Different HEPA Filter Types & How to Choose

It’s important to understand HEPA filters if you want to keep the air in your facility safe.

The U.S. HEPA standard requires that a filter retain 99.97% of particles 0.3 μm (micrometers, or microns) in diameter (the European standard is 99.95%), while particles both smaller and larger are filtered out at even higher efficiency. To give you an idea of how tiny 0.3 micrometers are, anything smaller than about 50 μm is invisible to the naked eye. 

Ideally, every HEPA filter would be undamaged when installed and allow no air to bypass its seals, operating perfectly until needing replacement, which is done faithfully every 6 to 12 months (or as appropriate given usage, prefilters, etc.). 

With such a straightforward and clear explanation of HEPA filters, why do we hear about HEPA filter types (even though there is only one), and why is it necessary to look for HEPA equipment certifications to ensure they're the real deal?

What You Need to Know About Modern HEPA Filters

True HEPA filters, or high-efficiency particulate air, filters are considered the gold standard in air filtration within the healthcare industry for good reason. These filters are highly regarded because of their powerful ability to remove 99.97% of airborne particles as small as 0.3 micrometers in diameter. This exceptional filtration efficiency is life-saving in healthcare settings, where maintaining clean air is imperative to patient safety and infection control. HEPA filters are most commonly used in hospital isolation rooms, operating rooms, and laboratories to ensure that the air is free from harmful contaminants, including bacteria, viruses, and other pathogens that can irritate sensitive patients or contribute to the spread of infection and disease. The types of HEPA filters vary based on the specific needs of different industries, such as healthcare, aerospace, and pharmaceuticals.

Falsely Advertising Types of HEPA Filters 

Not all products labeled as "HEPA" actually meet the rigorous standards required to be considered genuine HEPA filters. Don’t let the marketing jargon confuse you — efficient particulate air filters can only be classified as true HEPA filters if they meet specific efficiency criteria, capturing at least 99.97% of particles that are 0.3 micrometers in diameter. Many products on the market use terms like "HEPA-type," "HEPA-like," or "HEPA-style," which are misleading and do not meet the same efficiency standards as the certified HEPA filter meaning.

A filter is either rated as HEPA-certified or it is not. There is no in-between. 

Other non-HEPA efficiency air filters may provide some level of air purification, but they fall short of the performance of true HEPA filters, compromising air quality in critical environments like emergency rooms, isolation spaces, and operating rooms. When it comes down to it, don’t leave the health of your facility up to “HEPA-style” filtration. It’s essential to look for certifications and ensure that the filter you choose is a true HEPA filter or medical-grade HEPA filter to ensure optimal performance and the ultimate level of protection against infection and disease.

HEPA Filters Undergo Rigorous Performace Testing

In order to differentiate real HEPA pleated mechanical air filters and ensure their quality of performance, all filters sold under the HEPA meaning must be rigorously tested. Independent labs test the filtration capabilities of each filter using standards as set forth by organizations like the Institute of Environmental Sciences and Technologies (IEST) and Underwriters Laboratories (UL). These tests involve passing regulated chemical aerosols through the filter to ensure that the proper amount, at least 99.97% of all particles that measure .03 microns, are captured. The data from this type of testing is then printed on a label that is affixed to the efficiency air filters themselves.

Why “In Situ” HEPA Filter Testing is Important 

Even with a properly tested HEPA filter, you need reassurance that the filter will perform properly “in situ” (as installed) — and that means testing it in place. The main issue is that the machinery surrounding the filter must be properly designed and manufactured to prevent leakage past the filter. Since filters can get damaged in transit, testing in place also ensures no pinhole leaks in the filter itself.

Here’s another way of explaining the importance of in-situ testing from the National Air Filtration Association: A HEPA filter is only as good as its gasketing and framing when installed, and because all HEPA filters are used in critical applications, in-place HEPA filter testing should be mandatory. This testing ensures that 100% of the air entering the unit passes through the efficiency air filters by revealing any leaks in seals, ductwork, or filter.

The Origin of Today’s HEPA Filter

An urgent need for effective filtration arose from the use of poison gas in warfare. During World War II, the British found that a paper filter element from a captured German gas mask was remarkably efficient at capturing chemical smoke, and the British Army Chemical Corps replicated it for use in their own gas masks. Before long, they developed an air purifier with a blower and a deeply pleated cellulose-asbestos paper filter. This so-called "absolute" filter laid the groundwork for the HEPA filter.

The U.S. Army Chemical Corps and the National Defense Research Committee built on the British research to develop the HEPA filter, identifying as their target the 0.3 μm size, which they called the "most penetrating" size, to remove radioactive particles from the air during the Manhattan Project.

After the war, HEPA became a registered trademark (and later a generic trademark meaning "highly efficient filter"), and commercial applications spread rapidly, serving healthcare, high technology, aerospace, pharmaceutical, and other industries.

How HEPA Filtration Works

HEPA filters are highly efficient at trapping particles of various sizes, thanks to their intricate design and the multiple mechanisms they use to capture contaminants. These filters are pleated mechanical air filters, meaning they use pleated sheets of filter media to create a maze that particles must navigate, making them ideal for capturing small particles in the air. 

