While, in general, ventilation is a helpful way to exhaust polluted indoor air and replace it with fresher outdoor air, there are times when it’s a bad idea; notably when outdoor air is dirtier than indoor air.

The American Lung Association published its 2022 Most Polluted Places list, concluding: “You can protect yourself by checking the air quality forecasts in your community and avoiding exercising or working outdoors when unhealthy air is expected” — and, we would add, by not ventilating.