When I was in 9th grade, I read that mixing potassium permanganate and glycerin would cause spontaneous combustion, so I thought I’d give it a try in our chem lab before class one day. Nothing happened. I was naturally was disappointed so I tossed the mixture in the trash can.
Ten or fifteen minutes later the trash can was on fire! I was fortunate we got it out before the school burned down.
Later on I learned that the KMnO4 must be finely ground. Coarse crystals take a long time to react or may not react at all. I was using coarse crystals.
In your day and my day, trash cans were made of steel which would have limited the damage done by the fire.
Most trash cans today are made of plastic which will only add to the available fuel.
Only a real idiot would start a fire in a plastic trash can.
In the 80’s we used a pinch of potassium permanganate in water as a disinfectant for our greens and vegetables in Haiti. Had no idea until we got back to the US that it had “other” uses.