26 days ago - SylenThunder - Direct link
Originally posted by Metalhead123: ...
Also fairly recently i think they added screamers triggering off Mining the metal ores (Iron/Lead) so if you are mining in the bunker then you could get some unsavoury visitors. I think you are safe if you are mining stone, coal, or Nitrate though.
This isn't recent. It's been a thing as long as the heatmap has existed. The only recent change was around a16 when torches and candles were coded to generate heat.

Generally speaking, their detection range is about 30-35 meters. So if you are more than 35 meters from the surface, screamers will not detect you when they come hunting. They will still come because the heatmap is infinitely vertical, and when the heatmap hits 100 a screamer scout is spawned to investigate. I usually leave some kind of defensive measure above ground to deal with them.

If you're going to have a lot of things running, it's good to spread them out a bit. Heat is generated inside the chunk area. So if you have two forges that are in separate chunks, their heat will not be combined. It would be like only having one. A chunk is 16x16 blocks.
25 days ago - Shurenai - Direct link
Also just to clear something up so we can all move towards using the right term, The proper term is "Activity Map"; Not "Heat Map".

And Heat Map before was not in relation to Temperature, But to the frequency of events, like a keyboard heatmap that shows which keys you hit most often vs those you hit least often.

The Activity Map is a sum of events that make sound/light/smells/etc that the zombies can pick up on, not a rise in temperature in the area.