Ok, so this time I've been trying to use only one steam vent in a mountain that I've found to make an incinerator, but as it turns out one steam vent can't heat up a room to 200 degrees Celsius quick enuogh to set humans on fire. So what hapened instead was that the enemies started to have heatstrokes. And this is good news because the survivors wont be filled with bulletholles and you wont need to waste your medicine on them. Although, avoid using this one on pirates who pack frag grenades, cause they'll just blow up their friends.
You can check it out in action here
https://www.youtube.com/watch?v=VibjtMVwbKI
Sweet.
Will have to invest in a few heaters aswell :P
I've gone with the same idea, but got there down a different route. I was making vent shafts out of my mountains so that I could have a cooler connected to east h room, so as to always have cool sleeping quarters.
This collection of 20+ coolers all led straight to the outdoors. Instead I put a room on the end of it and made it the entrance to my base. A wall removal meant that colonists could still go outside, and I'd just out the wall back up in the event of an attack. They'd break into the room and immediately be subjected to 230 degrees!
A further improvement I made was to make the previously mentioned ventilation shafts part of the actual maze for them to enter the base. Now they have to walk over 100+ sandbags in 200 degrees. When they all faint, turn off the air con, turn on some backup coolers I have to get the temp to a safe level in the vent, then I send in the rescuers!!
if you worried about temp level (too hot)
make a square of your "heat trap room" a "no roof zone" it'll instantly vent heat to the outside temp.