hagopbul said:
Could smoke shells for example the ones used by the artillery reduce the concentration of oxygen in the fire zone or making it harder for fire to spread reducing its spreading and easing its extinguish? Is there possibility of harming people nearby, or make it harder to rescue people ?
Apparently, depleting oxygen from the normal 21% to about 15% is enough to prevent fires from starting. This is not a viable idea for fighting wild fires, however.
It would take an extremely large supply of ordinance. Try calculating how much oxygen there is in one square mile of atmosphere up to a height of 100 feet. I get about 42 million pounds. Even if we only have to deplete about 1/3 of that, that's still 14 million pounds per square mile.
Then in any sort of wind, the beneficial effect would be blown downwind. You would have only a few minutes before your one square mile of depleted atmosphere would be one mile downwind. And stirred up to a height of 200 feet.
We already have aircraft flying, delivering actual fire retardant chemicals. Having them drop smoke bombs instead would be rather silly.
Let's do a back of the envelope calculation for heat production...
Normal air is about one ounce per cubic foot (handy number to memorize). If we have a one square foot column, 100 feet in height, that's about 78 ounces of nitrogen, 21 ounces of oxygen and one ounce of everything else. We want to deplete six ounces of that oxygen, reducing it to 15 ounces in our square foot.
Coal is about 12,000 BTU per pound. 12 units of coal (C) will turn 32 units of oxygen (O2) into carbon dioxide (CO2). We have only 6 ounces of oxygen, so we'll need only 2.25 ounces of coal. That amounts to about 1600 BTU. That is enough heat to raise one pound of water by 1600 degrees Fahrenheit.
We are going to end up with a pretty toasty square mile of real estate. If it was not on fire before, it will certainly be blazing afterward.
Generally speaking, the guys working at specialized professions such as fire fighting are pretty good at what they do.