In the air

Ventilation matters with covid

This is a Tale of Two Snots. Think Big Snot and Little Snot, but I will call them droplets and aerosols.

Years ago, I saw an evening outdoor production at the Oregon Shakespearean Festival in Ashland, Ore. Each time the king projected his powerful voice, he spewed out droplets of spit and mucus which were perfectly lit up by the stage lights. Gravity would immediately take over, and the droplets, after their explosive sendoff, would quickly drop downward toward the crowd below and out of the lights. I recall this quite clearly because I was in the second row.

What I didn’t know at the time is that most droplets go down within about six feet from the speaker (although a professional stage actor probably often exceeds the six feet); and 90% of what we spray out are not droplets, but are aerosols, very tiny particles that don’t immediately respond to gravity but instead float and drift with the air currents.

Recently Dean Mark Williams and the UAMS College of Public Health, the Arkansas State Chamber of Commerce, and Arkansas Blue Cross Blue Shield sponsored a conference: Proper Ventilation During Covid (tinyurl.com/uamsvent).

The first two hours are very practical presentations by two experts, Luke Leung and Elliott Gall, on how to make a school, small business, or home safer from covid by improving the quality of indoor air. Since mid-March, which for most of us was the beginning of our personal efforts to avoid infection, we have benefited from outdoor time in spring, summer, and a nice fall.

Outdoor air is safer air. In general, a pollutant indoors is 1,000 times more likely to be inhaled than outdoors. Pollutants are much more quickly diluted outdoors. In the early days of covid, a foreign study did an analysis of approximately 7,500 cases; 7,322 of them were acquired indoors, but only two outdoors. Other summertime factors increase the decay of the virus: more sunshine, higher temperatures, and more humidity.

This is where the aerosols, the Little Snot, become important. Indoors we still get protection from masks and physical distancing, but we put ourselves at increased risk if we ignore the possibility that someone with covid left small aerosolized virus/mucus particles drifting in the air.

Here are some topics to discuss with a heat/air expert.

• Winter air is dryer. A relative humidity indoors of 40% to 60% can be helpful in clearing inhaled virus from lungs. Obviously condensation problems should be avoided.

• If possible, some outside air coming through the heat and air system is very important. In a school or business, proper adjustment of the heat and air system is essential.

• Filtration with a MERV 13 filter or above can be very helpful in eliminating the aerosol particles, but this topic needs to be discussed with a heat/air expert knowledgeable about your system.

• Small portable air cleaner units with HEPA filters may be an alternative. I recently spent some time in a big dental chair in a small room, reassured by a portable filter on the floor beside me.

• In a school or business, pay attention to the direction of the flow of the indoor air. Fans can be very helpful if they are moving fresh clean air into an occupied area. They are not so helpful if they are recirculating air loaded with aerosolized virus/mucus particles from one customer to another.

• Utilizing the heat and air system fan helps particularly if it takes air through a MERV 13 filter. And if air is continuously moving through a filter, and outside air is coming inside in appropriate proportions, it doesn’t take long for a room’s air to be exchanged.

Those are my amateurish attempts to summarize some major points from the webinar. But I strongly recommend going to the UAMS College of Public Health website and spending an hour learning about the aerosolized particles of mucus, the Little Snot, that can deliver floating covid virus to you, your customers, or your students. The hour or two won’t make you an expert, but it will help you formulate the questions to ask.

Recently four Denver Broncos quarterbacks spent time together going over game films. When one of them tested positive for covid, all four were quarantined and missed the next game. My first thought was: What kind of air ventilation was in that room?