We all agree we want our clients to feel better when they leave our practice than they did when they arrived. Making sure we stay well is a part of keeping them well too. That’s why all eyes, especially during this time of COVID-19, are on ways we can prevent infections from spreading in our workplaces. A big part of that is paying attention to the quality of the air we breathe when we are at work and sharing indoor spaces with people we don’t live with. For those of us working in close-contact wellness professions, here are some things to consider for achieving the best air quality in the treatment space.

How Viruses Travel

It is important to understand that the virus we are most concerned about now is transmitted through airborne droplets and aerosols that an infected person emits when they sneeze, cough, speak, or breathe. Viruses in aerosol form are about the same size as smoke and vapor particles. Imagine you are in your home, in a bedroom 30 feet away from the kitchen. Suddenly, you perk up—you can smell that someone has made coffee. Your olfactory receptors sense it because the vapor particles have traveled in aerosol form all the way through the air to your room, even under the door and through the vents.

You open the door and are blasted with the scent of that delicious joe, and you are lured to the kitchen. The closer you get, the more your lungs fill with that rich, roasted aroma, and you can almost taste it in your mouth. Now, here’s the rub—viruses travel the same way, only you can’t smell them. The closer you are to them, and the worse the ventilation, the more you will be sharing air and breathing in second-hand aerosols that may be laden with a virus.¹ We also know viruses can travel great distances and linger, which may cause us harm.²

Some experts say the 6-foot rule about social distancing is inadequate, and new evidence shows we should be asking for at least twice that distance. As researchers have demonstrated, an unprotected sneeze can extend 23–26 feet in its combined trajectory and velocity.³

Knowing this, you may feel like throwing up your hands and admitting defeat, resolving to never leave your home again. However, addressing the problem can be as easy as upgrading filters, checking a few gauges, doing some math, flicking a switch, and opening a window or two.

CHECK YOUR HVAC SYSTEM

First, assess your overall indoor environment. Most modern buildings have heating, ventilation, and air conditioning (HVAC) systems, so check to see how well those systems are functioning. HVAC filters are designed to filter pollutants or contaminants out of the air that passes through them. This filtration can help reduce airborne contaminants, including particles containing viruses. The Environmental Protection Agency (EPA) recommends upgrading HVAC filters as appropriate for your specific building and HVAC system, making sure they are of the highest efficiency possible for your system, and are securely fitted and sealed.

HVAC filters are given a minimum efficiency reporting value (MERV) that indicates the size of particulates they can remove; the higher the MERV rating, the smaller the particulates they filter. The EPA recommends using filters with a MERV-13 rating or higher, but to consult your HVAC manual or an HVAC professional before making changes to the filters used in your home or office systems, as demands may differ depending on your space.⁴

The EPA also reminds us that an HVAC filter upgrade is but one element of a larger plan to protect you and your clients, and should be used along with other best practices.

HEPA Filtration to clean the air

Like filters, air cleaners also help reduce particles containing viruses, and may be useful when used along with source control and ventilation. However, it is not a substitute for either method. Source control involves removing or decreasing pollutants such as smoke, chemical vapors, or infectious particles. The use of air cleaners alone cannot ensure adequate air quality, particularly where significant pollutant sources are present and ventilation is insufficient.⁵ Portable air cleaners, also known as air purifiers, may be particularly helpful when additional ventilation with outdoor air is not possible without compromising indoor comfort.

High efficiency particulate air (HEPA) filters were developed during the 1940s to improve gas masks and protect people from radiation particles. They were further innovated in the 1950s and 1960s for use in aerospace and NASA technology, and adapted for use in laboratory and health-care settings. They are rated to filter 99.97 percent of microparticles with a diameter of 0.3 microns or larger, but can actually capture nanoparticles that are only 0.1 microns wide. That means they are capable of trapping the SARS-CoV-2 virus and its variants because those particles are 0.125 microns in diameter.

The reasoning behind this has to do with how the blown microfibers that make up the HEPA filter overlay into a dense, fuzzy, electrostatic web. Also, the more the unit is used, the more charged dust accumulates, and thus, the ability to snatch 0.125 particulates is increased.⁶

Most HEPA air purifiers have a pre-filter that picks up larger particles, dust, and fur, and a carbon layer that aids in absorbing odors. In some models, these layers can be washed and reused; others require regular replacing. HEPA filters themselves cannot be washed, as doing so would ruin the electrostatic charge and texture of the ultra-fine fibers that make them work.

