Most modern pressure cookers are safe if used properly and they have many built in safeguards to prevent accidents. There are locks the cannot be undone until the pressure drops for instance.
Mine is an "old fashioned" "modern" one - not one of the new sleek electric models but a Rival or Mirro available at the hardware store with all the safety features but none of the bells & whistles.
Very simply, put in the ingredients, turn on the heat, when the pressure rises a little knob pops up indicating the lid is locked on and in a few minutes the pressure gauge starts to rattle. Adjust heat, cook recommended time, turn off heat, allow pressure to drop and remove the lid. Instant pot roast, swiss steak or beef stew.
I also use mine for canning jams & jellies. I love it for this because I only have to heat a few cups of water as opposed to gallons of it, takes only a few minutes and since I started pressure canning I have never had a failure of my jars to seal. Highly recommend them. America's Test Kitchen tested them on TV and the results should be online. PS I also think my brother has one that doubles as a slow cooker and he loves it.https://www.youtube.com/watch?v=IiCUKA7dDUs