Deterioration

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. 
== Summary ==
Deterioration is the gradual loss of the Hit Points applied to a susceptible item that is not placed in a safe place. Deterioration is akin to an item taking damage from projectiles, explosions, or fire - they all lower the same HP total, so they all stack with each other.
Susceptible items include clothing, armor, weapons, and most resources. When an item's hit points reach 0, it is destroyed. Deterioration does not impact the protective stats of armor, weapon function or quality of item. See #Effects of deterioration for details.
* 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 ===
An item's deterioration rate specifies how many hit points are lost per day, while left either unroofed or outdoors. For example, packaged survival meals deteriorate at 0.25 HP/day, while rice deteriorates at 6 HP / day. This stat is listed in an item's information tab. For items with the quality stat, a high-quality item will have a lower deterioration rate than a poor quality item (see Quality#General for details). If this stat is not listed or listed as '0.00/d', then the item will not deteriorate.
Deterioration rate is then multiplied by being in rain (x5) or being placed in watery terrain (x3 on marsh or any water tile). Items placed indoors do not deteriorate. Items placed in a shelf do not deteriorate even when otherwise in conditions that would cause deterioration. Equipped apparel - both clothing and armor - deteriorate 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:
* Metals 
* Stone
* Persona core
* Artifacts
* Minified furniture and buildings
=== 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:
* Wood (and technically metals and jade have the healthAffectsPrice tag too, but they don't use HP so it's irrelevant)
* Textiles
* Raw plant matter such as hops, psychoid leaves and smokeleaf leaves; and also including wort
* Raw animal products such as milk, insect jelly, eggs
* Meals including pemmican and kibble
* Drugs 
* Medicine (including neutroamine)
* Components and Advanced components
* Chemfuel
* Basic subcores, standard subcores, and high subcores
* Signal chips, powerfocus chips, and nano structuring chips
* Genepacks and xenogerms
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% of 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 thought Ratty Apparel. If any worn item is below 25%, the thought will worsen to a Tattered Apparel. Compare them with 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.
== Analysis ==
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.
* Beta 19/1.0 - Item deterioration rate now takes into account several factors, including being outdoors, being unroofed, and being in water
Category:Game mechanics