If you go to sleep and are cold, so to keep warm you pull the covers over your head, will you suffocate?— Jeff
Let's look at it this way. If you were to seal yourself in a big garbage bag that had no holes in it, you would definitely suffocate. But if you were to perforate the garbage bag with thousands of pinholes, you would not. Oxygen would diffuse into the bag and carbon dioxide would diffuse out through the holes. If your blanket is like a piece of plastic and does not allow any air to pass through, then you should not sleep under it. But if it lets air through, you do not have to worry about suffocation.
That being said, infants in cribs should not have blankets because of the risk of suffocation.