Opening a window can help reduce the risk of indoor COVID transmission. Tanishka R./NPR
We regularly answer frequently asked questions about life in the Corona crisis. If you have a question you'd like us to consider for an upcoming article, email us with the subject line: "Coronavirus Weekly Questions." Here you will find an archive of our frequently asked questions .
In the last two years we've all taken a crash course in understanding how to prevent respiratory infections.
And we've learned that clean air through ventilation (meaning the flow of fresh air through open windows and doors) and filtration (removing particles from the air with a filter) is really important to preventing COVID and other respiratory diseases. Many experts have known this for a long time. Now the public is getting involved.
"Most of the air we breathe in our lives, we breathe indoors," says Richard Corsi , dean of the University of California Davis School of Engineering. And virus particles can stay airborne in unventilated places, increasing your chances of getting sick.
Of course, these particles are not visible. "If people could see COVID in the air, it would make a lot more sense to clean the air in your home, change the air, get fresh air to improve ventilation so you don't have a lot of air circulating where others do People can breathe them in and become infected," says Abraar Karan , an infectious disease physician at Stanford University.
As an individual, what can you do at home, at work, at school, at the gym to make the air cleaner and safer?
We asked three experts.
What is the most basic way to improve ventilation?
"Just having more air in the house helps," says Karan.
Open the windows if you can, says Linsey Marr , a professor of civil and environmental engineering at Virginia Tech. "Especially when you can open them up on opposite sides of the room to allow for cross ventilation: air flows in one and out the other. "
Even if you can't open all the windows or you can't open them all the way, opening the windows a little is still very helpful. "They don't have to be wide open," says Marr.
Opening doors to shops and gyms also helps.
Marr worked with his local gym owner to improve ventilation early in the pandemic. The gym did not have central air conditioning, so filtration could not be relied on. The easiest way was to open the doors. "I calculated the benefit we would have by opening the doors, and it was a lot, so we kept them open all winter," says Marr.
And there have been no known transmissions at the gym, says Marr, who has advised the facility and monitored COVID developments. Even if employees have contracted the virus elsewhere, they don't seem to have transmitted it to work, she says.
How can I improve my home's filtration system?
If you have an HVAC (heating/cooling/forced ventilation) system, there are two main things you can do: run the fan more and upgrade the filter to capture more virus particles. Every HVAC system has replaceable filters that capture airborne allergens and dust, as well as viral particles.
HVAC systems do not typically circulate air 24/7, but only run intermittently when the indoor temperature drops or rises.
To ensure the air is filtered through the HVAC system, "run the fan continuously if you can," says Corsi.
When the windows are open, you can also turn on other fans, like bathroom and kitchen exhaust fans, to "suck in that clean air from outside and get rid of the virus," Mar says. Sure, they can be noisy, but they can create an airflow by pulling air up the ceiling and out of the room.
But when the windows are closed, most home HVAC systems simply circulate the same indoor air, and the standard filters you use may not be effective at trapping tiny virus particles. Therefore, you can also consider replacing these filters with higher quality options such as: B. a filter with a minimum efficiency (MERV) of 13.
"If you put a MERV-13 filter in your HVAC system and let the fan circulate continuously, you're removing a lot of aerosol particles," says Corsi.
Most school ventilation systems can also be upgraded to MERV-13 filters, he says.
However, he warns that not all systems can handle the most efficient filters, so it's a good idea to have yours checked out by an HVAC specialist. You don't want your entire system to fail because it's overworked to pull air through mismatched filters.
HEPA is another type of filter that is even more effective at removing viruses from the air, but most home HVAC units will not work with HEPA filters. However, you can get a portable HEPA air purifier.
Can portable air purifiers help?
"When it says HEPA, it filters over 99% of the air that goes through it," says Marr. "Usually the price depends on the size in relation to the amount of air that goes through them." That means the bigger the device, the more expensive it is.
Finding the right size device to clean the air in a room in an hour or two is important. "There's a big difference between a $50 model that can purge the air out of a closet in a reasonable amount of time, and a much larger model that probably costs $200 or $300 and will purge the air out of one in a reasonable amount of time can clean room. ", he says. March.
But, he says, there are cheaper options: For example, a DIY system with a simple box fan, a portable model that's usually square, has a propeller and often fits in a window, and MERV filters. This "is actually more efficient in many cases" than expensive HEPA units, says Marr.
Known by its developers as the Corsi-Rosenthal box, this DIY filter is easy and cheap to make : create a square shape with four filters forming four sides and the fan facing the ceiling and at the top is attached. A piece of cardboard is glued to the floor, and the home air purifier can be placed anywhere a more expensive air purifier can go.
