# How does "oil on clothing can cause a dryer fire" work if the temperature is too low to ignite? **URL:** \ **Category:** Factual Questions\ **Created:** [April 21, 2024, 4:38pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581 "2024-04-21T16:38:45Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [April 21, 2024, 4:38pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/1 "2024-04-21T16:38:45Z")
You see it on every washer and dryer: “Do not wash or dry clothing in this machine that has ever had any oil on it, it can be a fire hazard” (paraphrased) I was under the impression that a dryer never gets hotter than, say, 170 F inside, even on the hottest settings. Isn’t that far below ignition point for any flammable material? ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [April 21, 2024, 5:01pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/2 "2024-04-21T17:01:16Z")
The risk is not that the washer heats up the clothes to the ignition temperature of the oil. The risk is that the oil that’s left in the clothes continues to oxidise naturally: Oil, and also fat, consists of carbohydrates with more chemical energy than CO2, so there’s the possibility of an exothermic reaction with oxygen from air into CO2. If that heat is trapped in the clothes rather than conducted away, then the risk is that this brings the clothes up to their ignition point. It’s a rather remote risk, but things like that have been known to occur. The risk is greater with oil-soaked clothes than with, say, a bucket of oil because the oil in the clothes has a much larger total surface area that exposes it to oxygen, and the clothes tend to trap the heat. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [April 21, 2024, 5:08pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/3 "2024-04-21T17:08:37Z")
For some oils the risk of ignition is not remote at all, for instance linseed oil and cottonseed oil can easily [ignite spontaneously](https://www.firehouse.com/rescue/article/10528863/the-phenomenon-of-spontaneous-combustion) when they soak rags. No dryer needed. ---
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [April 21, 2024, 5:09pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/4 "2024-04-21T17:09:52Z")
I see, thanks. So this can only happen if the oil has been on the clothing for a long time, and then you wash it? So, if, say, someone spilled a lot of olive oil (or oil-based paint, or gasoline, or whatever) over their shirt, then washed it right away and put it in the dryer, the oil hasn’t had time to oxidize naturally into anything else? ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [April 21, 2024, 5:24pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/5 "2024-04-21T17:24:39Z")
In addition to [some oils](https://en.wikipedia.org/wiki/Drying_oil) being able to self ignite, even if the inside of your dryer drum isn’t above the ignition temperature of the oils, there’s still a heater in there. You might not want something flammable in a dryer evaporating that close to a gas flame or electric heater. I’m not sure if olive oil is a concern, but I’d be worried about oil paints or gasoline. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 21, 2024, 5:31pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/6 "2024-04-21T17:31:40Z")
Note that the whole “oil-soaked rags igniting spontaneously” warning is somewhat overblown. There are _certain_ types of oils (tung, linseed) that are “drying” oils. They release heat when they polymerize. Most common oils (like motor oil) don’t have this property, and don’t present a spontaneous combustion threat. ---
**Author:** ![Snipe70e](https://avatars.discourse-cdn.com/v4/letter/s/51bf81/32.png) [@Snipe70e](https://boards.straightdope.com/u/Snipe70e)\ **Post date:** [April 21, 2024, 10:40pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/7 "2024-04-21T22:40:00Z")
Flash point of many oils is 130 degrees. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [April 22, 2024, 5:03am UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/8 "2024-04-22T05:03:08Z")
No the risk does not increase with a shorter time between oil stain and drying. In fact I suspect it would be inversely related ie the older the stain the more it would already have oxidized and be at less risk of oxidizing. The risk (such as it is) of fire in a dryer through oxidizing oil stains is because if the fabric is already susceptible to exothermic oxidation then the heat of that, combined with the the heat of the dryer, and in a closed location where heat can’t easily escape, might be enough for ignition. Having said all that, I suspect it is @Joey_P who hits the real nail on the head. The real risk may not be one of self-heating but of hydrocarbon stains giving off flammable fumes that may ignite if they circulate in the machinery of the dryer. The hot air blowing through the drum may be only 170F, but the actual heater element has to be hotter than that. And a single spark (such as from an operating relay) can cause ignition of flammable gas. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [April 22, 2024, 5:10am UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/9 "2024-04-22T05:10:54Z")
> [@beowulff](#): > > Most common oils (like motor oil) don’t have this property, and don’t present a spontaneous combustion threat. Motor oil can spontaneously combust if exposed to oxygen under pressure. TBF, not conditions found in your average dryer but more than one welder has had an exciting day not knowing that fact. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 22, 2024, 5:14am UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/10 "2024-04-22T05:14:57Z")
You can also get some impressive pyrotechnics if you pour it on granular pool chlorine (break fluid works better, though). ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [April 22, 2024, 9:29am UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/11 "2024-04-22T09:29:57Z")
The two points above are going to be critical ones. Reaching flash point and available ignition source. The flash point is important. Some hydrocarbons have remarkably low flash points. Mineral spirits is down at 100F, turpentine as bad. Even special high flash point formations only get as high as 140F. Diesel is similarly low, if a little higher. Motor oils are much higher. A tumble dryer might get as hot as 150F. So very much a risk for someone cleaning up after painting. Not so much after changing the car’s oil, but if your fabric has diesel in it, bad. ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [April 22, 2024, 3:09pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/12 "2024-04-22T15:09:07Z")
I’ve known two people to burn down their houses by leaving a rag they used to wipe linseed oil with on a counter overnight. ---
**Author:** ![Nightaudit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nightaudit/32/17181_2.png) [@Nightaudit](https://boards.straightdope.com/u/Nightaudit)\ **Post date:** [April 22, 2024, 6:40pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/13 "2024-04-22T18:40:12Z")
I have had dirty linen bags start smoldering in dirty linen hutch out behind my kitchen a couple of times and several times in the bags themselves in the kitchen…. Dirty food and grease soaked rags do spontaneously catch fire… been there done that got the extinguisher recharge receipts or prove it. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [April 22, 2024, 8:31pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/14 "2024-04-22T20:31:28Z")
> [@Nightaudit](#): > > been there done that got the extinguisher recharge receipts or prove it. What, no Tshirt? ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [April 23, 2024, 6:21pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/15 "2024-04-23T18:21:03Z")
> [@Velocity](#): > > I see, thanks. So this can only happen if the oil has been on the clothing for a long time, and then you wash it? > > So, if, say, someone spilled a lot of olive oil (or oil-based paint, or gasoline, or whatever) over their shirt, then washed it right away and put it in the dryer, the oil hasn’t had time to oxidize naturally into anything else? The oxidation that leads to the build-up of heat is a slow reaction, but it is slow primarily compared to combustion, i.e., fire (which is also an oxidation, a very rapid one). It’s not something that goes on on the timescale of months. So I don’t think a long time since the spill reduces that risk. ---
**Author:** ![Nightaudit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nightaudit/32/17181_2.png) [@Nightaudit](https://boards.straightdope.com/u/Nightaudit)\ **Post date:** [April 23, 2024, 7:20pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/16 "2024-04-23T19:20:45Z")
Just the dirty sweat stained ones from cleaning up the powder gunk from the extinguishers…. ---
**Author:** ![Nightaudit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nightaudit/32/17181_2.png) [@Nightaudit](https://boards.straightdope.com/u/Nightaudit)\ **Post date:** [April 23, 2024, 7:25pm UTC](https://boards.straightdope.com/t/how-does-oil-on-clothing-can-cause-a-dryer-fire-work-if-the-temperature-is-too-low-to-ignite/1000581/17 "2024-04-23T19:25:07Z")
I noticed the dampness of the rags and the amount of food gunk embedded in them affects wether they were able to get hot enough to combust.