The lids of pressure cookers are all transparent as far as I know, so you should be able to see if it's empty...
Surely they would not have blown up a clearly empty pressure cooker... right? Right??
You're thinking of slow cookers they tend to have glass lids. Every pressure cooker that I've owned has had a metal lid. I don't remember seeing any glass topped pressure cookers, not saying they don't exist, but I haven't seen any.
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