An in-depth look at filter misconceptions.

With so many different air purifiers flooding the market today, it can be hard to know which air purifier is the best at protecting you and your loved ones.

There are many common misconceptions with HEPA filtration and what it can do. Many people think that HEPA is the industry standard, but there are better options out there.

Let’s start by looking at the difference between HEPA, ULPA, and DFS filter efficiency

  • HEPA “High-Efficiency Particulate Air” – efficiency rating: 99.97% removal of airborne particles at 0.3 µm in size. (largest particle size)
  • ULPA “Ultra Low Particulate Air”- efficiency rating: 99.999% removal of airborne particles 0.1 µm in size
  • DFS “Electrically Enhanced/Stimulated Air Filtration” – efficiency rating: 99.99% removal of airborne particles at 0.007 µm in size (smallest particle size)

Table of contents

1. What is a HEPA filter?
2. Harmful pollutants that aren’t considered particulate matter
3. What is a ULPA filter?
4. HEPA and ULPA similarities and differences
5. What is DFS technology?
6. Lifespan of filters
7. Round-up: What is the most effective filter between HEPA, ULPA, and DFS? 

1. What are HEPA filters?

HEPA stands for “high-efficiency particulate air” (filter). A HEPA filter is a mesh-like sheet of dense interwoven synthetic or glass fibers. HEPA is theoretically supposed to capture particles down to 0.3 (µm). As air passes through the filter, large particles get trapped, but anything smaller than 0.3 (µm) can get through and released back out into the air. Many harmful pollutants like certain chemicals, bacteria, allergens, and airborne viruses are much smaller than 0.3(µm).

When was HEPA created?

HEPA was created by the Department of Energy in the 1940s. It was used in facilities containing nuclear materials. HEPA’s purpose was to help contain and prevent the spread of radioactive contaminants through the air. In the 1950’s it became commercialized and has been used in many different industries and products. Today, HEPA is a generic term people associate with any type of “high efficiency” filter, but this can be very misleading.

A common misconception people have with HEPA filters is any air filter with the name HEPA in it is the same. People need to watch out for air purifiers that use the terms “HEPA-type” or “HEPA-like”. These terms are misleading, and these devices likely cannot remove particles as small as a “True HEPA” filter. There is no standard set in place for “HEPA-like” and “HEPA-type” products so this should set off an alarm that these filters don’t meet HEPA standards.

Other common misconceptions with HEPA filters

It’s important to know that other types of harmful pollutants smaller than 0.3(µm) can pass through a HEPA filter that isn’t considered particulate matter. It is a common misconception that HEPA filters can capture and destroy everything.

2. Harmful pollutants that aren’t considered particulate matter

VOCs: Volatile Organic Compounds

  • VOCs are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term health effects. Concentrations of many VOCs can be up to 10x higher indoors than outdoors. VOCs are often components of petroleum fuels, hydraulic fluids, paint thinners, and other cleaning products that can be found in your home and workplace. Many of these VOCs compounds are small enough to pass through a HEPA filter back into the air.


  • Bacteria can grow and buildup on HEPA filters causing microorganisms to collect on the filter. This can be a breeding ground for Bacterial toxins, also known as endotoxins. Bacterial toxins can get released back into the air if they are small enough to pass through the filter. Some bacterial toxins have been linked to serious health problems like coronary artery disease, cystic fibrosis, and autoimmune diseases.


  • Although large mold spores can be caught by a HEPA filter, they also can live on the filter. This can cause the mold spored to gather, reproduce, and potentially get released back out into the air.


  • Viruses come in many different sizes and some are smaller than 03 (µm). Although true HEPA filters can capture some viruses depending on the size, they don’t necessarily destroy the virus once in the filter. This gives them the potential to escape back out into the air. In the past, some HEPA based filters marketed themselves as the industry standard and claimed to protect from viruses, even though some viruses could potentially pass through them. Long story short, they can’t claim this to be true anymore.

