I have access to a lot of acetone at work. We print using PLA filament and I found if a nozzle is really clogged you can get most of the gunk off by soaking it in acetone. I have a jar with maybe 30 or more old nozzles left by a coworker who would just order new ones instead of cleaning them. Some of them were blocked solid by burnt on PLA.
Whenever I need a clean nozzle I go to a room with good ventilation and take one out of the jar and run a needle through it to get rid of the last of the filament crud. Anything left behind is minimal and passes through as soon as the next print is started.
No issues so far. Any acetone has long evaporated by the time the nozzle is exposed to heat.
Jake