The Centers for Disease Control posted updated Covid-19 transmission information on its website last Friday and removed it on Monday, claiming the posting was done in error with draft copy. The crucial information in the update concerned aerosols and small airborne particles carrying enough of the virus to infect people beyond the six-foot radius often cited as a safety margin, especially within poorly-ventilated spaces. This mirrored guidance that the World Health Organization addressed last July.
Aerosolized transmission can have a significant reopening impact for schools, gyms and other public and commercial facilities – but it also impacts living spaces, including homes shared by multiple family members, dormitories, military barracks, assisted living facilities and nursing homes. “The CDC has been saying for months that large droplets are responsible for most infections,” notes Jose L. Jimenez, an aerosols specialist and professor in the University of Colorado at Boulder’s chemistry and biochemistry department.
“These are projectiles of saliva or respiratory fluid that travel ballistically between two people,” he explains. “Aerosols are smaller bits of the same materials, saliva or respiratory fluid. Because they are smaller, they stay floating in the air from tens of seconds to hours. They infect by being inhaled, and depositing into the nose, lungs, or other parts of the respiratory tract.”
Aerosols Increase Transmission Risk
Why is this such a bigger challenge than the current guidance, based upon the virus being carried in droplets? “Large droplets can only infect in close proximity,” Jimenez says. “Aerosols infect much more easily in close proximity, because they are much more concentrated there, just like the smoke being breathed out by a smoker (smoke is an aerosol). However they can build up in a shared room air if there is low ventilation, long time etc., and lead to infection that way.”
Jimenez believes the current guidance is inaccurate: “If large droplets dominated infection, we would almost only see infection in close proximity. If aerosols dominated infection, we would see a lot of infection in close proximity (due to their being much more concentrated there, like smoke), but also infection in shared room air when the conditions were favorable (like those that lead to a smoky room). Also, if large droplets dominated infection, we would see very similar infection rates outdoors vs. indoors, because large droplets that have enough inertia to reach another person are not easily affected by winds outside.”
Impacts and Prevention for Residential Spaces
“If large droplets dominate, then one is safe indoors with distance and washing our hands. If aerosols dominate, all of that is false. It is still easy to get infected in close proximity. But one can also be infected indoors, as more of the elements that favor transmission are present (long duration, low ventilation, crowding, no masks, talking or shouting/singing),” the professor explains.
What should you do to keep yourself and your loved ones safe indoors? “If people there are staying in one ‘pod,’ then not many additional precautions are needed. Otherwise, and especially if an infected person is present, isolating that person and ventilation is a good idea. Keep windows open as much as possible,” Jimenez advises.
The challenge is greater in multi-family buildings and congregate living spaces (like dorms and barracks, for example). He recommends, “Avoid indoor activities with others not in the same pod. Do things outdoors whenever possible. If indoors, reduce the number of people, ventilate, (open windows and doors, or through HVAC systems if they exchange indoor and outdoor air), keep the fan on all the time through the thermostat, so that the air is constantly filtered, make sure everyone is masked and the masks fit snuggly (no gaps), reduce duration. If needed, use portable HEPA filters to remove viruses from the air.”
Building and Remodeling Advice
If you’re shopping for a new home, or planning to remodel or upgrade your existing residence, Jimenez recommends, “Install HVAC equipment that can handle higher quality filters that retain more particles, and include some intake of outdoor air, so that it is not indoor air just being constantly recirculated.”
The same advice applies to professionals building shared living structures, he says, but with an additional caveat: “Make sure that there is no air exchange between units, but that all exchange is with the outdoors.”
Indoor Air Quality Awareness Increases
Indoor air quality has always been an important consideration for those with respiratory issues and compromised immune systems, but it has taken on much more awareness among the larger population because of the pandemic. “Air purification systems are considered by many to be a critical supplementary approach to reducing transmission rates,” shares Paul Scialla, founder and CEO of Delos, a wellness real estate and technology company, and founder of the International WELL Building Institute, which has created a new wellness-related certification program for buildings and professionals.
The company’s DARWIN Home Wellness Intelligence Network integrates with Crestron’s smart home system to monitor and manage indoor air and water quality. Standard residential HVAC systems are often inadequate to address IAQ issues. “Traditional filters do not efficiently filter air particles as small as SARS-CoV-2 (.06 to .14 microns) in occupied spaces, where it matters most,” Scialla points out. (This is why experts recommend HEPA filtration, but many standard systems don’t perform efficiently with it.)
“Parameters like fine dust (particulate matter (PM) 2.5 micron), Carbon Dioxide (CO2), and Humidity affect the transmission rate and survival of the virus,” notes Ellie Amirnasr, CEO of Qlair, another technology-based solution for IAQ management designed for multi-unit facilities. This system adds another proven virus killer, UV light, to deactivate the particles captured by HEPA filtration.
Big Three IAQ Factors
Filtration is the first factor Michael Don Ham cites as one of the three tools in removing the virus that causes Covid-19 from living spaces. “Most people are familiar with HEPA filtration that removes 99.97% down to 0.3 microns,” the COO of Pure365, another wellness technology provider, observes. “The latest innovation in filtration is to remove ultra-fine particles at a greater than 99.99% efficiency and these systems are going into schools, office buildings, fitness centers, senior housing facilities, as well as residential homes and buildings. The latest research shows that airborne viruses can spread on dust, so reducing the amount of particulate in the air effectively reduces exposure to microorganisms,” he shares.
Ventilation is the second factor Ham cites. This can be done through the original venting method – opening doors and windows – and through technology-based systems to activate fresh exterior air access when needed and heat or cool it before it enters the space.
Humidity control is the third IAQ factor. “It is important to keep relative humidity in a space between 40% to 60%. When the air becomes dry our critical defense mechanisms, which prevent pathogens from reaching deep inside our lungs and bloodstream, are compromised.” Smart home systems let residents set their desired humidity level, just as they do temperature levels, to keep the space at a healthy, comfortable setting. This can also help avoid mold issues in damp basements and bathrooms.
“Many homeowners already have whole house filtration, humidifiers, dehumidifiers and fresh air intake fans, but may not understand how to get them to work to optimize the indoor air quality in the home,” Ham observes. This is why interest in wellness technology firms that automate IAQ management like Pure365, Delos, QIair and others is surging in this health crisis.
If you don’t have thousands to spend on full systems like these, Ham suggests, “You can start with either of the three main components that ensure high indoor air quality – filtration, ventilation, humidity control – and then add components over time. For those in wildfire zones, filtration would be a priority. Others who live in low and high humidity zones may need to add a humidity control component to improve health.”