These days we’re all looking for ways to keep ourselves, our families, and business premises safe from COVID-19. While masks and social distancing measures are critical to suppressing the spread of the novel coronavirus, can air filtering help keep us safer?
At Pro Housekeepers, we know that cleanliness is the most important thing on everyone’s minds right now, and we’ve been in the business of cleaning long enough to know a thing or two about what works and what doesn’t. That’s why we’ve put together this handy guide to explain how air filtration works, how effective it is against COVID-19, and what you can do to keep your premises safe.
Pro Tip: The science surrounding COVID-19 is evolving all the time, so be sure to check the CDC or other trusted source for the latest information and advice.
How is COVID-19 spread?
In order to understand which measures are most effective at reducing the spread of the coronavirus, it’s important to know how the virus is transmitted. SARS-CoV-2, the virus that causes COVID-19, is spread primarily through respiratory droplets — tiny particles of fluid that we produce whenever we breathe, talk, cough, or sneeze. The virus needs these droplets in order to remain active long enough to infect somebody else, which happens when they are inhaled.
Is COVID-19 airborne?
While there has been some debate in scientific communities about whether or not the coronavirus is airborne according to the strictest definition, evidence suggests that airborne transmission is possible. That’s because the only difference between a non-airborne virus contained in respiratory droplets, and an airborne virus, is how long those particles hang around in the air.
Larger particles are denser than air, and therefore fall quickly, making it unlikely that anyone else will breathe them in unless they’re standing very close to the infected person. That’s why social distancing and mask wearing are so important: masks contain some of the droplets that people exhale, and keeping a distance of six feet from others prevents walking through the droplets before they fall to the ground. However the only difference between these droplets and airborne particles is size. Once a droplet is small enough to be able to hang in the air for an extended period, then anybody passing through that place, even long after the original host has left, is at risk of contracting the virus. That makes air filters an attractive solution to preventing the spread of airborne infectious particles (also known as “aerosol”).
Does humidity affect the coronavirus?
A study from the University of Sydney and the Fudan University School of Public Health in Shanghai found that SARS-CoV-2 flourishes in low humidity. For every 1 percent reduction in relative humidity, the study estimated that COVID-19 cases increased by 7-8 percent. That means increasing the relative humidity by 10 percent could halve the infection rate. The reason humidity affects the virus is related to particle size — in low humidity, particles are smaller and can remain airborne longer, while high water content in the air binds to these particles and causes them to fall more quickly. Installing a humidifier in your home or business premises is therefore a good way to reduce the risk of airborne transmission.
Can HEPA filters stop COVID-19?
The virus itself is tiny, just .1 microns across, and HEPA (high-efficiency particulate air) filters only remove particles larger than .3 microns. That might suggest that traditional air filters aren’t fine enough to protect against COVID-19, but the virus itself requires the protective droplet in order to survive, and the entire particle is large enough to be contained within HEPA filters.
This is great news for businesses and homeowners, because it means HEPA filters are effective against the coronavirus, but only to a point. The filter must be securely attached to the air filtration system without any gaps, however tiny, through which the virus can escape. Regular filter changes are also required in order to ensure the same level of protection, and even under ideal circumstances, the EPA cautions that air filtration alone is not enough to combat the virus.
“When used properly, air cleaners and HVAC filters can help reduce airborne contaminants including viruses in a building or small space. By itself, air cleaning or filtration is not enough to protect people from exposure to the virus that causes COVID-19. When used along with other best practices recommended by CDC and others, filtration can be part of a plan to protect people indoors.” —EPA
How effective are air purifiers at protecting against the coronavirus?
Although air filtration is only one precaution that should be taken against the spread of COVID-19, it can be very effective when used correctly. In typical homes or small business premises, the air is fully circulated approximately once every two hours through small cracks around doors and windows, as well as through general use such as entering or exiting the building. With a portable air filtration machine, that process can be sped up dramatically.
