which type of refrigerant is the most harmful
Refrigerant In order from the highest to the lowest potential of ozone depletion are: Bromochlorofluorocarbon, CFC then HCFC.
Ammonium nitrate Ammonium nitrate is used in some instant cold packs, as its dissolution in water is highly endothermic. It also was used, in combination with independently explosive "fuels" such as guanidine nitrate,[13][14] as a cheaper (but less stable) alternative to 5-aminotetrazole in the inflators of airbags manufactured by Takata Corporation, which were recalled as unsafe after killing 14 people.[15]