As the pandemic continues to evolve, we take a look at HEPA. Why it’s so effective at removing viruses such as Covid-19 from the environment. And why the CDC recommends the use of HEPA air filtration in a variety of settings.
How does HEPA capture viruses such as Covid-19 that are smaller than 0.3 microns?
When discussing HEPA, we often talk about its ability to capture particles that are 0.3 microns in size. Why particles of this size specifically? This may come as a surprise but particles that are 0.3 microns in size are more difficult to capture than smaller particles, such as Covid-19. This is due to something known as the ‘Brownian Motion’. Smaller particles flow in a zig zag motion, this movement makes it easier for them to be captured by the HEPA filter.
Why does the CDC recommend using HEPA air filtration?
In the early stages of the pandemic, the main method of transmission was thought to be via droplets. That’s large particles of saliva that fall onto surfaces when a person coughs or sneezes. When we touch the same surface and then our face, specifically our mouth, eyes and nose, we can become infected.
However in July 2020, the WHO confirmed the risk of airborne transmission for the Covid-19 virus is much higher than previously thought. When a person talks, coughs or even breathes, they send tiny particles of respiratory droplets, known as aerosols, into the surrounding air. These particles are so tiny, they can hang around in the air for hours, long after the infected person leaves the area.
As well as maintaining a distance, hand washing, regular cleaning of surfaces and the use of masks to slow the spread, the CDC also recommends increasing ventilation in indoor spaces and the use of air filtration to reduce airborne exposure. This is known as a layered strategy that, if implemented together, will help to reduce the risk of infection.
Why does the CDC recommend air filtration in schools?
Schools are the perfect environment for airborne viruses to spread. Large groups of people remain indoors for prolonged periods of time, often in small spaces with little or no ventilation. We know from experience that the cold and flu viruses can infect a whole classroom in a very short period of time. And as there is evidence to suggest Covid-19 is more infectious than influenza, it is fair to assume a classroom of children can contract the virus very quickly, if safety measures are not put in place.
Opening a window and using fans helps to improve ventilation in a classroom but opening a window is not always an option, particularly in the winter months. And although ventilation helps to circulate the air, it does not remove contaminants in the way that HEPA filtration does. Using HEPA will significantly reduce the number of viral particles in a classroom environment and therefore minimize the risk of transmission.
Why do we need to use HEPA in the work environment?
In the same way that the CDC recommends the use of HEPA filtration in schools, they also advise it’s use in offices and workspaces too. The office environment can be difficult to ventilate, modern buildings are often sealed shut, with no option to open a window. And older buildings, with outdated HVAC systems do not provide adequate ventilation or filtration. Using a portable HEPA air purifier is a cost-effective way to ensure contaminants are removed from the air.
Why does the CDC recommend air filtration during dentist’s procedures?
Like schools, dental procedures are high risk environments for transmission. Patients cannot wear a face covering throughout and dentists cannot maintain a distance when working on a patient. Some procedures such as high-speed drilling and ultrasonic cleaning create large amounts of aerosolized droplets in the environment. Using effective HEPA filtration helps to reduce aerosol concentrations in a room and also increases the effectiveness of the turnaround time between patients.
Why do healthcare settings need HEPA air filtration?
When we talk about healthcare settings, we tend to think of hospitals, with permanent air filtration systems installed. But there are many other healthcare settings, such as long-term acute care facilities, inpatient rehabilitation facilities, nursing homes and assisted living facilities, where HEPA air filtration is also recommended by the CDC.
In certain environments, such as nursing homes, it is not always possible to maintain a safe distance or wear a mask at all times. Portable HEPA air purifiers help to reduce the number of airborne contaminants, therefore protecting staff and patients.
Why HEPA makes it safe to fly?
Results of a study from the Department of Defense show that flying may be the safest way to travel during a pandemic. The Medical Grade HEPA filtration used on most aircraft ensures a regular exchange of air and therefore a very short lifespan for airborne particles, including the Covid-19 virus.
For the purposes of the study, sensors were installed throughout the cabin, to measure particles that were released every 2 to 4 minutes. Results show the particles were quickly diluted and only remained detectable in the cabin for around 6 minutes. In a typical American home it takes around 90 minutes to clear the same number of particles.
This study illustrates just how effective HEPA filtration is at removing contaminants from the air and how it may help to reduce the risk of transmission.
What’s the take-home on HEPA?
It is clear from the DOD and CDC data, HEPA filtration is highly effective at removing the very smallest of airborne particles. However it is worth remembering that it is just one tool in the CDC’s ‘mitigation toolbox’. Using HEPA air filtration alongside strict cleaning protocols, handwashing, keeping a distance and the wearing of masks will all help to reduce the risk of exposure to the virus. The more tools we use, the more protected we are.