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Deterioration is the gradual loss of the Hit Points of certain items due to its storage conditions. This deterioration stacks with other forms of damage to the items in question, and can result in the eventual destruction of the item.


Deterioration is the gradual loss of the Hit Points applied to a susceptible item that is not placed in a safe place. An item is anything that can be hauled by a pawn, and susceptible items include clothing, armor, weapons, and most resources.

Deterioration is akin to an item taking damage from projectiles, explosions, or fire since they all affect the same hit points total and so stack with each other. When an item's hit points reach 0, it is destroyed.

When an item in storage is destroyed by deterioriation a pop-up message will display saying: <ITEM NAME> has deteriorated away in storage. When an item being worn by a pawn is destroyed by deterioriation a pop-up message will display saying: <ITEM NAME> worn by <PAWN NAME> deteriorated away to nothing.

Deterioration and the spoilage of food and corpses due to temperature are completely independent from each other. Both systems run in parallel according to their own mechanics and do not interact unless they cause the destruction of the item in question.

Deterioration rate

The rate of deterioration is controlled by a number of factors. An item's deterioration rate specifies how many hit points are lost per day while left outdoors. Depending on the type of item, it ranges from 0.25/d to 10.0/d. This stat is listed in an item's information tab. If this stat is not listed or listed as '0.00/d', then the item will not deteriorate.

For items with the quality stat, a high-quality item will have a lower deterioration rate than a poor quality item... Read Quality#General for exact numbers.

Other factors can increase this base rate. Being unroofed in addition to being outdoors, rain, and being placed in water all increase the deterioration rate.

Items placed in a shelf do not deteriorate even when otherwise in conditions that would cause deterioration.

Deterioration is also applied to apparel, both clothing and armor, when worn. Equipped weapons and utility items do not deteriorate.

Immunity to deterioration

Several items are immune to deterioration. Note that items crafted from these materials do not neccessarily carry over that immunity however.

Immune items include:

Effects of deterioration

As an item loses hit points, it may also lose its market value. This only applies to items which have not been configured to ignore health when determining price. The XML tag for this is healthAffectsPrice, which defaults to true if not explicitly set in the def or a parent of the def. This is set, for most items, in the base definition from which the item inherits its properties.

Items that do not decrease in market value with HP loss include:[Is this an exhaustive list?]:

If an item loses value with hit points, it loses that value very quickly. An item retains 100% of its value down to 90% HP, then loses 1.67% of its maximum value per 1% HP lost between 90% and 60% HP, then loses 4% if its maximum value per 1% HP lost between 60% and 50% HP, then loses 0.2% of its maximum value per 1% HP lost between 50% and 0% HP. The item will have 50% of its maximum value at 60% HP and only 10% of its maximum value at 50% HP.

The only other effect of HP loss is the effect on mood of a pawn using a damaged item. A human wearing any apparel with hit points 50% or below will get the −3 thought Ratty Apparel. If any worn item is below 25%, the thought will worsen to a −5 Tattered Apparel. Compare them with −6 Naked thought. A pawn does not receive negative thoughts for using deteriorated weapons.

Other than market value, potential mood effects, and hastening the item's destruction, an item's loss of HP does not affect any other stats, including damage output, accuracy, armor value, heat or cold insulation, nutrition, flammability, beauty, comfort, medical potency or quality, etc. In addition, a finished product is not influenced in any way by the deterioration of its ingredients, including in market value or chance of success.


Building a storeroom is one of the first things that a colony should do, as the destruction of required resources and equipment only slows progress and creates more work. But the effects of deterioration can also be used to dispose of junk without having to spend resources or pawn time to do so. Hauling corpses to a stockpile zone in running water, outdoors and unroofed will fairly rapidly get rid of them with no more work.

Additionally understanding what items need to be protected is also important. Many raw resources don't deteriorate and thus can be kept outside without fear, buildings can as well but have a greater risk of being stolen by raiders. As it takes resources and time to build enclose warehouses, having layers of storage areas is helpful.

Version history

  • ? - Deterioration no longer lowers the effectiveness of weapons and armors.