As in a real-life fire situation and not an office training course. If fire extinguishers were sentient beings, they'd probably be acutely aware of a future existence of propping a door open or, in an exciting world, being used to flatten a bank robber or a terrorist. But never putting out an actual fire. They are the Captain Flacks or Fire Extinguisher World.
I have never had to use one, thank goodness, nor do I know anyone who has. I have also never been trained in their use. I only know that they are, most unhelpfully, all coloured red these days, irrespective of contents.