Most children of school age who wet the bed at night have what doctors term primary enuresis.. They have never had nighttime control of their bladder. Family history plays a role, too, in incontinence in children. If you wet the bed as a child, don't be surprised when your child does, too.
One thing to notice is that if you put a gallon of air on a scale, (in a wieghtless container, of course) you would measure zero, exactly. That's because the buoyancy caused by the surrounding air exactly counteracts the weight of the air in the container. If you pressurized the air in your gallon container to, say ten times the outside pressure (or 147.0 psi absolute, or 132.3 psi gauge) it would now weigh nine times 0.01, or 0.09 lb.
1 cubic foot of air weighs 0.0807 lbs at standard preasure and temperature. there is approx 80 cubic feet of air in a normal rental tank at 2400 psi. so the air in the tank weighs approximatly 6.4 lbs. If you enter at 2400 and exit at 500 then you will be about 5.1 lbs lighter than when you went in.