Why is there air to breathe inside a car or a shed?

Air is inside because it slips in. Tiny cracks let it come through. Doors bring in more air too. You can breathe it in there.

A car or shed is not closed like a perfect jar. It has tiny cracks, holes, or vents. When the door opens, even more air comes in. So the space fills with air you can breathe. It is like your bedroom: even with the door shut, air can still sneak in around the edges, so it does not run out right away.

There is air inside a car or shed because they are not completely airtight. Air is a mix of gases, including oxygen, which your body needs. It gets in through vents, tiny gaps around doors and windows, and any time a door opens. If people stay inside with no fresh air for a long time, the air can become stuffy. Fun fact: many cars have hidden vents that let air escape when you shut the doors, so your ears do not feel as much of a push.