Airflow with extractor fan - where does it come from?

[pretzelz]

Hi, funny question perhaps to ask. I've recently installed an extractor fan in the bathroom. It seems to be doing a pretty good job, it clears the humidity after a shower quite quickly.

If I hold a tissue over the vent, the tissue stays on the vent. That way I know it is sucking.

My question is, in a confined space, for example, my bathroom, with lets say no other way for air to go in or out when the door is closed - when the extractor fan is on, and it's sucking air in, where does the replacement air come from? As I assume a vacume is created. And if you say, for example, air can come in under the bathroom door or sides, well if the rest of the house has all doors and windows shut, and no vents, where does the new air come from?

I'm sure there must be an obvious answer.

Thanks. Just interested.

 

[JohnD]

the air comes in through the gap under the bathroom door.

unless you live in a submarine, your home will not be airtight.

funnily enough, yesterday I was in a warship evacuation exercise, where the fake ship had most of the watertight doors closed round our compartment while water gushed in. Luckily there was an open hatch above.