You have all seen, maybe even used the little foam gaskets that are supposed to block the cold air from coming in through the electrical outlets, as you can see my smoke pencil flowing through the outlet in the first photo. The air sealing experts at CanAm Air Sealing showed me how to make those gaskets even more effective.
First put a small bead of caulking around the backside of the foam gasket. That will seal it to the wall, even if the faceplate doesn't make it tight.
Then take the foam punch-out and plug the child proof plugs and any semi-permanent plugs, like lamps right through the foam to really block the air coming through the contacts themselves.
That's air sealing!