Karan agreed. "Basically, the Corsi-Rosenthal box is a very cheap way to achieve better ventilation."
Corsi also agreed, and only partly because he was one of the inventors . When he first outlined the idea early in the pandemic, he thought it might be a more cost-effective way to offer air filtration. And that's it: The materials cost between $80 and $100.
"But I also didn't realize how incredibly effective it would be," says Corsi.
According to a study by other researchers, the boxes can be up to 2.5 times more efficient than a $300 HEPA filtration unit.
Whichever portable filtration system you use, be sure to place it carefully. Do not place the device in a corner where it could easily circulate the same air. Keep your air purifier about 12 inches from the wall for the same reason.
For large rooms, two or more units can be a good idea, Corsi says, and you can place them across from each other so all the air in the room is well filtered.
What about those little travel air filters? An advantage ?
You may have seen small HEPA cleaning devices the size of a water bottle that fit in a purse or backpack. But are these little devices really useful?
"You should, and you'll want to direct the airflow," says Marr. "You can clean a small area from a small amount of air."
Just make sure to position the clean airflow as close to your face as possible and place it in front of you on the table or desk.
"By wearing them so that the air is directly in front of you, by working at your desk and blowing air in your face, you can reduce aerosol concentrations when you breathe," says Corsi. "I wouldn't overstate its benefits, but there could be some benefits."
These air purifiers, ranging from $30 to $50, can add another layer of protection when you travel, eat out, or go to work or school.
Should I buy a CO2 monitor to check the quality of ventilation in the different places I am?
"If you're a very cautious person, this can be a good tool for assessing risk in different areas," says Marr.
CO2 monitors measure the amount of carbon dioxide in the air. You can't tell how much COVID is in the air, but if there's a lot of CO2 in a room, it's not well ventilated.
If your CO2 reading is under 1000, you're pretty good. Anything over 1800 is a warning sign that a room is poorly ventilated. At high rates, you're breathing in a lot of "other people's exhaled breath, like drinking water," says Marr, a cute way of saying you're drinking other people's saliva while sharing a drink.
However, these are loose rules based on the size of the room, the number of people present, the wearing of masks and the number of cases circulating in the community.
"I'm not a big fan of using CO2 monitors for very specific analysis," says Corsi. "You are not accurate." But, he says, they're very useful for telling you when the air quality is very good or very bad.
Does the improved ventilation mean I can avoid wearing a mask?
Improving air quality means you get sick less because there are fewer viruses in the air. But it's not 100% effective.
All experts agreed that wearing a mask is one of the most effective ways to further reduce the risk of getting sick or, if you are sick, transmitting the virus.
This means you should continue to wear masks in closed public places when cases are high, as they are now in the United States.
And if you are sick or someone in your household is sick, wearing a mask can prevent the virus from spreading at home too.
"If you have someone who is sick, you should try to have them wear a mask if possible, as it reduces the amount [of the virus] that gets airborne in the first place," says Marr. . And it's a good idea to cover up when you're around to protect yourself.
If a family member gets sick, will proper ventilation keep me from catching COVID?
Yes! It may take a bit of work, but it's possible to stop streaming at home.
As an infectious disease doctor, Karan has treated many patients who have been ill at home by other family members. "That's the only thing we're really struggling with right now," he said.
But "I know there are ways to make the house safer; I did it myself," says Karan.
All of the advice given by the experts here is especially important for preventing cases from spreading around the home: opening windows, blowing air through a fan, using masks as source controls, improving air filtration.
In the hospital room, try to keep the door closed and face a fan blowing through the window so "what you throw into your room doesn't go back into the rest of the house under the door, and so on." ," says Corsi. "It will go a long way in preventing others in the home from getting infected."
Should you be pushing for better air quality in public spaces?
Sometimes you are in places where you cannot control the air quality, e.g. B. at work, at school, in restaurants or companies.
But it doesn't hurt to wonder what improvements these places have made to air quality. For example, if you're worried about your child going back to school in the fall, you can talk to the teacher about opening the windows or using a portable air filter.
"We need to hold companies, and then government, accountable," says Karan, to ensure they improve ventilation and set new indoor air quality standards.
"It's not just about COVID," he says. Cleaning the air can reduce other respiratory viruses such as influenza and RSV, as well as mold and allergens.
It's easy to want to forgo COVID precautions because you think it's the best thing to do. But "people need to know that there is a way to solve this problem," says Karan.
"We will not eliminate COVID. But what we can do is drastically reduce transmission of COVID."
Her verdict: "Airing is the right way."
Melody Schreiber (@m_scribe) is a journalist and editor of What We Didn't Expect: Personal Stories About Premature Birth . versus
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