The raws (namely fire.lua) give a lot of information, but not all.
First for completeness, let's start with the easy two (base damage only):
- The "Fire Sticker" deals 16.67 damage every 10 ticks, and lasts for 30 seconds, dealing 3000 damage in total.
- The "direct splash" deals 3 damage every 2 ticks, in an area about as big as a biter spawner.
- While "Fire Flame" is defined in the raws as doing 13/60 damage per tick, it actually deals 10x that damage every 10 ticks. In the raws I can't see where this "10" is defined, maybe I'm dumb, but frame by frame analysis makes it very conclusive.
- To know how much damage a fire patch will do when it "ticks", you can take the damage/s numbers from the Flamethrower turret tooltip under "Creates: 1x Fire", first multiply it by 6, because it can actually be intensified up to 6x, then divide by 6 because it "ticks" 6 times a second, so really you didn't need to do anything to it: when fully intensified the fire patch will inflict that much damage, not per second, but 6 times per second, you can just compare flat resists with that number. It will deal 6x that damage per second. Clear as mud? I hope so.
- When a fireball stream hits the ground, the "fire patch" grows bigger, with a lot of individual hit circles for the individual fire flames visualized as pink in the fire debug setting, if something's collision box touches one of those circles, it will take damage from that fire patch. It doesn't matter "how in" an object is or how many flame circles it overlaps, the damage is not increased. For example all three cars take the exact same damage from this fire patch despite one being entirely inside it and another barely touching it:
- Screenshot From 2025-01-29 15-25-42.png (893.73 KiB) Viewed 309 times
- In "show fire info" debug view, there's a black circle encompassing a fire patch, if a fireball lands inside the black circle, it intensifies that fire patch, if it lands outside a black circle, it creates a new fire patch. This means there's a maximum density at which fire patches can be created. The pink "burn circles" of the individual flames can extend quite far outside the black circles, so for a well intensified firestorm it's actually possible for a collision rectangle to be contacting like 6 or more individual fire patches.
- Screenshot From 2025-01-29 15-49-37.png (1.1 MiB) Viewed 309 times
- Because fire patches have a cooldown between intensifications, having multiple flamethrower turrets shooting at the same location does not intensify the fire patches any faster. While this is "obvious" from fire.lua, I confirmed it using frame by frame analysis and the debug fire overlay and video comparison and 5 turrets and 1 turret both resulted in an identical rate of intensification.
Refined flammables applies the damage bonus twice to Flamethrower turrets. I always get people who try to deny this reality, but honestly it's clear as mud in the tooltips, if you look closely enough, and squint. Refined flammables applies a bonus to Flamethrower turret, and Flamethrower ammo, but Flamethrower turret is defined as having "Ammo category: Flamethrower ammo", hence it receives the bonus both for being a flamethrower turret, and for "using" flamethrower ammo (this same method is used so Tesla turrets get the bonus for tesla ammo despite the electric damage upgrade not applying directly to Tesla turrets). I think once upon a time this relationship could only be seen in the raws, but now ammo categories are listed in the Factoropedia. Also the flamethrower damage tooltip only makes sense if the bonus is applied twice multiplicativity.
Anyway, this means that Flamethrower turret damage escalates rapidly with Refined flammables levels.
Most things in the game don't have flat fire resistance, and most those which do don't have enough to matter much. Medium+ worms, spawners and egg rafts mostly have 3 flat fire resistance. That actually negates the "direct splash" at lvl0 flammables, but it doesn't do much to the 13 base damage of the fire patches, as long as you actually intensify them to max, a single splash fire patch is only doing 2.2 damage, though the personal flamethrower gets the first intensification for free, so actually starts at 4.4 damage, this is largely negated by the 3 flat fire resist, so when burning worms and spawners it's always important to intensify fire patches, and also spread them out enough to make independent fire patches. If you're burning spawners with Flamethrower turrets, the upgrades actually help quite a bit more, since the Flamethrower turrets are usually only going to create a single fire patch, that makes their direct splash a lot more important, but still, Flamethrower turrets will eventually get the job done even at lvl0 flammables.
More importantly, are Tanks and Trains, both of which have 15 flat fire resist. That means with no flammables upgrades, fire patches with their measly 13 damage do nothing to tanks and trains, they can literally sit in a fully intensified fire patch for multiple minutes before being destroyed.
However even the first refined flammables level brings the damage up to 18.72, which is now above the flat 15 fire resist, and even though the flat fire resist is taking a big chunk out of that damage, it still massively increases the damage taken. The next level, brings it up 25.48 damage, now Tanks and Trains really start to feel it when they sit in a fire. If you go to flammables 6 (the last pre-infinite level), now it's 78.88 damage, the 15 fire resist is doing basically nothing, tanks and trains burn as if they're biters. For example if a Locomotive sat in a firestorm getting hit by 5 fire patches, it would take over 1000 damage per second, if it's moving it's okay, but if has to stop because it bumps into a biter, it's dead.
Construction bots don't have any flat fire resist, instead they have 85% percentage resist, even with their puny 100 health, that's still enough to give them high effective health to fire. For construction bots, there aren't really any thresholds where the fire starts hurting, it always hurts them even at lvl0, and it just hurts more with each level. Generally I consider advanced flammables 2 to be a fairly safe level for construction bots, level 3 is getting dicey, and at 4+ the bots are going to die in droves.
Funny thing is though, you only need lvl0 refined flammables for flamethrowers to be highly effective against spawners and worms, and can easily achieve firestorm intensities sufficient to incinerate a big biter in half a second. You only need lvl1 for a single splash to be a touch of death for a Behemoth Biter. More levels in refined flammables are mostly just improving the ability of your flamethrower turrets to destroy your own bots and trains, with some argument for taking out Behemoth biters faster.
The TL;DR
