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Can you use a window AC when it’s smokey outside?

What is the smoke?

The smoke might be literal smoke from wildfires. Wildfires are increasingly common given climate change is making summers longer and dryer. 

You wouldn’t want to breathe in smoke for the same reason you wouldn’t want to smoke a cigarette. The smoke can damage the delicate tissue in your lungs.

Another possibility is that the “smoke” is actually smog. Smog is air pollution that obscures your vision and blocks light. Most likely, smog is the product of built-up car exhaust that has not been effectively cleared from your city’s air. 

You also don’t want to inhale smog. Wear mouth protection when going outside is unavoidable.

The final possibility is that what you think is smoke is actually fog. Fog is water vapor that hangs at the city level. It’s basically clouds and perfectly safe. 

Fog forms when the air temperature hovers near but not at the water’s dew point. The dew point is the temperature when water condenses to water and dew forms on grass.

If the “smoke” is fog and not smog or smoke, then you don’t have to worry about air quality. You should be able to check with your local government or weather service to request an air quality rating. This rating will tell you how safe the air is near you. 

Can you use a window AC when it’s smokey outside?

Yes, you can use a window AC when it’s smokey outside. Just make sure you turn off any “fresh air” function if your window AC has one. 

All air conditioners work in basically the same way. They pull heat out of your home and deposit that heat outside. But how exactly they do this makes a difference in whether you should turn them on when it’s smokey outside.

Some air conditioners exchange air with the outside – pushing out heat by blowing indoor air over a heating element. Pushing out hot indoor air results in more outside air entering your home. 

This will either happen directly via an input tube or indirectly as the removal of hot air lowers air pressure in your home and more air enters under doors and through cracks in the window. 

Luckily, window ACs do not work like this. Window ACs have an airtight partition inside the unit. They circulate indoor air over a cooling element and separately circulate outdoor air over a heating element.

The refrigerant passes between the two sections in order to carry heat removed from your home to the heating element. But no air passes between the partitions.