only made to look like HEPA filters but typically only capture 85-90% of particles. Another good rule of thumb is to avoid any so-called HEPA filters that appear to be priced ridiculously cheap compared to other brands.

Which Brand Has the Best HEPA Filter?

The brand name is less important than the labeling. Look for brands that say true or absolute. You may also want to learn about the MERV rating system that is applied to filters. Sometimes products will use it instead of saying HEPA.

What Are the Limitations of a HEPA Filter?

While HEPA filters are very good at removing harmful particulates from the air, some harmful contaminants are actually not made up of particulate matter.

Here is a list of contaminants that HEPA filters may not be effective against:

  • Viruses: Beware of any filter that claims to protect against airborne viruses. The truth is, viruses are simply too small to be filtered from the air by all but the most expensive industrial filters.
  • Bacteria: Bacteria are typically big enough to be captured on the surface of a filter. The problem is that when they die, they release something called endotoxins which can cause health issues. This is why it’s important to replace filters regularly.
  • Mold: Similarly to bacteria, filters usually have to problem capturing mold spores. Unfortunately, they may continue to grow on the surface of the filter and even release new spores into the air after a while. I can’t stress enough how important it is to keep clean filters in every product.
  • Airborne Chemicals: While this might sound obvious I thought it was worth mentioning. Never rely on any particulate filter to be able to stop or remove any kind of chemical fumes or smoke. The particles are simply too small to be captured.

Related Questions

How much is a HEPA filter? HEPA air filter prices will vary depending on the type of product. However, you can expect to pay anywhere from 50% more up to 20 times more for a good quality HEPA filter. In the case of air filters, you really do get what you pay for.

How often should a HEPA filter be changed? Air filters should be evaluated every 60 to 90 days. If there are any noticeable signs of wear it’s probably a good idea to replace the filter.

Are HEPA filters washable? Some HEPA air filters are washable and can be reused multiple times before replacement. Make sure that you check the wear after each washing to make sure replacement isn’t warranted.

Do HEPA filters get rid of smells? HEPA filters do filter out gases or odors. However, many filters are designed with some type of carbon-based material that will work in tandem with the air filter in order to help remove some odors.

Do HEPA filters remove viruses? Viruses are too small to be captured by HEPA and almost all other types of filters. Only the most expensive industrial grade filters are rated to filter out viruses.

What is the origin of HEPA filters? During the Manhattan Project, HEPA filters were invented to trap airborne radioactive contaminants and particles. After the war, development of inexpensive filters began and in the 1960’s, the first HEPA air filter was patented.

Final Thoughts

Proactive people with bad allergies or asthma are always looking for ways to improve the air quality around them. Finding ways to filter the air inside a home or office are one big piece of the puzzle toward breathing cleaner air.

In my opinion, HEPA air filters are well worth the cost if they can only stop one bout of coughing, sneezing, and itchy/watery eyes a day. There is no way to put a price tag on comfort. Just make sure you are vigilant and get what you are actually paying for when purchasing a filter.

Attributions
Featured image: https://commons.wikimedia.org/wiki/File:Use_air_filters_(reusable).JPG

Jim James

Jim James spent most of his childhood outdoors fishing on lakes in his area. Due to his scouting background, he has always been interested in survival, camping, and the outdoors in general. Jim is a best-selling author and has a degree in History, Anthropology, and Music. He lives with his family in Charlotte, NC.

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