Take the smallest pilot hole drillbit you have (1/16" or 1mm) and drill 5-8 holes in the bottom of your trash can. This not only allows the air to escape as the bag fills up, but also makes it easier to remove the trash bag later.
I’ve done this with two trash cans now and recommend it to everyone.
The holes could probably be an inch or two above the bottom and still let the air out.