Clearly, you would be at a disadvantage against someone with heavy firepower; but I think, in those instances, it is designed more to give one an opportunity to escape (without chancing killing the threatening person). Regardless of what they are carrying, being shot with a tear gas/pepper spray round, say in the chest, is going to temporarily stop them. This would make it especially good, for a car-based defense system (as the first video calls it). As a home based system, yes, you are either hoping the assailant isn't packing, or else your plan is to use this to help you get out of the house, to safety, and let the police handle the rest, if necessary. EDIT: I think they say that their design only punctures the CO2 tank, when you are actually pulling the trigger.