Healthy Home Ventilation

Shelly Miller is a professor of mechanical engineering at the University of Colorado Boulder. Much of her work has focused on how to control the transmission of airborne infectious diseases indoors.

According to Shelly, “Once the virus escapes into the air inside a building, you have two options: bring in fresh air from outside or remove the virus from the air inside the building. The safest indoor space is one that constantly has lots of outside air replacing the stale air inside. In homes, outside air gets in through open windows and doors, in addition to seeping in through various nooks and crannies.”

“Environmental engineers like me quantify how much outside air is getting into a building using a measure called the air exchange rate. This number quantifies the number of times the air inside a building gets replaced with air from outside in an hour. While the exact rate depends on the number of people and size of the room, most experts consider roughly six air changes an hour to be good for a 10-foot-by-10-foot room with three to four people in it.”

“Putting a box fan in a window blowing out can greatly increase air exchange. In buildings that don’t have operable windows, you can change the mechanical ventilation system to increase how much air it is pumping. But in any room, the more people inside, the faster the air should be replaced.”

“Every time you exhale, you release CO2 into the air. Since the coronavirus is most often spread by breathing, coughing or talking, you can use CO2 levels to see if the room is filling up with potentially infectious exhalations. The CO2 level lets you estimate if enough fresh outside air is getting in. Outdoors, CO2 levels are just above 400 parts per million (ppm). A well ventilated room will have around 800 ppm of CO2. Any higher than that and it is a sign the room might need more ventilation. You can buy good CO2 meters for around $100 online; just make sure that they are accurate to within 50 ppm.”

“If you are in a room that can’t get enough outside air for dilution, consider an air cleaner, also commonly called air purifiers. These machines remove particles from the air, usually using a filter made of tightly woven fibers. They can capture particles containing bacteria and viruses and can help reduce disease transmission.”

“Before you go out and buy one, there are few things to keep in mind. The first thing to consider is how effective an air cleaner’s filter is. Your best option is a cleaner that uses a high-efficiency particulate air (HEPA) filter, as these remove more than 99.97 percent of all particle sizes. The second thing to consider is how powerful the cleaner is. The bigger the room–or the more people in it–the more air needs to be cleaned. The last thing to consider is the validity of the claims made by the company producing the air cleaner.”

“If you walk into a building and it feels hot, stuffy, and crowded, chances are that there is not enough ventilation. Turn around and leave. By paying attention to air circulation and filtration, improving them where you can and staying away from places where you can’t, you can add another powerful tool to your anti-coronavirus toolkit.”

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1 thought on “Healthy Home Ventilation”

  1. Use Chlorine Dioxide gas to desinfect the air: that´ll kill all the COVID flying around: no need for an expensive air purifier, and much more effective.

    Then drink 10 ml of CDS (Clorine Dioxide Solution) in one liter of mineral water, divided in 10 parts, one part every hour, during the day, as a prevention against the PLandemia-virus.


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