Incendiary
Incendiary rounds are available for the Heavy Cannon, Auto Cannon, and Rocket Launcher. These rounds do some impact damage but also set the target and the surrounding area (in the case of the rocket, a LOT of the surrounding area) on fire, with the following results:
Smoke
- A burning fire can also be used as an impromptu smoke screen.
Light
- Especially useful during Night Missions, fires not only damage aliens and obstacles hiding in dark corners of the map, but also illuminate them for several turns.
Damage
- Brush and wood on fire will eventually be consumed, leaving a flat scorched earth tile.
- If a Zombie is killed by the explosive impact of any form of Incendiary munitions, the Chryssalid larva will be burnt up instead of hatching.
- UFO interiors and dropped items are fireproof, even if their owners aren't. Silverblade recommends combining this fact with the diagonal wall bug and an incendiary rocket to roast them in the shell.
- Damage caused by fire does not alter Morale level.
- All forms of manufactured X-COM armor will completely block the effects of fire. Soldiers not wearing armor take damage directly to Health, bypassing armor.
- Tanks/Hovertanks have a susceptibility to incendiary of 40% which means they will take damage from fire.
- Initial "impact" damage from incendiary ammunition is either for no points (unit does not catch fire), or between 5-10 points (unit catches fire). Since the distribution is normal (flatline), the probability of remaining unharmed is 1/7 = 14%, while there is a 6/7 = 86% chance a unit will take some damage.
- Units standing in a blaze will receive between 1-12 damage points, most likely determined by flammability rating of tile.
- Aliens or unarmored soldiers standing in flames have a 33% chance of catching fire (observation from 6000+ trials), and once lit will remain that way for 1-5 rounds. Units on fire take between 5-10 damage points until the flames burn out. Smoke will not snuff out a unit fire.
- Fire will continue to do damage until the unit falls unconscious or dies.
- Ultimately, in comparison with other ammo types, incendiary is a weak form of damage and not the fastest way to take out an alien.
Spreading
Fires spread. A tile surrounded by flaming tiles will likely catch on fire next turn. This can make for a fairly rapid spread, up to one tile radius per turn, in ideal conditions (such as wheat fields and haylofts). However, the fires go out eventually and the nearby tiles have a chance to not catch on fire, limiting indefinite spread.
A soldier can walk through flaming tiles but try not to be left standing on or next to one by the end of the turn as that's when the fire spreading code runs. Incendiaries also have the effect of restricting alien movement as they'll tend to avoid the fire.
Regular explosives and explosive ammunition also have a chance of starting fires - particularly in the mountain maps. Copious use of explosives on thick cover help prevent the enemy from using cover or shooting back.
Explosives will not put out a raging blaze. However, destruction of flammables on a tile via explosions may lower the chances that tile will catch fire and may allow a team to direct or even corral the flames.
Quirks
The XCOM game makes a brave attempt to model fire. However there are some quirks:
- If a unit (alien or friendly) is on fire or standing in flames, an incendiary explosion anywhere else on the map will damage it, even if you just shoot an IC round at a random patch of ground.
- Friendly units standing in smoke will take STUN damage every time an incendiary round explodes. However, alien units will be unaffected (admittedly, this was only tested against Sectoids).
- There is an upper limit to how many squares can be on fire. Once you have a good sized blaze going, for example a forest fire, further incendiary rounds will seem to fizzle as no more fire can be created. Impact damage will still be dealt.
- The damage value listed in the Ufopaedia does not determine how powerful the incendiary round deals damage. It only determines how wide an area will be blanketed with flames. Impact damage and damage over time have set damage values.
- Smoke and flames do not mix. Only one type may exist on a tile in a particular instant. To quickly smother a blaze simply drop a primed Smoke Grenade in the center. This is a fairly useful trick for unarmored soldiers who want to safely cross a blaze without waiting for it to burn out by itself.
Thanks to Silverblade-T-E and NKF on StrategyCore forums. --JellyfishGreen 13:04, 4 Jul 2005 (BST)