The following are some general considerations when purchasing a HEPA
air purifier.

Efficiency

Don’t focus on special features, but pay attention to the overall efficiency of the unit instead: how effective the filter is, how much energy the machine uses to do its job, how high the clean air delivery rate (CADR) is, and how much replacement filters cost. I recommend Levoit and Blueair products for their high efficiency, efficacy, and overall cost. Coway and Winix are also fine alternatives. (Author’s note: I am not sponsored by any company; this is not a marketing promotion.)

You definitely don’t need to pay extra for combination units that have UV or ionizing functions. HEPA filters with these features will clean the air, but the air needs to be exposed to UV light for a sustained 20–30 full minutes for the process to be effective as a purifying function.⁷ Air moves too quickly through the unit for the UV light to be anything more than a pretty lamp that may increase the ozone levels in your room and damage your interiors over time. Ionizers are not supposed to emit ozone, but many are not built within regulation and can create high levels of ozone that linger. Ozone is dangerous in high levels and can damage the lungs.⁸

If you have a large space, you may need more than one air purifying unit. Think of each HEPA unit as a portable window—they are most effective at ventilating the room if there’s a good cross breeze, so place multiple units in a way that mimics that effect.

Air Changes Per Hour (ACH)

The ACH tells you how many times an air purifier cleans the air in an hour. The higher the ACH, the faster the air is cleaned in the room. For professional health and wellness practices seeking infection control, the best advice is to seek 12 ACH, the equivalent of new hospital requirements for air exchanges.⁹

Clean Air Delivery Rate (CADR)

The CADR represents an air purifier’s efficiency and measures how fast it can filter the volume of air in an enclosed space within an hour. To find out the CADR of the air purifier unit you need, follow these steps.

1. Measure the length, width, and height of the room. Let’s use an average room of 8′ × 10′ with an 8-foot ceiling.

2. Multiply the three measurements together to obtain the overall cubic footage (cf), which is the volume of the space (L × W × H = Volume, or 8′ × 10′ × 8′ = 640 cf).

3. Multiply the volume by the ACH you want. We want 12 ACH, so 640 × 12 = 7,680.

4. Divide that number by 60 (the number of minutes in an hour): 7,680 ÷ 60 = 128 cubic feet per minute (cfm).

If you’re not comfortable with math, there are several CADR calculators you can find online, including the Harvard-CU Boulder Portable Air Cleaner Calculator for Schools found here: tinyurl.com/12yp2b8y.

Look for HEPA air purifying units that have a high cfm. The higher the cfm, the higher the CADR and the more efficient and capable the unit.

Watch Carbon Dioxide Levels and Ventilation

With every breath we take, we consume oxygen and release carbon dioxide (CO2). Indoor spaces prevent ventilation, so that CO2 can build up until it dominates the available air in the space. This can lead to poor cognitive function and drowsiness, and more built-up, stale air means an increased risk of harboring airborne infections. We’re aiming for the freshest air possible, and the best way to measure that is to find out how much CO2 our indoor areas contain. You want your indoor air CO2 levels to be as close as possible to the clean outdoor air CO2 levels. You can monitor this by purchasing a small device that measures the CO2 levels in the air.

The average outdoor CO2 level is around 250–400 parts per million (ppm). The average indoor space with “good” ventilation is about 500–1,000 ppm, so our goal is to get that number down as much as possible to match those outdoor levels.

The best way to do that is by improving ventilation. Opening a window helps, but putting a fan in that window and blowing old air out is even better. Ideally, you would get another fan in another window to draw fresh air in. If you have the benefit of a built-in exhaust system, make sure it vents outside, instead of into your attic or crawl spaces. You want that old air out and fresh air in.

• The standard modern enclosed space is 0.2 ACH.

• One open window will give you about 0.35 ACH.

• Two open windows will get you to 1 ACH.

• One HEPA air purifier will give you 2–5 ACH, depending on the size of your room, what setting you have your unit on, and the capacity of the unit itself, which is measured by cubic feet per minute (cfm).

• This means you probably need two or more small HEPA filters in one room to reach the rate of ACH you need for effective infection prevention.

The Association of Home Appliance Manufacturers (AHAM) is a paid certification service that rates a number of products that filter air. They are not a regulatory body, but they do help with clarifying and testing the claims of the products they review and certify. While finding products rated by them is helpful, it certainly is not required.

