Airlock cap on or off

[Steviet]

Hi there, started brewing my first batch of mead last night and I was wondering, does the cap on the airlock need to be on or off? It just came to mind as it is bubbling up nice but I can't see how any air can get out with the cap on.

 

[Kahler]

On.

 

[Steviet]

Haha thanks!

 

[delvorak]

At least on all of mine, there are small holes in the caps to let the air out.

 

[fatbloke]

If its one of those press on red caps, its a friction fit, that allows for the passage of the gas. It's to keep dust, dirt and flys away from the surface of the liquid......