3. What are ULPA filters?

Another filter people often come across is a ULPA filter “Ultra Low Particulate Air (filter)”, which is commonly confused with a HEPA filter. ULPA filters claim to remove 99.999% at 0.1 (µm).

4. HEPA and ULPA similarities and differences

  • Both HEPA and ULPA filters are made up of similar materials that allow for air to pass through them and trap airborne particles.
  • Both filters have a similar, although slightly different construction, and the air filtration process is the same.
  • HEPA and ULPA filters generally cannot remove odors or gases from the air.
  • While ULPA filters tend to do better with smaller particles than HEPA filters, they restrict airflow which means they will give you fewer air changes per hour at a given pressure drop.

5. What is DFS technology?

DFS, or “electrically enhanced/stimulated air filtration” technology was developed through a U.S. military grant. It has been rigorously lab-tested and has proven to remove 99.99% at 0.007 (µm). DFS technology also guarantees greater lifetime performance.

How DFS technology works

How does DFS work?

  • Each unit is individually tested with a class 1 laser particle counter and is certified to exceed traditional HEPA filtration providing the highest level of ultrafine particle and virus removal.
  • The DFS high energy field creates a self‐contained, highly ionized state in the main filter that clusters ultrafine particles to make them larger, allowing the main filter to effectively capture ultrafine particles.
  • The DFS continually creates high energy exposure through the pleats and fibers of the main filter. This prevents organism growth in the main filter and prevents live organisms from escaping back into the air.

6. How long does each filter type last?

HEPA and ULPA filters

  • On average, these types of filters are recommended to be replaced every 3-6 months depending on the usage and the filter type. This can become costly when you’re constantly replacing your filters every few months.

DFS filters:

7. Round-Up: What is the most effective air filter between HEPA, ULPA, and DFS?


  • Sadly HEPA filters can’t capture every single VOC, bacteria, mold, and virus out there. Even though HEPA filters can capture some of these, they aren’t designed to destroy all of these contaminants in the filter. This gives them the potential to be released back into the air you breathe. HEPA filters also tend to have issues with leakage because they aren’t always constructed to be airtight.


  • ULPA filters really aren’t that much more effective than HEPA filters when you compare them side by side. ULPA filters can restrict airflow, come at a higher cost, and have a shorter life span. They also have a larger pressure drop resulting in fewer air changes per hour at a given pressure drop.


  • DFS technology has been proven to remove 99.99% of airborne particles down to 007 µm in size. This is smaller than both HEPA and ULPA filtration systems. Each DFS unit is individually tested to ensure that it is airtight and working 100% correctly. DFS filters are custom made to remove fumes, solvents, cleansers, and other VOCs. We designed our VOC granular material to maximize airflow for effective and efficient operation of the unit, unlike HEPA and ULPA filters.
  • DFS technology prohibits microbial growth. This means not only are the particles captured, but they also cannot live, grow, or reproduce inside the machine after they have been captured. They will not be released back into the air.
  • Each DFS unit is individually tested with a class 1 laser particle counter to guarantee better than HEPA efficiency before it is delivered to you. That means someone has personally tested your unit to make sure it meets our standards 100%.

Your Takeaways

In the end, any air purifier technology is better than no technology. But, for a number of reasons, we think that DFS is the most effective technology. DFS kills the smallest size particles, is the cheapest to maintain and each unit is individually tested for overall quality, giving you peace of mind that you are breathing the cleanest air possible.

ASHRAE guidelines have recommended installing the highest achievable MERV rated filter to best address the likelihood of airborne transmission of viruses. DFS technology achieves greater than MERV16 efficiency with the pressure drop of a MERV 8 and can be installed without major capital expenditure. It also has a substantially longer and higher performance life cycle.

The Environmental Protection Agency (EPA), recommends eliminating the source of pollution when possible. By using technology like DFS, you’re taking harmful particles out of the air and helping to reduce your risk of developing these long-term illnesses.

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