Assess COVID risk and more with air quality monitors

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Amid the COVID-19 pandemic, many of us have become more aware of the air we breathe. And with the transmission of the virus through the air, we had to worry about plumes of smoke from increasingly severe forest fires. Some weather forecasts now routinely include measurements of outdoor air quality, but most Americans spend about 90% of their time indoors, according to the Environmental Protection Agency. In order to counter airborne health threats at home or in the office, more and more people are now tracking contaminants with portable air quality monitors, and the market for these devices is expected to reach 4.6 billion. dollars in the world by 2027.

Air quality monitors got their start in the 1930s and were once bulky machines that required skilled experts to operate them, but have since become much smaller, cheaper, and more user-friendly. Moderns assess air quality by directing a laser through a small box and determining the amount of its light scattered by particles and other substances in the air. They’re small enough to carry with one hand, and many popular models cost less than $ 200, making them more accessible than ever. Combine that uptime with increasingly smokier summer skies and a pandemic, and “all of a sudden people are really interested in doing what they can to be aware of and monitor indoor air. in some cases – and I think that’s great, ”says Alex Huffman, aerosol chemist at the University of Denver.

What’s in the air?

Indoor air contains pollutants of many sizes, explains atmospheric chemist Christine Wiedinmyer, associate director for science at the Cooperative Institute for Environmental Sciences Research at the University of Colorado at Boulder. Particles 10 microns in diameter and smaller, called PM10, can affect human health and include dust, mold, pollen, diesel exhaust, ozone, and smoke from forest fires. Other particles are created by things like incense, candles and especially cooking. Stovetop frying, for example, has temporary but surprisingly large effects on indoor air quality. Even finer particles 2.5 microns in diameter (about the size of a E. coli bacteria) or smaller, called PM2.5, is the more dangerous category of pollutants: while larger particles (think dust from a dirt road) irritate the eyes, nose and throat, particles PM2.5 can penetrate deep into the lungs and even find its way into the bloodstream, according to the Centers for Disease Control and Prevention. Monitoring this type of pollutant is particularly useful for “sensitive people living in the household (with asthma, chronic obstructive pulmonary disease and other cardiopulmonary problems), as well as for people living far enough away from it all. [outdoor air] monitoring network, ”says Woody Delp, lead author of a 2020 study on air quality monitors. You may also want to track particles indoors “if you live near large outdoor sources, such as roads and large industrial sources,” says Wiedinmyer. “They can create pollution on the outside of your door that can make its way inside.”

In addition to particles, gases called volatile organic compounds (VOCs) are released into the air by cleaning products and furniture glues and varnishes. These substances are found at levels two to five times higher in indoor air than in outdoor air – and “some of these compounds could be carcinogenic, like formaldehyde or benzene,” says Wiedinmyer.

Finally, carbon dioxide molecules are not indoor pollutants, but CO2 the levels can serve as an indicator of the amount of tiny, potentially virus-carrying droplets called aerosols that humans breathe out into a room – and therefore the risk of transmitting COVID indoors. “If we see the CO2 goes up, then that means there is a source of CO2, says Huffman. “If it is about people, we can assume that the aerosols are also increasing.” If the levels drop, it suggests that the room ventilation system is successfully replacing the stale air with cooler, less carbon-containing air.

How to use an air quality monitor

There are dozens of reasonably priced air quality monitors on the market, and most measure particulate matter, VOCs, carbon dioxide, or a combination of the three. Some monitor and display only the current air quality level, while others store the readings over time. Many of these devices come with smartphone apps that download and store data, and present it in easy-to-read screen formats. The Southern California Coast Independent Air Quality Management District, which has extensively tested particle and gas detectors as part of its AQ-SPEC program, offers information on the types of monitors available .

If the priority is to track air pollution, says Wiedinmyer, “number one, I would look for a particle monitor because we know that many health impacts are associated with particulate and particulate levels.” She suggests that a good bonus, but not as crucial, would be sensors that also detect ozone and VOCs. Many monitors display the measured PM2.5 reading and also translate it into an Air Quality Index (AQI) score and color scheme. The AQI “is an index that the EPA has developed to allow people to quickly assess the risks associated with their state of health; they have different thresholds for sensitive people based on pre-existing health conditions, ”says Brett Singer, researcher in the Whole Buildings Systems department at Lawrence Berkeley National Lab. Based on this data, people may decide to take steps to purify their indoor air, which can mean things like turning on the kitchen hood for half an hour (an inexpensive way to purge the air from their homes. home) or invest in an air filtration unit that can operate if diesel trucks frequently idle outside windows or during a forest fire.

For an air quality monitoring device that will help track COVID security, Huffman recommends a specific type of carbon dioxide sensor. “It’s important that people buy what’s called an NDI, or a non-dispersive infrared sensor,” he says. “Most are nowadays, but there are also what are called solid-state sensors, which are not something people should buy in this context. “Since the concentration of carbon dioxide in outdoor air is around 450 parts per million (ppm), Huffman adds:” CO2 above 800 ppm starts to become dangerous ”, as this potentially indicates that the concentration of any COVID aerosol would also be high. With these levels, Huffman recommends opening a window to circulate fresh air. But, he points out, this number is only a proxy; This makes not are directly linked to the COVID risk. For example, when air is circulated through a HEPA filtration system, it can maintain the same level of carbon dioxide even though virus particles are safely removed. And even with air filters, any situation with carbon dioxide above 2,000 ppm could still be risky, Huffman says. This level indicates a high concentration of people exhaling and the filters can only work so fast.

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