Recycle button on car AC/heater

You can push the recycle button with the AC on, and the fan blows a little harder. Then when the car has cooled down you are supposed to turn it off. Why?

On cool mornings, there is some air coming in even without the vent or fan on. I can cut down this draft by pushing that recycle button (AC and heater are off then). Am I cutting off my oxygen?Some air still feels like it’s coming in, a weak draft. This car has no drafty doors with leaks etc.

We use the recycle button when we’re not smoking in the car. Otherwise, we need the fresh air to come in.


I’ve heard that you want to keep fresh air circulating into your car as much as possible, esp. during heavy traffic.

If you’re sitting in stop-and-go traffic, you risk a build up of carbon monoxide if you leave the recycle button.

You say “cheesy” like that’s a BAD thing.

On colder days if you hit the recycle button, your windows will fog up more. This should be a no brainer in life, but it is amazing how many people just don’t know this.

OTOH, on really cold days, using the recycle button gets the inside of the car warmer faster. This is because you’re heating the (relatively small) volume of air, which is already above ambient, instead of the outside air, which is as cold as a {insert favorite expression here}.

The Cat In The Hat

On several Ford Motor Co. products I’ve owned the relevant settings are “A/C” (outside air) and “A/C Max” (recirculated air). For a long time I thought I was saving energy (and gas) by using A/C instead of A/C Max. It wasn’t until I read the owner’s manual (and who does that?) that I realized I was wrong. It takes more energy to cool the hot outside air than to re-cool the already cooled inside air.

I’ve never noticed the air getting stale or anything, even on long, cross-state kind of trips.

A little off-topic, but I once worked on an airplane that had some instruments that were cooled with liquid nitrogen. Nitrogen isn’t poisonous but if it leaks it could displace all the oxygen in the air (which is a bad thing) and your body has no way of knowing this is happening. As a consequence they had little oxygen meters all over. The first few days I was always checking the meters to be sure I could still breathe! I kept getting short of breath – I was sure we were all going to be asphyxiated! It took quite a while to calm my irrational fears, but I wasn’t used to having to check if there was any oxygen around.

“non sunt multiplicanda entia praeter necessitatem”
– William of Ockham