Here’s a way you can be prepared to effectively break glass without paying up for a more expensive glass-breaking tool. I recently learned that ceramic shards from a spark plug can be very useful in effectively and quietly breaking glass. Take some old spark plugs, place them between a heavy cloth and tap them with a hammer. The remaining shards can be tossed at a window and it will shatter in a much quieter fashion than if the glass was hit with an ASP. For quick access, keep the shards in a cloth bag you can stow away or keep in a go bag.
This works very well with windows at elevated heights that are otherwise hard to reach. Be cautious, though, as these shards are very sharp. If anyone has heard of this and found different results please reply.