Damaging floors are floors (sectors or groups of sectors) that damage the player while the player stands on them. They form part of the "dangerous Doom environment" described in the game booklets:
- Slime and other radioactive waste: Many of the areas in Doom contain pools of dangerous liquids that will damage you if you walk through them. There are several varieties of waste, each doing increasing damage. If it looks fluid, beware!
Because the damaging effects are determined independently from the flats used on their area, they may be used to stand for different types of hazards and substances, according to the graphics chosen for the floor, such as green slime or lava, and any associated hints. Flaming wall textures may reinforce the idea of a very hot area, radioactive warning signs that "nukage" has leaked, and a level name like Toxin Refinery that hazardous organic substances abound.
Despite the damaging effects, it is often necessary to cross a damaging floor during play. Crossing as quickly as possible minimizes the damage. If the player has armors, then the damage is split between health and armor. Also, the radiation shielding suit protects the player from damaging floors for a limited time.
When a player steps onto a damaging floor, there is a very short delay before the player starts to receive damage. In games using engines that allow jumping (such as Hexen or some source ports), it is possible to avoid damage from the floors by continuously jumping.
Damaging floors do not affect monsters.
The fluid appearance is implemented using animated flats, which include nukage, lava, blood, and the like. Flats are also defined to implement blue water and sludge water, but these are not usually damaging.
In Doom and Heretic, the appearance of the flat does not control whether the floor is damaging. The level designer assigns a special type value to make the floor of a sector damaging when the player is within the typed sector. Thus, there can be (and are) damaging floors that do not have the usual fluid appearance, and sometimes a floor expected to be damaging because of its texture is not damaging. For instance, in E2M2: Containment Area and E2M7: Spawning Vats, there is a rare example of a non-animated damaging floor, using a row of intense blue lights in a trench.
In Hexen, some flats are hard-coded to do damage instead of also needing a sector type (allowing the sector to have another unrelated sector type).
Damaging floor types
The following damaging floor types are found in Doom:
|Sector type||Damage per second||Doom source code comment||Real name||Other effects|
|7||5%||Nukage damage||Nukage pool|
|5||10%||Hellslime damage||Blood pool|
|16||20%||Super hellslime damage||Lava pool||Radiation suit might be nullified.|
|4||20%||Strobe hurt||Flashing slime||Light blinks each 0.5 second, radiation suit nullification again.|
|11||drops steadily until below 11%; Same as Type 16||???||Level end pool||Level ends when health is below 11%. God mode cheat, if player has activated it, is nullified.|
(Damage is halved, rounded down, at skill level 1.)
A specialized damaging floor type (11) is occasionally used in the last room of a level (e.g. E1M8: Phobos Anomaly). Damage is inflicted as with type 16, but when the player's health drops below 11%, the level ends. The player's health cannot drop below 1% while within this type of sector, a fact that has strange consequences when the player is not touching the sector floor. These sectors will not only ignore any radiation shielding suit being worn, but also cancel the invulnerability bestowed by the God mode cheat, although the invulnerability powerup is not affected. This type of damaging floor is featured once again in Final Doom's The Plutonia Experiment and Map 11: Hunted, and also in TNT: Evilution's MAP24: Quarry, and is sometimes referred to as a "Type-11 deathtrap" among players.
Apart from the aforementioned examples from official WADs, the following levels from unofficial WADs end in Type 11 damaging floor sectors:
- MAP32: Mostly Harmful (Hell Revealed) Note: This level only ends in a Type-11 deathtrap on skill level Hurt me plenty or higher. On the lower two skill levels, players must kill a "Romero's head" on a harmless center sector instead of lingering at a damaging center sector until they are about to die.
- MAP14: Metal Meltdown (Hell Revealed II)
- MAP11: Arch-Violence (Plutonia 2)
- MAP28: The Bloodwall (Plutonia 2) Note: Like Map 11: Hunted, this level has a choice of two exit portals: the left portal is the safe exit, while the right portal is the harmful exit.
How damage points are calculated
If no armor is present, the player loses the entire percentage depending on the type of damaging floor. If armor is between 0%-100% (such as when a green armor was the most recent armor-suit picked up), the player loses 2/3 of health and 1/3 of armor, rounded down. If armor is between 100%-200% or if a blue armor or Megasphere was the most recent armor pickup, the player loses half health and half armor, again rounded down. If there is only a few percent armor left, such as with a player who had only picked up armor bonuses for protection, the negative armor percent will be deducted from the health percent.
"Leaky" radiation suits
For the 20% damage types (4 and 16), there is a small chance (6/256 ≈ 2.3%) that the player will be damaged during a given second even if they are wearing a radiation suit. If each of the 60 seconds is considered independently, probability theory gives the cumulative effect as:
|160% or more||0.01%|
Due to the periodicity of Doom's pseudorandom number generator, however, it can be shown that the player instead takes damage as follows:
The latter result presumably should not be accepted at face value, because it assumes that 60 numbers are pulled from the table consecutively, whereas in a real level, other phenomena (such as roaming monsters and blinking lights) would sometimes call the generator as well. Moreover, in stock maps, it is rarely necessary to remain on the same damaging floor for 60 seconds.