CADR, or Clean Air Delivery Rate, is the metric air filters use to measure how fast air is circulated, and typically refers to the best performance the machine can produce on its highest setting. The rate is measured in cubic feet per minute, so a 250 CADR model will produce 250 cubic feet of clean air each minute. You may also see three different CADR rates displayed on a single machine — for smoke, dust, and pollen, which respectively refer to small, medium, and large particles. So a unit with a dust CADR of 300 will remove an equivalent amount of dust as if 300 cubic feet of clean air was added to the environment every minute.
For best results, experts advise looking for air purifiers with a CADR rating of at least 240, and as high as 300 for smoke/small particles in order to provide effective protection against COVID-19. Note that running an air filter on a lower setting will produce a less effective CADR, but high settings are often too noisy to be practical.
It may seem obvious, but air purifiers can only be effective while they’re running, so any protection you add to your property by installing a purifier will only last as long as the machine is switched on. If an office purifier is turned off overnight, there is potential for viral particles to remain in the air and still be present when the building reopens in the morning.
Which air filter is best for COVID-19?
The National Air Filtration Association (NAFA) further advises that low-efficiency filters (less than MERV 8) are unlikely to be effective against the coronavirus. Minimum Efficiency Reporting Value, or MERV, refers to the effectiveness of the filter at capturing various particle sizes. MERV ratings range from 1-20, with 1 providing the lowest level of filtration, and 20 the highest. At the top of the range, filters rated 16-20 are usually only found in specialist facilities such as hospitals, clean rooms, and power plants. MERV 5-13 are the most common filters available for residential and commercial use.
In order to be categorized as MERV 8 by NAFA, a filter must remove at least 70 percent of particles 3-10 micrometers in size, and 20 percent of 1-3 micrometer particles. This means an air filtration system using a MERV 8 filter will not be enough to eliminate smaller, aerosolized coronavirus particles, but many commercial filtration systems employ both a MERV 8+ filter and a HEPA filter, providing extra protection against airborne pathogens.
HEPA filters are not MERV rated, but are typically equivalent to MERV 17-20, at the very highest end of the MERV scale. They reliably capture up to 99.97 percent of particles greater than .3 microns, so provide the most protection from indoor air contamination. That means homes and businesses can get hospital-grade air filtration without the need for extensive HVAC upgrades.
The MERV Rating Scale
Particles 0.3 – 1 micrometers
Particles 1 – 3 micrometers
Particles 3 – 10 micrometers
< MERV 5
While it might seem the obvious choice to simply buy the highest-rated air filtration system available, there are downsides to consider other than the noise and the cost. Every filter, even MERV 1 filters, create pressure drops because they impede the flow of air through the unit. Air filtration pressure drops aren’t enough to make your ears pop, but they can force air to bypass the filter if it is not properly sealed. Installing a higher-rated filter into an air purifier than it was designed to house can create a pressure drop large enough to break the filter or even wear out the motor.
The higher the filter you use in your air purifier, the greater the pressure drop, and the more energy will be consumed forcing air through the filter. This can result in filters requiring replacement more frequently and the machine being louder and more expensive to run. Finding a balance between effectiveness and convenience will depend on the size and type of premises (offices will need to be quieter than workshops, for example), and ultimately the budget available to spend on an air purifier.
A final consideration is UV light. Light on the ultraviolet part of the spectrum has germicidal properties that can provide additional purification, helping to kill any pathogens that do make it through the filters. Many commercial air filtration systems contain UV-C germicidal bulbs that can add an additional layer of purification not only to the air, but to the filter itself. Whenever changing filters in air purifiers, it’s always best practice to assume they are contaminated and take appropriate precautions when removing them, such as wearing an N95 mask, disposing of filters in a sealed bag, wearing gloves, and washing your hands thoroughly afterward.
