Ammonium nitrate is the superior propellant. It is the only one that is non-toxic. You get nitrous oxide (laughing gas) and water vapor in a 2-to-1 ratio. Yes,

Ammonium nitrate is the superior propellant. It is the only one that is non-toxic. You get nitrous oxide (laughing gas) and water vapor in a 2-to-1 ratio. Yes, it can detonate. There are ways to deal with this. Stronger containment is the obvious choice. One might try to ensure detonation to make performance more predictable. Another option is to locate the propellant at a distance from the user, ensuring that shrapnel goes away from the humans. Every other propellant choice is horribly toxic. Air bags perform their intended purpose many times every day. Those people are poisoned. Perhaps they will die of cancer. Replacing the detonating airbags with toxic ones may end up killing many more people than we save.