[MC]

Is there any chemical/substance which can be added to the gasoline and diesel fuel to make them fire resistant (not to be able to burn)?

[The_MD]

Could probably do with you expanding on that a bit.  What do you want to do with the diesel/petrol afterwards? 

[MC]

It is not so important what it is for. It is not important if gasoline/diesel loses their characteristics in the process. I would like to know if there is some chemical which can be added. Anything which comes to your mind is welcomed.

[fledarmus]

The problem is that gasoline and diesel fuel are not single compounds. They are both complex mixtures with carefully defined properties, largely based on their ability to ignite and burn. If it doesn't ignite or burn, then it isn't gasoline or diesel fuel.

So what are you trying to come up with? A mixture with the liquid handling properties of gasoline or diesel but that isn't flammable? An additive that can be put into gasoline or diesel fuel that would stop it from igniting or burning and would render a tankful useless? Something that can be thrown into or over a gasoline or diesel fuel fire that would instantly stop combustion? It is in fact, very important what it is for.  Otherwise, we're just playing "guess what number MC is thinking of". That game gets old before it starts.

[MC]

I think that it is not important use of it (although it is for a quite good purpose). If there is a such chemical or chemicals than I can think about next step. Can you please just say if there is something like that.
Imagine simple scenario:
Tray with small amount of gasoline/diesel. Bottle of "chemical". Pour content of bottle into tray. Take one match and throw it into tray.
Is there bottle of "chemical" which would prevent ignition?

[enahs]

Enough water and dilute the gasoline a whole heck of a lot.
I supposed maybe even enough dry ice thrown in gasoline would develop a layer of CO2 over it, pushing oxygen out of the way and make it a lot less flammable (while the CO2 is there).

[MC]

 No, water and dry ice is not applicable.

[fledarmus]

The problem is that the tray full of gasoline or diesel fuel is not your problem - the gasoline and diesel vapors above the tray are.

You might consider Halon 1301 which is frequently used for fire suppression in areas where water and carbon dioxide can't be used. At concentrations of a few percent in air, the halon decomposes to form halogens which sequester the free radicals responsible for fire propogation, quenching fires even when oxygen, fuel, and heat are still available. In fact, it was injected into fuel-tanks of F-16 fighters encountering unfriendly fire to prevent the vapors from exploding if the tank was hit. See http://en.wikipedia.org/wiki/Halon_1301 for more information. There is a list of other possible solutions in the paragraph headed "Alternatives"

[MC]

Thanks for answers. I have considered fumes which are flamable. Sistem would be closed so potential chemical would be mixed with fumes as well. If there is no such chemical I will consider nitrogen to freeze fuel.