• 855-600-6653
Mold Inspection and Testing

What Is a True HEPA Filter?

If you're looking at air-conditioners, HVACs, and vacuum cleaners for your home, you're going to run into the term "HEPA" eventually. What is a HEPA filter, and how can it help me improve the air quality in my home?

There are also several other HEPA terms, such as "HEPA-like" and "HEPA-style." You'll also run into the term "True HEPA." What's the difference between all of these HEPA specifications?

This post unpacks everything you need to know about choosing the right HEPA filter for your needs.

What Is the HEPA Filtration Standard?

The term HEPA stands for "High-Efficiency Particulate Air." Scientists invented the HEPA filter standard in the 1940s as part of the Manhattan Project, the United States program to develop the first atomic bomb.

The HEPA standard comes in European and American versions, with European HEPA filters removing up to 85% of particulate matter from the air. True HEPA filters, the American standard, removes up to 99.97% of the particulate matter in the air.

A HEPA filter features design and construction with fine fibers that trap particles larger than 0.3-microns in size. The efficiency of the filter worsens as the particle size drops. For the rest of this article, we're going to work with the U.S. True HEPA standard.

Do Industrial HEPA Filters Require Certification?

The U.S. Department of Energy regulates the standard for industrial HEPA filters in the United States. Interestingly, the standard doesn't define the manufacturing process or the materials required in the construction of HEPA filters. The only requirement is that the filter traps 99.97% of all particles in the air.

It's also important to note that there are no defined standards for consumer HEPA filters. The standard with the DOE exists solely for military and government installations and projects. For example, government contractors must follow all guidelines for manufacturing and installation when servicing air systems on government property.

The contractor must prove that the HEPA filters they install meet the regulatory standard of removing 99.97% of particulate matter from the air and particles down to 0.3-microns in diameter. Other industrial applications for HEPA filters include hospitals, clean rooms, and other biologically sensitive areas and installations.

Do Consumer HEPA Filters Require Certification?

Manufacturers of consumer air purifying systems don't require any certification of HEPA filters used in their products. The DOE doesn't regulate the consumer market. Therefore, there is no way a manufacturer can get a seal of approval for their HEPA standard.

Therefore, it's challenging to check if the manufacturer is following HEPA best practices and if the filter is genuinely HEPA-capable. In essence, you need to trust that the manufacturer is selling you a top-quality product.

The Environmental Protection Agency (EPA) states that there is no widely accredited system for measuring consumer HEPA standards. Therefore, manufacturers of consumer air purification systems are unlikely to follow the same HEPA guidelines as industrial manufacturers. As a result, you can expect that your filter might not be a true HEPA model, even though the manufacturer says it is.

Understanding HEPA-Related Terms

The HEPA standard is a performance benchmark. However, some manufacturers use private laboratory services to test the filters for efficiency and efficacy at the consumer level. Underwriters Laboratories is a company that specializes in testing consumer HEPA filters.

U.L. has an independent set of requirements for consumer filters to meet before they can receive the U.L. stamp of approval. When you're looking for a new air purifier system, always ensure it has the U.L. logo on the box; it's the only way you can be certain you're getting a genuine HEPA filter with the system.

There are several HEPA categories for consumer filters. However, just because they include the word HEPA in the product description doesn't mean it meets these standards. There is some clever marketing jargon that might confuse you when you're making your purchase.

Let's unpack these terms to give you a better understanding of consumer HEPA products and their classification.


As mentioned, True HEPA is the benchmark standard for these filters. True HEPA filters remove up to 99.97% of particulate matter from the air. True HEPA filters are suitable for people with allergies, as the filter removes the highest quantity of particulate matter from the air.


The HEPA-Type classification is just a marketing term; it means nothing and doesn't represent any manufacturing standard. The filter could be as effective as a HEPA model, or it might not be as good; it's hard to tell.

It's a good idea to avoid these cheaper filters and stick with a True HEPA model, especially if you suffer from allergies.


This jargon is another version of the HEPA-like term, and you should avoid purchasing these filters. Look for models that have the HEPA UL certification instead.


The Ultra-HEPA standard removes particulate matter down to 0.12-microns in diameter. These systems are expensive, and you'll find them in medical settings like doctors' rooms, hospitals, and operating rooms.

However, the high cost of these filters means that you won't find them in consumer products, and if you do, they are notoriously expensive.

Absolute HEPA

This term is the same as True HEPA, with filters offering better filtration power, removing up to 99.99% of all airborne particulate matter. You'll often find this term on vacuum cleaner filters.

Permanent HEPA

These HEPA filters meet the HEPA standard of removing 99.97% of all particulate matter from the air. However, they are reusable, allowing washing to clean the filter.

However, research shows that washing a HEPA filter reduces the efficacy of the fibers at catching particulate matter. Therefore, we advise you avoid using washable HEPA filters.

Activated Carbon Hybrid HEPA Filters

These filters combine activated charcoal with a HEPA filter for superior air cleaning. The activated charcoal scrubs odors out of the air before sending it through the HEPA filter.

This model is a great choice for use in areas where high levels of volatile organic chemicals (VOCs) are present. However, the carbon filter doesn't add to the HEPA standard.

Understanding HEPA-Related Marketing Terms

After reading through the standards, you can see that only the True HEPA rating is worth anything. The other HEPA rating doesn't guarantee the efficacy of the filter. If you're purchasing a consumer product, always look for the U.L. logo for confirmation that the product meets these HEPA standards.

If you're purchasing a filter system for a commercial purpose, always use True HEPA filters, and make sure you're using certified products for your installation.

If consumer products don't have the U.L. certification, you're taking a chance, and you could end up with a filter that doesn't meet True HEPA standards. Any other HEPA labeling on products is purely for marketing purposes only.

When searching for your new HEPA filter, make sure you look for models that feature the phrase "99.97% of all particles at 0.3-microns diameter." To evade and trick the consumer's awareness, many brands use clever marketing terms like "removes up to 99% of pollen and dust." The language may seem appealing, but you can bet that the filter doesn't meet HEPA standards or remove that quantity of particulate matter from the air.

If you ever see filters claiming to be better than the True HEPA standard, be cautious and avoid those products. There are a few other important terms to understand before you head out and purchase your new air purification system.


This acronym stands for "Clean Air Delivery Rate." It's a measurement of how much air flows through the filter.

However, it's not a reliable figure, and filters that don't sit properly in the housing may cause air to flow around the filter instead of through it. As a result, the filter will have a high CADR rating, but it might not be effective at cleaning the air.

Particle Size

Look for language on products stating "removes particles down to…." This specification is a clever play on words, but it doesn't mean that the filter performs as advertised. Without any specific data attached to the claim, it isn't very helpful.

There are Many Definitions of HEPA

As you can see, there are several definitions of the HEPA standard. Not all of them mean the same thing, and some are downright deceptive with the language they use in marketing materials.

In Closing – Check the Air Quality in Your Home with MI&T

If you have allergies, then several particles can cause allergy attacks. Mold, pollen, and dust are three common allergens causing allergic responses in sensitive individuals.

While a HEPA filter will help to remove dust and mold spores from the air, it won't stop the source of the mold from growing.

MI&T is the mold detection specialist. They'll visit your home and find the mold using specialized equipment. While they can't remove the mold for you, they can recommend best practices for doing it yourself.

After removing the mold, installing a HEPA filter in your air-conditioning system or HVAC helps remove any airborne particles spread during the cleanup. Contact MI&T today and book your detection service.