text: I think you mean a FAE, i.e. Fuel-Air Explosive. \nThey do exist. They are, however, considered "conventional" weapons, even if their destructive power is comparable to small nuclear weapons (so FAE are often called "poor man's nukes"), yet they produce no radioactivity.\n\nHow it works? \nYou take an air-delivery system (usually an air-droppable bomb) and fill it with liquid combustible (specially prepared petrol). Once released, the FAE engages on pre-set altitude, spraying the petrol around it to create a fuel-air mix of greatest efficiency (hence the name), then ignites it. The explosion... as I said, it's comaprable to a nuke.\nAs a side - effect, such an explosion burns out oxygen out of air, what would kill every living organism there (provided it would survive heat and shockwave of the general blast). Of course, after a while the air mixes and becomes breathable again.\n\nNote that it is as destructible to buildings, vehicles and other objects as any explosion of that size would be. So no way of "killing the people, but leaving stuff untouched". \n\nHumanitarity... I'm not sure there's any truly humantarian weapon, maybe except a toy watergun (and you're not going to win a war with these). FAE doesn't seem particulary inhumanitarian way of killing human beings to me, since it leaves no residue Nuclear, Biological and Chemical weapons tend to produce. \nOf course, I have no first-hand experience with the problem...