My mother had a canning pressure cooker blow up. She had severe burns and went into shock. Thought she would never touch one again, but the next season she was back at it. She said she tried to help the pressure release along. Just a dumb thing to do. She had worked with pressure canner for years.
I used to use a PS quite regularly, and once I was cooking a pot of soybeans, and had too much in it. And the skins of the soybeans plugged up the release tub that made the weight jiggle (that meant you had the right temp).
Well, as a result the safety blew, not very explosively, but it coated the ceiling with soybean skins
However, running cool water over the pot is a old safe way of making sure all pressure is gone.