BLUEMOMENT

If, when changing fuel filters, you inadvertently tip diesel into a running electric fan heater, the result is a large quantity of grey smoke which sets off the fire alarm. I just thought I would share this useful information.

Interesting set up... fuel filter and running fan heater.

Did it also give a nice boost to the heat output?

No, I'd to open all the hatches to let the smoke clear, so the boat got colder. Clearing up a diesel spill is a horrible job.