Gauge Your Relative Humidity and Temperature

The ideal humidity levels for infection control are between 40 percent and 60 percent, because the immune function of your lungs works best in that range. There is also evidence that suggests we sleep more deeply and restfully in environments with that level of humidity, and a well-rested body is one that fosters a healthy immune system.¹⁰

We also know SARS-CoV-2 can last in the air for more than 24 hours in low humidity and temperatures.¹¹ Keeping our air in the 40–60 percent relative humidity range helps break those viral particles down. Once we increase the humidity up to 60–65 percent, the virus degrades in about 90 minutes.¹² Water vapor can make particles cluster together into droplets, and they tend to stay low and fall to the ground. However, when water evaporates, the particles they once housed dry out and are easily blown about, staying aloft and activated for hours or even days, depending on how well ventilated the space is.¹³

Buying a humidifier for each room you occupy is a wise choice. You don’t need to spend a whole lot to get a decent product. Expect to spend anywhere from $25 to $85, depending on size or quality. The brand I went with is Levoit, but Vicks, Crane, and Honeywell are consistently well-rated too (all sold in North America). Available brands may vary from continent to continent. Wash humidifiers regularly to prevent mold and mildew.

How do you know it’s working? You can easily monitor humidity levels in your rooms by using a hygrometer. These little sensors monitor relative humidity and ambient temperature. They can range from elegant brass fixtures to high-tech monitors. I have two little digital tiles by Govee that I affixed magnets to: one on my fridge and the other on my front door. Each were $10 and are Bluetooth capable, so they communicate to an app on my phone where I can easily see when I might need to refill or adjust the flow of my humidifiers. You can find them at any garden center or at your favorite online retailer.

When it comes to temperature, we know that viruses and bacteria are held dormant in freezing temperatures. When they warm up, they “wake up” and reactivate. SARS-CoV-2 can stay stable and capable of transmission at temperatures below 40°C (104°F) for 3–16 hours and linger in active form for several days on surfaces.¹⁴

For indoor spaces, a microclimate tailored for infection control will keep temperatures between 73–75°F (23° and 25°C), and with a relative humidity level of 60–65 percent.¹⁵

To kill the virus using heat, you would need to expose the air and surfaces to 75°C (160°F) for three full minutes.¹⁶ That could quickly get pretty uncomfortable, so it is best to use the combined approach of keeping the room at a slightly warmer than average temperature, with a higher level of relative humidity.

Don’t Get Scammed

Ultraviolet Light

Most inexpensive germicidal ultraviolet disinfection (also called UVC) units also generate negative ions, which may increase ozone levels in your space. Ozone is damaging to the lungs, so if you decide to use a UVC lamp, make sure you and all ozone- and light-sensitive living things (like plants and animals) are always out of the room and that you always allow a full hour for the ozone to disperse. Do not use ozone generators in occupied spaces. When used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants.¹⁷ Anything left in the shadows while a UVC lamp is running will not be sanitized, so you may need a second or third lamp running concurrently.

That amount of UVC exposure can easily damage fabric and surfaces in your space, and can bleach and degrade most materials over time.

UVC wands are largely useless for the same reason they don’t work in air purifier units: lack of exposure time. UVC needs a minimum of 20–30 minutes to deactivate viruses and kill microbes. You would need to move through the entire room in excruciatingly slow motion for the wand to make any impact. Any exposure to the skin or eyes by UVC can create burns and cause permanent eye damage.¹⁸

Silent Purifiers = Not Effective

Photoelectrochemical oxidation (PECO) filter units that look like modern art or can hang like a masterpiece on a wall may be very pretty and quiet, but they are basically worthless when it comes to filtering microbes, and they don’t do their jobs well at all.¹⁹ Air purifiers with HEPA filters and fans are the gold standard.

Breathe Easy

You care about your clients; otherwise, you wouldn’t have chosen this career. While we may trust each other to do the right thing and reschedule if we think one of us may expose the other to illness, and we believe no decent person intends to spread the virus that causes COVID-19, it spreads anyway. But by masking, keeping our distance, following universal precautions, watching community rates of transmission, and maintaining healthy and well-ventilated indoor environments, we can begin to make our way carefully back to productivity, embracing the good work we are capable of doing. Remember: we cannot eliminate risk, but we can reduce it.

Notes

1. Nicholas R. Jones et al., “Two Metres or One: What is the Evidence for Physical Distancing in COVID-19?” BMJ (2020): 370: m3223, https://doi.org/10.1136/bmj.m3223. 