HEPA filtration works by combining the effectiveness of three methods: 

1. Impaction: Larger particles in the air tend to move in a straight path and can collide directly with the filter fibers. This process, known as impaction, acts like a sticky trap. The fibers often have adhesive properties that ensure these particles remain stuck and cannot pass through the filter.
2. Interception: As airborne particles navigate through the filter, they may come close enough to the fibers to get caught. This interception process is akin to particles getting tangled in a maze, making it impossible for them to bypass the filter.
3. Diffusion: Diffusion is particularly effective for capturing the smallest particles, those smaller than 0.3 micrometers. These tiny particles move erratically due to Brownian motion, a random zig-zag movement caused by collisions with gas molecules. This unpredictable motion increases the likelihood that the particles will collide with and get trapped in the filter's fibrous maze.

This combination of filtering mechanisms makes true filter type HEPA filters, including heavier-duty medical-grade HEPA filters, highly effective in environments where air purity is critical, such as healthcare facilities. 

Applications of HEPA Filters 

HEPA filters are not one-size-fits-all. While there is only one degree of being a HEPA filter or not, various industries may use them in different ways to best support their infection control strategies. 

HEPA Filtration for the Healthcare Industry

In healthcare settings, maintaining clean air is vital for patient safety and infection control. True HEPA filters are a foundational element of a powerful infection control strategy, especially in critical areas like operating rooms, isolation rooms, and intensive care units. Medical-grade HEPA filter rating products are rigorously tested to ensure they meet healthcare standards and are often paired with advanced technologies, such as UV-C light, to further reduce disease-causing pathogens. Understanding HEPA filter meaning and HEPA filter rating is crucial when selecting the right filtration system for healthcare environments that will support a safe and healthy medical environment. 

Types of HEPA Filters Used in the Pharmaceutical Industry

In pharmaceutical settings, HEPA filters are used to create controlled environments essential for drug manufacturing and research. These filters ensure that the air is free from contaminants that could compromise the integrity of pharmaceutical products. Filters used in this industry are often designed to meet stringent standards and are regularly tested to ensure they maintain their efficiency over time.

HEPA Filter Types in Various Industries

Beyond pharmaceuticals, various HEPA filter types are widely used in healthcare, aerospace, high technology, and other industries where air quality is critical. In healthcare, for example, true HEPA filters are essential in preventing the spread of airborne infections, while in aerospace, they help maintain air purity in enclosed environments like spacecraft.

Discover the Importance of Choosing the Right HEPA Filter

Selecting the right HEPA filter is crucial for ensuring that the filter matches the specific needs of your environment. The type of HEPA filter you choose should align with the application, whether it’s for healthcare, pharmaceuticals, or any other industry where air purity is vital. Factors such as filter efficiency, size, and the environment where the filter will be used all play a role in determining the best filter for the job. Using the correct filter ensures that your air filtration system operates at peak efficiency, providing the highest level of protection against airborne contaminants.

HEPACART® Medical-Grade HEPA Filter Equipment

Selecting the right HEPA filtration equipment for your facility is crucial for maintaining clean air and ensuring the safety and health of everyone within the space. Our HEPA-filtered equipment includes the HEPACART mobile dust containment carts, HEPAFORCE® AIR Negative Air Machines, and HEPAFORCE GermBuster Room Air Purifiers.

HEPACART Dust Containment Carts

HEPACART Classic

Designed with healthcare in mind but versatile enough for construction, the HEPACART Classic features a medical-grade HEPA filter with a MERV rating of 18, capable of removing 99.97% of particulate matter down to 0.3 micrometers. Available in three sizes — Classic 55, Classic 74, and Classic 74X  — this mobile containment and filtration system ensures your facility is protected from harmful airborne contaminants.

HEPACART AutoLift

For facilities requiring efficiency and ease of use, the HEPACART AutoLift offers all the benefits of the HEPACART Classic with the added convenience of an electric push button for easy height adjustment. This unit can reach up to 10 ft. 6 in. and includes the HEPAFORCE AIR Negative Air Machine & Scrubber, making it ideal for rapid deployment in healthcare or construction settings whenever you need dust containment on the go. 

HEPAFORCE GermBuster

In medical facilities, preventing the spread of infection is critical. The GermBuster air purification machine continuously filters and disinfects the air, capable of purifying a 3,200 cubic foot room six times per hour. It uses a HEPA filter to remove contaminants and can be enhanced with UV-FORCE technology to further destroy bacteria, viruses, and spores.

Create Healthier Indoor Air With HEPACART

At HEPACART, we proudly offer a wide range of equipment that you can trust to provide medical-grade HEPA filtration, meaning they have the highest efficiency rating, making them ideal for hospitals and outpatient facilities where health and safety are non-negotiable. 

Learn how the effectiveness of a HEPA filter paired with the power to intake contaminated air can create an environment with safe and clean air for any industry. Explore our air change calculator today to help you understand the type of equipment that will empower the level of indoor air quality you’re looking for and inform your equipment purchasing decision.