Indoor COVID-19 Mitigation Strategies for Fall 2021

You know it’s coming: you’re going to be guilt-tripped into attending a family shindig during a major holiday during the part of the year (in the Northern Hemisphere) where being outdoors isn’t a comfortable alternative. And maybe some of your family members are refusing to be vaccinated, while others may be immunocompromised. It is a pickle, but there are some things you can do to lower the risk of those gatherings turning into super-spreader events. I don’t know about you, but even though I’m vaccinated, I don’t relish needing to spend an entire week sick, miserable, and in bed!

Risk mitigation is when you take an action or put a control in place that reduces the risk of bad things happening. Mitigations are rarely 100% effective, but they don’t need to be, either. When you combine two or more risk-mitigating actions or controls, you combine the risk-reducing effect they have. Combining mitigations that work in different ways (for example, providing both shade and water to people working outdoors in hot conditions) works better than each action alone does.

1. Everyone Wears a Mask

Pick a mask, any mask. As long as it fits well and is worn properly, a mask can reduce the number of viral particles ejected into the air from your nose and mouth while you are breathing, talking, singing, yelling, coughing, or even sneezing. By reducing the number of viral particles that make it into the air, you also reduce the total number of viral particles in the air.

2. Everyone Wears a (K)N95 Mask

Cloth and surgical masks are great at blocking large droplets. Certified N95 masks and their untested-but-possibly-easier-to-find cousins KN95 masks can stop fine aerosols. They also are much better at keeping air from leaking out via the edges – and they don’t tend to push against your nose the way cloth masks do. Make sure you get the kind that doesn’t have valves – those aren’t as effective because they don’t block viral particles and fine aerosols on the way out. An added benefit is that this type of mask works in both directions – it can help keep viral particles out of your respiratory system (though they won’t keep the virus out of your eyes).

3. Monitor CO2 Levels and Cross-ventilate When Necessary

Researchers at UC Boulder figured out that CO2 concentrations in a space correlate to the risk of covid-19 spread. Properly ventilating indoor spaces to reduce viral spread is a concept that dates back at least to the 1918 pandemic. The tl;dr is that you can use a CO2 monitor to tell you when you need to throw open a window or two and let in some fresh air.

However, a pro-grade CO2 monitor may cost you several hundred dollars, something a lot of people just don’t have. DIY electronics hobbyists have an alternate solution for you, though: DIY CO2 monitors.

There are a variety of plans and tutorials available, all the way from source-all-parts-yourself to programmable gadgets (such as the Raspberry Pi) that just need a CO2 sensor plugged in.

4. Add Ad-hoc Filtration

The EPA recommends increasing ventilation system airflow in both homes and institutional spaces to reduce the spread of covid-19. When modifying an existing ventilation system is cost-prohibitive, or you don’t have any control over it, an in-room filtration solution can help out. Some air filters can be very pricey – but some smart people at an air filter company – working with an environmental engineer at Portland State U – came up with an accessible, inexpensive, high-capacity solution: a 20″ box fan and some 20″ x 20″ MERV-13 rated air filters. The design calls for 5 filters, but if one side of the resulting cube is going to sit flush on a flat surface, you can probably do just 4 filters.

5. Maintain Adequate Relative Humidity

The consistently cold temperatures of winter cause relative humidity to drop. Viral particles (of all kinds) thrive in drier air. The solution? Monitor and maintain an indoor relative humidity of 40-60%. Your respiratory system will be happier. It is also harder for viruses to infect people who have sufficiently moist respiratory passages. Some DIY CO2 sensor modules will also report temperature and relative humidity, so if you’re going to build a DIY CO2 monitor, you may be able to add in humidity reporting!

In Conclusion…

The covid-19 pandemic is far from over. Life tries to go on in spite of that, but we can all take part in reducing covid transmission by adopting mitigation strategies. Don’t think your family will go for it? Try making your attendance contingent on these controls being put into place, and stick to that. Or, host the next one, and make everyone else’s attendance contingent on their compliance. Use FOMO to your advantage, here.

Image: Yoga in a Yellow Suit by Cottonbro