Clearing the Air: Air Quality & Management for Dental Offices & Labs

A mix of informative solutions and articles; this blog is focused on providing information about the science and containment of airborne hazards and health for dental staff.

Blog By:
Vaniman

How does HEPA filtration work?

HEPA stands for High Efficiency Particulate Air and is a filtration rating that captures microbes, dust, and particulates down to 0.3 Micron.

 But what does that really mean and how do they work?

The U.S. Department of Energy first termed HEPA as a filtering specification for suppliers of filtration products based on how effective they were at particle removal.

HEPA filters consist of a complicated mix of filaments and fibers that carry a static charge which lures various microbes and particles like a magnet. 

While the particles travel through the air filtration system, they’re captured and retained within the filter. Additionally, an interesting scientific effect occurs known as Brownian Motion which causes particles in certain media states (such as fluid) to bounce around and become trapped. 

How do N95 or KN95 face masks compare to HEPA air purifiers?

You may see or hear about people wearing surgical masks or N95 or KN95 rated masks to prevent themselves and others from being exposed to Covid-19.  One important thing to note is that these masks are not as effective as HEPA air purifier systems.

N95 or KN95 face masks capture 95% of particles down to 0.3 micron. This means that 5% still get through the protection. HEPA air purifiers in contrast are 99.97% effective at 0.3 Micron and are much more efficient than face masks.

What is the difference between MERV and HEPA filters?

You may have heard the term “MERV” before. It stands for Minimum Efficiency Reporting Value and is a rating system for HVAC air filters created by the American Society of Heating, Refrigerating, and Air Conditioning Engineers or (ASHRAE). 

Many people are asking the question, “can I use a MERV filter in a mask”?

While there have been no scientific studies we could find for this, the answer is likely no. 

Here’s why…

MERV stands for Minimum Efficiency Reporting Values, or MERVs, report a filter’s ability to capture larger particles between 0.3 and 10 microns (µm). (Per the EPA)

HEPA and MERV filters are usually not the same.  MERV rated filters are typically used in air conditioning systems, including systems found in most homes. 

MERV filters have a rating system… MERV 7, 8, 10, and so on—up to MERV 20. 

MERV filters are not effective at filtering microbes and viruses until they are rated at 17 or better. 

At these ratings, these are considered HEPA or ULPA rated and are effective, however you likely won’t see the MERV rating in these applications as they would simply state “HEPA” instead.

How do viruses like COVID-19 spread through the air?

By nature, viruses are sub-micron in size-we’re talking 500nm (0.5 micron) and below.  Not to mention viruses only require a small amount to enter your body in order to start an infection.  

The sad truth is that some viruses will inevitably pass through any HEPA filter.

Here’s why…

Typically, viruses like COVID-19 or even H1N1 are spread through the air via biological aerosols.  These tiny moisture droplets are expelled whenever you sneeze, cough, or go ACHEW!

They carry bacteria and viruses through the air and ultimately your respiratory system.  

Overtime, with enough volume or use, particles will eventually separate and penetrate the filter due to their sub-micron size.

How can a HEPA air purifier help lower the spread of the COVID-19 virus?

Research studies have been conducted to test the efficacy of HEPA filtration on moisture droplets containing viruses.  This was due to the potential of using pathogens as biological weapons.

Most biological aerosols range in sizes from 0.5-3 micron. HEPA air purifiers captures aerosol particles in that size range 

On paper, it is impossible for any HEPA filter to be 100% effective since many microbes are less than 0.03 micron in size—but that’s in an isolated form where they typically can’t survive long.

Plus, research is still being done on the subject.

An interesting study performed by NASA indicated that HEPA filters were able to capture sub-micron particulate down to 0.1 micron!

You can view the study here: NASA HEPA Study

Additionally, all testing is performed using brand new filters. HEPA filters actually work better the “dirtier” they get (up to the point where airflow is restricted).

This makes it a viable option for capturing aerosol particles.