Funny Homeowner Question Today

[fireandrain 39]

I had a client of mine ask me today why, if a stain soaked rag could ignite in a garage, why won't the new stain on her house exterior (cedar shake) ignite as well? She came home on a super hot day, smelled all of that RS and felt like she had to pose the question... Nice lady, very curious type. I've ben asked this once before and I would love to have a better understanding of the correct answer so I can be better prepared when it's posed to me.

[Apple Roof Cleaning 202]

I had a client of mine ask me today why, if a stain soaked rag could ignite in a garage, why won't the new stain on her house exterior (cedar shake) ignite as well? She came home on a super hot day, smelled all of that RS and felt like she had to pose the question... Nice lady, very curious type. I've ben asked this once before and I would love to have a better understanding of the correct answer so I can be better prepared when it's posed to me.

The soaked rag INSIDE a Garage will get real hot I guess ?

[RPetry 564]

Matt,

Interesting question. Found this site, with testing and pictures, that may help explain the phenomenon.

You may want to relay this info to your customer.

After doing a bit of reading, it seems that oils from grains and plants are more prone to spontaneous combustion than petroleum oils. Linseed oil seems to be one of the worst/best candidates, depending on whether or not you want a fire.

Go to: Wildwood Survival - Fire - Reflectors

[Beth n Rod 1,279]

This is actually a very good question.

Fire requires 3 components to exist [air - heat - fuel]. This is called the fire triangle. Take away one component and fire cannot exist.

A bunched up rag holds air which is one point of the fire triangle

The evaporation process of a voc creates heat.

When contained in a small area such as a pocket of air in a rag, it accelerates the build up of heat until it reaches the ignition point.

On a building or structure, the heat is allowed to dissipate because there is no containment. Without the heat to reach the ignition point, there can be no fire.

:angryfire

Rod!~

[fireandrain 39]

On a building or structure, the heat is allowed to dissipate because there is no containment. Without the heat to reach the ignition point, there can be no fire.

:angryfireRod!~

Okay, lets say its 90 degrees outside when the house is stained. The surface of the cedar shake is really baking in the afternoon sun. Wouldn't this ambient situation contribute to ignition point?

[k2waterwerx 14]

The cedarshake will not get to the ignition temp. However I can tell you tarps smell really really bad when they start to smolder!!!!!!

[KC Deck 14]

Actually fire needs 4 things to take off. It's called the fire tetrahedron.

It needs Air/Fuel/Heat/Chemical Reaction

When you throw a rag soaked with a combustible product into a corner, it begins a chemical reaction. this chemical reaction causes heat, which in turn, warms up the rag, and then rag begins to burn.

Everything has an ignition temperature. Once it reaches the ignition temp it will burn. A deck exposed to the sun does not generate enough heat to cause the stain to reach it's ignition temp. Why, because there is no chemical reaction that is occurring that will cause fire. Im sure, if you break it all down microscopically, there is a chemical reaction, but not enough to cause fire.

[PressurePros 248]

The flash point of a rag or tarp is much lower than that of wood. Spontaneous combustion is a result of a bunch of factors coming together. Those combinations cannot come together on a wood deck or siding because of the rapid rate of heat dissipation and higher combustion point.

[MMI Enterprises 289]

Along same lines as everyone else is saying... The bunched up condition of the rag with all that air in there allowing the reaction internally is like making a heat sinc situation. A container full of stain whether it the can it came in or a solid board has hardly any air internally to work off of to make reaction. A container holding such soaked things as rags or tarps, say like in a box, still has tons of air involved yet plenty of heat holding ability that will bring it to temp.

[Cajun Cleanin 64]

The air to fuel ratio is never going to be optimum on a deck or on siding.

To have fire you have to have the ratio right for ignition it could be to weak or to rich to burn.The rags are ignitied by the decompositon of the solvents in the stain and when they are balled up or stuffed in a can the air to fuel ratio will be more controlled than in the open space on a deck.

[plainpainter 217]

The simple answer is that rags soaked with curing oils and bunched up into a corner of a garage or someplace have a tendency to auto-ignite - and siding doesn't. As to the physics and chemistry of the how's and the why's - tell her that isn't your field.

[Beth n Rod 1,279]

Okay, lets say its 90 degrees outside when the house is stained. The surface of the cedar shake is really baking in the afternoon sun. Wouldn't this ambient situation contribute to ignition point?

No, because it is still quite well below the ignition point which for linseed oil is about 650*.

Rod!~

[Beth n Rod 1,279]

Bump!

It's hot, it's summer...read and be safe.

Beth

[MudDuck 20]

The flash point of a rag or tarp is much lower than that of wood. Spontaneous combustion is a result of a bunch of factors coming together. Those combinations cannot come together on a wood deck or siding because of the rapid rate of heat dissipation and higher combustion point.

Exactly,,,stick a match to a rag and see how fast it starts to burn. Do same thing to a 2X4 on a deck and it won't "catch" as fast. Not even close. It's the heat generation IN the easily ignited rag with fumes trapped in the rag which slows down the evaporation process keeping the concentration level up for longer period of time allowing more heat.

Then POOF!!