If you’ve been thinking about purchasing an air purifier you’ve probably noticed manufacturers throw the term HEPA around a lot. A HEPA filter is a filter used inside many air purifiers. 

HEPA is an acronym for High-Efficiency Particulate Air. Essentially, it traps smaller particles than your typical filter – as small as 3 microns.

You’re told that a purifier is better because it has one of these filters. Is that true? And just what is a HEPA filter? You’ll find all of the answers you’re looking for below.

How does a HEPA Filter Work?

A HEPA filter has tiny twisted glass fibers packed together tightly, making it hard for small particles to get through. As the air flows over the filter, a HEPA filter catches up to 99.97 percent of particles in the air mixture on its fibrous surface. 

A HEPA filter’s purpose is to clean the air we breathe. We take in a ton of potentially harmful microscopic particles every time we breathe in. The HEPA filter captures 99.97 percent of them before they get into our lungs.

The HEPA filter captures particles in three different ways:

In the first method, when particles catch the side of the filter and stick to it this is called interception.

The second process is impaction – this is when particles make a direct impact with the filter, stopping their forward progress.

The third and final way these filters can capture small particles is by diffusion. This is when the particles interact with gases flowing through the filter. It slows them down, causing them to entangle in the filter.

What Problems can HEPA Filters Help Solve?

HEPA filters can help solve a range of health problems. They do a great job of capturing pet dander, pollen and, dust. That makes them the perfect tool for making your home less allergenic. 

For anyone that suffers from daily allergies, these filters can feel like a “life saver” – at least when we’re in our own homes. 

A HEPA filter can’t cure lung disease, but it can help to prevent further health problems that can make things worse.

Manufacturers use HEPA filters in a range of industrial applications – including the nuclear industry, where they help to prevent the spread of radioactive particles.

While they aren’t designed to specifically capture odors, some of the particles they remove from the air, such as mold, have a distinctly unpleasant smell. Removing them from the air removes their odor as well.

Types of HEPA Filters

Things get tricky when we start looking at the different types of HEPA filters. Intuitively we would think one HEPA filter is no different from another.

Not so fast. It turns out that Americans and Europeans have different standards when it comes to defining a HEPA filter – American standards are much more rigid. In Europe, a filter only has to capture 99.95 percent of particles 3 microns or larger to be labeled a HEPA filter, compared to American standards which call for 99.97 percent.

The other problem is many companies are advertising “HEPA-Type” filters that aren’t HEPA at all. It can be hard to make sense of it all. Read on and things will become a lot clearer.

What’s the Difference between HEPA Filters and True HEPA Filters?

Is there a difference between a HEPA and a True HEPA filter? The short answer is no. Some manufacturers have started to use the term True HEPA to indicate that their product complies with the actual HEPA standard. 

A HEPA filter and a True HEPA filter both meet the standard set by the United States Department of Energy. Unfortunately, some products use HEPA in their marketing campaigns, that aren’t HEPA at all. True HEPA, is the new term used to confirm that a product has a filter that meets the official definition.

What’s the Difference between True HEPA Filters and HEPA-Type Filters?

What about HEPA Type filters? They’re the reason that manufacturers have created the term True HEPA to indicate a HEPA compliant product. HEPA Type filters aren’t actually HEPA at all. 

Just to recap, a HEPA filter captures 99.97 percent of particles that are 3 microns or larger. That means that out of every 10,000 particles of this size that contact the filter, only 3 get through. A HEPA Type filter may capture somewhere between 85 and 99 percent of particles that are 2 microns or larger. There’s no set standard for these products.

How do HEPA Filters compare to Other Types of filters?

Microfiltration vs HEPA Filtering – Microfiltration systems offer comparable results to HEPA filters, but the process is quite different. Microfiltration uses multiple layers of filters. The first layer is a 1 ply cellulose filter media that captures large particles of dirt and the second layer is a polypropylene melt-blown filter that captures the smaller particles the first layer missed.

Microfiltration will capture between 90 and 98 percent of particles, depending on the quality of the filter.

Ion Filters vs HEPA FiltersIon air purifiers are quite different from HEPA based products. They work by releasing electrically charged ions into the air around them. These charged ions bond with unwanted particles making them heavier than the air. The particles then drop to the ground, or on nearby surfaces so that we don’t breathe them in. 

The problem is that these particles aren’t captured, so they can be kicked back up into the air when someone walks through the room.

Particles may also accumulate on walls and furniture creating black spots. These aren’t just unpleasant to look at, they may also be harmful to your health.

Electrostatic Filters vs HEPA Filters – Air purifiers with Electrostatic filters charge the particles in the air, similar to an ozone filter. The difference is these purifiers then filter the particles and collect them on a plate which needs to be removed and washed periodically.

EPA Filters vs HEPA Filters  – EPA filters can vary a lot in their effectiveness. They capture between 85 percent and 99.5 percent of small particles. Even on the upper end of the scale, they are not as effective as HEPA filters.

Carbon Filters vs HEPA Filters – HEPA filters and carbon filters do different things. As we’ve already covered, HEPA filters remove particles as small as 3 microns with 99.97 percent efficiency.

Carbon filters capture odors, smoke, and chemicals from the air in highly absorbent carbon pores which open up when in contact with oxygen, trapping these particles inside. They’re common in industrial settings, but they are often used in coffee makers as well as a purifier to remove any impurities and improve the taste.

HEPA Filters FAQs

Will a HEPA filter catch asbestos?

Older homes may still have some undiscovered asbestos. If this is a possibility, HEPA filters are a great way to protect your family. Asbestos particles are about 0.7 microns in size, much larger than the 3-micron threshold associated with HEPA filters, that’s why HEPA filters are highly effective at removing them from the air we breathe.

Are HEPA filters washable?

It depends. There are both washable and non-reusable HEPA filters –
at least according to some manufacturers. The truth is that even washable filters lose effectiveness over time. Be sure to check your product’s documentation to ensure your filter is washable. The best solution is to buy a new filter.

How often should you change a HEPA filter in an air purifier?

HEPA filters are a great tool in your war chest in the never-ending battle against allergens and other potential health problems. They don’t last forever though. Over time, they can lose their effectiveness and mold may even begin to grow and thrive on them. To prevent this, change the filter every 3 to 4 months.  

Be careful though, some HEPA filter replacements can be quite expensive — prices can range between $50 and $200. You’ll want to clarify what the replacement costs are before making a purchase. Also, be sure to make sure you are purchasing an actual HEPA or True Hepa filter.

Why is the standard HEPA filter size 0.3 microns?

When we reduce the particle size that a filter can capture, it becomes harder for the air to pass through the filter. By settling on 0.3 microns, we capture many contaminants, such as dust, pollen and pet dander. 

Fungi and viruses are smaller than 0.3 microns, so it’s important to keep in mind that HEPA air purifiers will not be effective at removing them from the air. Some high-end air purifiers also have built-in UV technology. This UV light can help to reduce germs and viruses in the air.

A Good Investment

Air purifiers with HEPA filters (or true HEPA filters) are a little more costly than similar products and are also more expensive to replace. There’s a simple reason for this and that’s because they work. You can save money by choosing an air purifier that uses a “HEPA Type” product, but you’ll also be leaving a lot of the contaminants in the air you’re trying to remove. A True HEPA air purifier is a good investment.