2. Keun-Sang Kwon et al., “Evidence of Long-Distance Droplet Transmission of SARS-CoV-2 by Direct Air Flow in a Restaurant in Korea,” Journal of Korean Medical Science 35, no. 46 (November 2020), https://doi.org/10.3346/jkms.2020.35.e415.

3. Zeshan Qureshi et al., “What is the Evidence to Support the 2-Metre Social Distancing Rule to Reduce COVID-19 Transmission?” The Centre for Evidence-Based Medicine, June 22, 2020, www.cebm.net/covid-19/what-is-the-evidence-to-support-the-2-metre-social-distancing-rule-to-reduce-covid-19-transmission.

4. Environmental Protection Agency, “Air Cleaners, HVAC Filters, and Coronavirus (COVID-19),” updated January 13, 2021, www.epa.gov/coronavirus/air-cleaners-hvac-filters-and-coronavirus-covid-19; Environmental Protection Agency, “What Kind of Filter Should I Use in My Home HVAC System to Help Protect My Family From COVID-19?” updated January 12, 2021, www.epa.gov/coronavirus/what-kind-filter-should-i-use-my-home-hvac-system-help-protect-my-family-covid-19#:~:text=Related%20Topics%3A-,What%20kind%20of%20filter%20should%20I%20use%20in%20my%20home,trap%20smaller%20particles%2C%20including%20viruses.

5. “Environmental Protection Agency, “Air Cleaners, HVAC Filters, and Coronavirus (COVID-19).”

6.  ASHRAE, “Coronavirus (COVID-19) Response Resources from ASHRAE and others,” accessed January 2021, www.ashrae.org/technical-resources/resources.

 7. Environmental Protection Agency, “Air Cleaners, HVAC Filters, and Coronavirus (COVID-19).”

8. G. Katara et al., “Surface Disinfection by Exposure to Germicidal UV Light,” Indian Journal of Medical Microbiology 26, no. 3 (July–September 2008), www.bioline.org.br/pdf?mb08074.

9. Paddy Robertson, “ASHRAE Recommended Air Changes Per Hour,” Smart Air (August 6, 2020), https://smartairfilters.com/en/blog/ashrae-per-hour-office-residential-school-virus/#viruses; Paul Ninomura and Judene Bartley, “New Ventilation Guidelines for Health-Care Facilities,” ASHRAE Journal (June 2001), www.mintie.com/assets/img/resources/ASHRAE_Article-on-VentilationChanges.pdf.

10. Shane Riddell et al., “The Effect of Temperature on Persistence of SARS-CoV-2 on Common Surfaces,” Virology Journal 17, no. 145 (October 7, 2020), https://doi.org/10.1186/s12985-020-01418-7.

11. K. Chan et al., “The Effects of Temperature and Relative Humidity on the Viability of the SARS Coronavirus,” Advances in Virology (2011), www.ncbi.nlm.nih.gov/pmc/articles/PMC3265313.

12. Akiko Iwasaki, “Another Way to Protect Against COVID Beyond Masking and Social Distancing,” Scientific American (January 19, 2021), www.scientificamerican.com/article/another-way-to-protect-against-covid-beyond-masking-and-social-distancing.

13. Ajit Ahlawat, Alfred Wiedensohler, Sumit Kumar Mishra, “An Overview on the Role of Relative Humidity in Airborne Transmission of SARS-CoV-2 in Indoor Environments,” Aerosol and Air Quality Research, 20 (2020), https://doi.org/10.4209/aaqr.2020.06.0302.

14. Shane Riddell et al., “The Effect of Temperature on Persistence of SARS-CoV-2 on Common Surfaces.”

15. Ajit Ahlawat, Alfred Wiedensohler, Sumit Kumar Mishra, “An Overview on the Role of Relative Humidity in Airborne Transmission of SARS-CoV-2 in Indoor Environments.”

16.  Shane Riddell et al., “The Effect of Temperature on Persistence of SARS-CoV-2 on Common Surfaces.”

17. Environmental Protection Agency, “Air Cleaners, HVAC Filters, and Coronavirus (COVID-19).”

18. G. Katara et al., “Surface Disinfection by Exposure to Germicidal UV Light.”

19. Tim Heffernan, “Molekule Retracts Most of Its Advertising Claims,” New York Times Wirecutter (June 10, 2020), www.nytimes.com/wirecutter/blog/molekule-retracts-most-of-its-advertising-claims.