Most drivers notice that little dashboard button showing a car with a circular arrow, but many aren’t sure what it actually does. That symbol is your air recirculation setting, and using it at the right time can make your ride far more comfortable—especially during extreme heat, heavy traffic, or dusty conditions.

When recirculation is OFF, your climate system pulls fresh air from outside, filters it, then cools or warms it before it enters the cabin. When you turn recirculation ON, a small door inside the ventilation system closes, and the car begins reusing the air already inside. In other words, it creates a closed loop instead of constantly pulling in new outside air.

The biggest benefit is faster cooling in summer. Since the AC is chilling air that’s already getting cooler, your cabin temperature drops quicker and the system works more efficiently. It’s also helpful when you’re stuck behind smoky exhaust, passing strong odors, or driving through dusty areas. Many allergy sufferers find it useful too, because it reduces how much pollen and irritants enter the vehicle.

However, recirculation isn’t ideal all the time. In cold or rainy weather it can trap moisture and cause windows to fog, so switching back to fresh air (and using defrost) is smarter. On long drives, fresh air can help you stay alert. For best results, keep your cabin air filter clean—most are replaced around 12,000 to 15,000 miles.