Some fires can provide their own fuel through the decomposition of other materials.
For example, a lithium battery fire produces oxygen as it burns, so it is self fuelling and smothering it with water is not an effective way to put it out. Lithium is also highly reactive with water, so the water itself may act as an accelerant and make the reaction more violent.
In addition, most lithium fires involve electrical systems, and (although water is not a great conductor), it is possible to be shocked or electrocuted if the voltage is high enough or if there are impurities in the water and it is able to conduct through it to the person fighting the fire.
Normally, putting water on a fire either smothers it from oxygen, or cools it down enough to stop the fire.
With grease fires, that doesn’t happen.
Water is denser than grease, so it sinks below the grease. As it takes in heat, it boils. When it boils, you have a pocket of gas under the liquid grease. It throws flaming grease in all directions as it expands up and pushes out. This causes a grease fire to spread.
You pour in water. But the water is heavier than the oil, so it flows down into the oil. Here, it heats up, rapidly, and turns to steam which bubbles up through the oil.
This makes the oil hot and burning splash around, mixing it with the air. Now, then the oil was in e.g. a pan, it could only burn where the surface met the air. Now, a lot more hot oil is touching air, causing it to burn faster.
Grease fires burn more when water is added, because:
Burning grease is hotter than the boiling point of water.
Grease is less dense than water.
It’s the grease vapor that burns, and the vapor is emitted from the surface of the grease.
So when water is added, it sinks through the grease and turns into steam underneath it, expands violently and transforms the grease puddle into a shower of grease droplets. The surface area of the droplets is massive, so you suddenly have a bigass expanding cloud of burning grease vapor.
In an oil fire the water turns to steam and the steam expands very fast. This turns some of the oil into little droplets with more access to oxygen thus being able to burn faster.
In a magnesium fire for example the magnesium can react directly and very violently with water and produces hydrogen which then also will react with oxygen which makes it burn even more.
Water in oil is a example of it. The reason is oil I less dense then oil so the water will sink below the oil.
The boiling temperature of oil is also higher then water. So the water can vey quickly start to boil violently . Water expand by a factor 1000 when it turn from a liquid to a gas, so oil will be throw up into the air.
A liquid just burn on the surface where they is oxygen. The surface are of all the drops thrown up in the air is large and more of it can burn at the same time.
If you would physically throw the oil up in the air the same thing would occur.
This is not way it can happen , some chemical reaction will require water to occure. Like Alkali metal where the rect with the oxygen in the water and hydrogen that can burn is released
So: water hits the grease fire and sinks underneath the burning grease.
Then the water damn-near instantly boils because the fire is far hotter than water’s boiling point.
Then the boiling water turns to gas and bubbles up and the bubbles pop. Which means it’s bubbling up into the burning grease. Which sends the burning grease splattering everywhere.
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The water boils making steam. The steam flies up taking flammable liquid with it. The spray of flammable liquid catches fire.
Some fires can provide their own fuel through the decomposition of other materials.
For example, a lithium battery fire produces oxygen as it burns, so it is self fuelling and smothering it with water is not an effective way to put it out. Lithium is also highly reactive with water, so the water itself may act as an accelerant and make the reaction more violent.
In addition, most lithium fires involve electrical systems, and (although water is not a great conductor), it is possible to be shocked or electrocuted if the voltage is high enough or if there are impurities in the water and it is able to conduct through it to the person fighting the fire.
Oils still burns…even on water,
water displaces oil causing the oil to spread thus the fire spreads as a result of the water displacement
You are probably thinking of burning alkaline metals, like lithium.
Those metal react to water and burn or even explode.
Sometimes even moisture in the air is enough to make them react and catch fire.
So throwing water on something reacting with water gives them even more material to react with.
Normally, putting water on a fire either smothers it from oxygen, or cools it down enough to stop the fire.
With grease fires, that doesn’t happen.
Water is denser than grease, so it sinks below the grease. As it takes in heat, it boils. When it boils, you have a pocket of gas under the liquid grease. It throws flaming grease in all directions as it expands up and pushes out. This causes a grease fire to spread.
Say you have some hot burning oil.
You pour in water. But the water is heavier than the oil, so it flows down into the oil. Here, it heats up, rapidly, and turns to steam which bubbles up through the oil.
This makes the oil hot and burning splash around, mixing it with the air. Now, then the oil was in e.g. a pan, it could only burn where the surface met the air. Now, a lot more hot oil is touching air, causing it to burn faster.
Grease fires burn more when water is added, because:
So when water is added, it sinks through the grease and turns into steam underneath it, expands violently and transforms the grease puddle into a shower of grease droplets. The surface area of the droplets is massive, so you suddenly have a bigass expanding cloud of burning grease vapor.
Depends on what is burning.
In an oil fire the water turns to steam and the steam expands very fast. This turns some of the oil into little droplets with more access to oxygen thus being able to burn faster.
In a magnesium fire for example the magnesium can react directly and very violently with water and produces hydrogen which then also will react with oxygen which makes it burn even more.
Water in oil is a example of it. The reason is oil I less dense then oil so the water will sink below the oil.
The boiling temperature of oil is also higher then water. So the water can vey quickly start to boil violently . Water expand by a factor 1000 when it turn from a liquid to a gas, so oil will be throw up into the air.
A liquid just burn on the surface where they is oxygen. The surface are of all the drops thrown up in the air is large and more of it can burn at the same time.
If you would physically throw the oil up in the air the same thing would occur.
This is not way it can happen , some chemical reaction will require water to occure. Like Alkali metal where the rect with the oxygen in the water and hydrogen that can burn is released
It’s a combination of:
Water boils at 212F.
Grease fires burn at over 400F.
Grease floats on top of water.
So: water hits the grease fire and sinks underneath the burning grease.
Then the water damn-near instantly boils because the fire is far hotter than water’s boiling point.
Then the boiling water turns to gas and bubbles up and the bubbles pop. Which means it’s bubbling up into the burning grease. Which sends the burning grease splattering everywhere.
While it’s still burning.
Oops.