Are HEPA Filters Safe?

If you work in a lab, hospital or pharmacy, then you are likely surrounded by HEPA filters every day without knowing it. Read on to learn how HEPA filters keep you safe.

What Are HEPA Filters?

HEPA stands for high efficiency particulate air. According to the EPA, this type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria. It can also remove any airborne particles with a size of 0.3 microns or larger.

An illustration of a air and particles flowing through a HEPA filter

In order to filter the air effectively these filters are often made from polypropylene (or fiberglass). This is also often the reason why the question “are HEPA filters safe?” comes up. Concerns over fibers from the filter being blown into the air and inhaled into the lungs often drives this conversation.

Are Fiberglass Particles Blown Downstream?

So how many of these fibers are able to be blown downstream? Luckily a group of scientists tested just how many fiberglass particles are shed from HEPA filters. One test monitored the effects of long-term commercial installs and the other measured the effect of fiber shedding in controlled laboratory conditions.

“Test results showed that all media evaluated shed a minimal amount of fiber with some of the fibers being respirable. These results showed shedding was negligible compared to the number of fibers and/or particulate present in ambient air.“

So what does this mean? Ultimately, even though these filters do shed fibers, the World Health Organization says the low volume is not a cause for concern. In fact, HEPA filters would need to release 1000 times more particles before they would even be on their radar. The group of scientists also found one other interesting piece of information while performing the study. Over time the number of particles shed off of HEPA filters decreases.

Can Fiberglass In The Lungs Cause Problems?

The argument for HEPA filter safety is based on fiber glass creating health issues. So, lets look at how fiber glass exposure effects the human body. In the short term, if you are exposed to a lot of fiber glass particles you may experience an irritation of lungs. This may aggravate asthma and bronchitis, however, symptoms will subside however when exposure is decreased. For this to occur however, you would need to be exposed to significantly more fiberglass than is released from a HEPA filter.

computer generated image of man's body showing is lungs highlighted in red

Over the long term a number of studies have been completed to analyze the effects of fiberglass inhalation on the lungs. the National Academy of Science concluded that glass fibers do not appear to increase the risk of respiratory system cancer. This conclusion was mirrored by Canada’s Agency for Toxic Substances and Disease Registry (“ATSDR”) a few years later. In 2001, the International Agency for Research on Cancer changed the classification of “insulation glass wool”. Moving it from Group 2B (possibly carcinogenic) to Group 3 (not classifiable as to its carcinogenicity to humans).

Other studies have shown that fiberglass can be an irritant to the lungs over the short term. These same studies however show that this irritation is unlikely to have any long-term effects.

Are HEPA Filters Safe?

While HEPA filters do release a very small number of fiberglass particles into the air, their overall effect on the human body is negligible. This already slow rate of release, also decreases over time as the filter ages. Ultimatly, the quantity of particles a HEPA filter releases are no more harmful than the dust in the air. So, the next time you hear someone ask “are HEPA filters safe?”, you can confidently explain that they are.

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Frequently Asked Questions

How Frequently Do HEPA Filters Need To Be Changed?

Due to the high cost associated with HEPA Filters, many companies opt to have prefilters installed to extend the life of there HEPA filters. These prefilters are changed out on an annual basis. This can however, extend the life of the HEPA filter up to 5 years in some cases. When prefilters are not installed, however, HEPA filters should generally be changed once a year. This prevents the buildup of dirt and contaminants in the filters. Since HEPA filters are thick in frame, they can impede airflow in HVAC systems. This can result in inconvenient breakdowns or malfunctions if they are not properly maintained.

When filters are changed out, the old filters are decontaminated, bagged, sent to biowaste and destroyed.


ASHRAE’s Epidemic Task Force recently released a 41-page Article to help educational buildings resume occupancy during Covid-19. ASHRAE’s report is for educational facilities, but it can apply to commercial buildings as well.

The updated guidelines recommend using the highest MERV filter possible that your HVAC equipment will allow. We recommend you use a HEPA or MERV 13 filter. If your system can handle the pressure drop then a MERV 14 is preferred. An increase in filtration will result in a loss of capacity. To address this, use portable electric heaters in the winter and lower AHU discharge temps in the summer. The guidelines also recommend introducing portable HEPA/UV Machines in classrooms that have a minimum of 2 air rotations/hr.


Still worried about indoor air quality. Here are a few more ways you can reduce mold, bacteria, and viruses. While there are several types of air cleaning systems out there, two common ones are UV Systems and Bi-Polar Ionization Systems.


UV Systems can help people who suffer with allergies and also help prevent bacteria from causing issues in the workplace. They work by installing a high-powered UV light inside the duct system. As air passes through the ducts, the UV light kills the mold spores and bacteria. This has a direct impact on indoor air quality and is a viable option for some businesses.


These systems come into contact with the air in your HVAC system and can kill mold, bacteria and viruses just like a UV system. The ions these devices release cause particles in the air to bunch together which makes them stick to your filter. These ions can also remove the hydrogen atoms from viruses’, bacteria and mold which results in the death of these pathogens.

An interesting video showing how this type of system works can be seen here. This system can be a great alternative to UV System. It can also generally come in at a lower price point.