Air filtration specifications for COVID-19
When choosing the right portable air filtering device for a property, look for the following specifications:
- CADR of 240 or higher
- MERV 8+ pre-filter
- HEPA filter
- Internal UV-C germicidal bulb
Using air monitors in tandem with air purifiers
Even the most effective air filtration system will provide variable results depending on the settings used, the position and duration of use, and how frequently the filter is changed. Most systems monitor the pressure drop in order to determine when the filter needs to be replaced, but this is not always the most accurate indicator of how effectively the filter is working. Using an air monitoring system in tandem with an air purifier provides real-time insight into the condition of the air quality, and serves as an early warning sign that the filter should be changed.
Indoor air quality monitoring systems that claim to detect SARS-CoV-2 are beginning to emerge on the market, but even standard air testing equipment is useful for staying informed about the effectiveness of your air filtration and quality of indoor air. Historically, air monitoring for viruses has been uncommon because samples require Polymerase Chain Reaction (PCR) analysis in order to reproduce organic material to testable levels. This can be done quickly and effectively with machines in lab settings, but is beyond the reach of most commercial products.
Instead, indoor air quality sensors test the compositional makeup of the air (such as the levels of carbon dioxide, nitrogen dioxide, and carbon monoxide), the quantities of Total Volatile Organic Compounds (TVOCs), which can be emitted by paints, fabrics, varnishes, and cleaning solutions, and Particulate Matter (PM2.5), as well as ozone, temperature, and humidity.
Particulate Matter (PM2.5) is probably the most significant test result when determining if air filtration is effective against the spread of SARS-CoV-2, as this measures the concentration of airborne particles smaller than 2.5 micrometers that are present in the environment. As this is the size of most coronavirus-carrying respiratory droplets, a high PM2.5 reading suggests that current air purification methods would be ineffective if the SARS-CoV-2 virus was present on the premises.
How to maximize air purifier effectiveness to prevent COVID-19
Simply installing an air purifier is a good way of reducing the risk of infection from the SARS-CoV-2 virus, but there are ways to maximize effectiveness by understanding how air is circulated around your property.
While the optimal position for each purifier will be location-dependent, here are some general tips:
- Place the purifier near the source of contamination (in the case of SARS-CoV-2, that means near people)
- Avoid placing the purifier near electronics that may run on a similar wavelength, such as TVs, stereo equipment, and microwaves
- Avoid places with high or fluctuating temperatures, such as near windows
- Elevate small portable air purifiers 4-5 feet off the ground
- Keep the purifier away from sources of moisture, such as humidifiers and coffee machines
- Leave a gap of at least 2 feet around the sides and top of the purifier to increase airflow
What if you can’t install an air purifier in a particular location?
While hospital-grade portable air filtration systems are an effective measure to protect your employees, clients, and customers from the risk of contracting COVID-19 on your premises, they cannot be placed everywhere. However even in spaces where air purification isn’t practical, there are solutions to creating a cleaner, safer environment by using natural air circulation patterns.
A simple method of increasing ventilation is to open windows or outdoor air intake vents on HVAC systems and air conditioners. Natural ventilation methods can be enhanced by encouraging airflow. Open multiple windows and doors if possible, and open the highest and lowest windows at the same time to encourage the most movement of air possible. Allow air to circulate throughout the property by opening windows at opposite ends of the room, floor, or building, and keep internal doors open if it is safe to do so. You can also speed up this process by placing a fan pointing out of a window to expel air, and placing another in an opposite corner directed into the room, to draw in clean air from outside.
What businesses can benefit from air filtration for COVID-19?
Hospital-grade portable air purifiers are an excellent solution for many businesses looking to secure their workplaces and keep their employees and clients safe from the coronavirus, including:
- Hospitals and healthcare facilities
- Stores and showrooms
- Office buildings
- Schools and colleges
- Warehouses and storage facilities
In short, any premises where people gather can benefit from air purification in order to reduce the risk of COVID-19 or any other virus or bacteria! While air filtering alone cannot remove all pathogens or render an area completely safe, it is a valuable addition to wider cleaning and sanitation protocols. Staying safe during the pandemic is at the forefront of everybody’s minds, and investing in a portable air purifier can bolster confidence and reassure staff and visitors alike that your business is taking every possible precaution.