What ‘Proper Ventilation’ Even Means for Your Home

When talking about the ways to reduce the risk of COVID-19 transmission among the people in your own home, public health experts often mention the importance of keeping your home “properly ventilated.” But the instructions end there.

Is ventilating your home as simple as opening a window, or is there more involved? How does ventilation help stop the spread of viruses? And how does this work in the winter? Here’s what to know ahead of any holiday gatherings you may still decide to attend or host.

How does ventilation reduce the risk of COVID spreading?

The idea that fresh air is key to stopping the spread of infectious illness was around long before germ theory emerged and was understood. The early science was murky, but the overall concept is the same: Flush out bad, diseased air with fresh, clean air from outside (or later on, via an HVAC system).

COVID is airborne, meaning it can spread when someone inhales aerosol particles exhaled by an infected person. According to the Environmental Protection Agency (EPA), these particles can travel far more than six feet; in fact, they can move throughout an entire room or indoor space (though the risk of inhaling the particles decreases with distance). Not only that, but the EPA says that the particles can also linger in the air after an infected person has left a room — sometimes remaining airborne for hours.

And while indoor ventilation (whether from an open window or through an HVAC system) is extremely important in helping stop transmission of COVID-19, the EPA stresses that it never eliminates the risk completely. (Which is the reason for indoor mask mandates in public places.)

How to properly ventilate your home

Yes, opening windows is involved, but there’s a lot more you can do to properly ventilate your home. Here are some strategies from the Centres for Disease Control and Prevention (CDC) and EPA:

Bring in outside air

A general caveat here from the EPA: As you’re bringing outside air inside, be sure to keep an eye on your indoor temperature (to make sure it doesn’t get too cold), as well as the air pollution levels in your area.

• Open any windows and screened doors that don’t pose a safety or health risk to children or anyone else in the household (e.g., risk of falling or triggering asthma symptoms).
• Turn on any air conditioner window units that have an outdoor air intake or vent, with the vent open (not all window AC units have this feature).
• If your HVAC system has an outside air intake, open it (although the EPA says that it’s not a common feature, and to consult your manual before doing anything).

Move stale indoor air outside

• Use fans to move your indoor air outdoors, either by using a window exhaust fan, or a table fan. If you’re using a table fan, make sure that it’s placed as close as possible to an open window or door, blowing outside — and also that it’s placed there safely and securely. Don’t leave fans unattended with young children, CDC advises.
• The exhaust fan over the stove and your bathroom fan can also help push indoor air outdoors. If you have guests from outside your household, the CDC recommends keeping the fans running for an hour after they’ve left.

Encourage indoor airflow

Even if you aren’t able to open your windows or doors, using fans around your home can help improve the airflow:

• Turn on the ceiling fans in your home (as long as they’ve been dusted and cleaned).
• Make sure any table or box fans are pointed away from people (so contaminated air doesn’t flow directly at them).

Filter the indoor air

If your house has a central HVAC system (meaning there air ducts that go throughout the home) that you’re able to access, here’s how to use it to filter your indoor air:

• Use pleated filters, as they’re more efficient than regular filters — but have a professional install them.
• Check to make sure the filter you’re using actually fits the unit.
• Change your filter every three months (or according to the manufacturer’s directions).
• If your HVAC fan operation can be controlled by a thermostat, set the fan to the “on” position instead of “auto” when you have visitors (or want increased airflow in the house) to keep the fan running continuously — even if your heating or AC isn’t on.

If your home doesn’t have a central HVAC system (or you want to add another layer of filtration) you may want to consider getting a portable high-efficiency particulate air (HEPA) cleaner. According to the CDC, “they are the most efficient filters on the market for trapping particles that people exhale when breathing, talking, singing, coughing, and sneezing.”

Additional tools and information on ventilating your home

If you’d like more information, or to get a little more scientific about everything, the CDC provides a free Interactive Ventilation Tool that prompts you to enter some data about your home, and then lets you know how well-ventilated it is, and how to improve the situation. For even more specific information, check out the expanded version of the model from the National Institute of Standards and Technology.