JUST BREWED MY 3rd BREW AND AFTER 24HRS THERE WAS NO AIR LOCK ACTION,AFTER INSPECTION I FOUND I HAD A LEAK AROUND THE AIR LOCK GROMMET,I SEALED IT . NOW I AM WONDERING IF THIS IS GOING TO AFFECT THE BATCH.
Don't worry about it. Like Kephren says, fermentation will produce pressure inside the bucket, that will keep bugs from "dropping in." Also, if your yeast is producing krausen or foam and crud on the surface of the beer, it is healthy, happy and crowding out most bacteria that might want to infect your beer.