You are probably referring to fuel-air explosion weapons. They distribute a cloud of combustible agent (fuel) into the air, and then ignite it. The result is what is called a deflagration, not a detonation, but the rest of us would cheerfully call it an explosion (think of inside of an automobile cylinder head). So powerful that the expanding gas overexpands a little bit against the surrounding atmosphere, drawing a partial vacuum. But it all comes rushing back in. I believe I have seen them at work as warheads for the TOS-1 "flamethrower" artillery rocket. Still, nothing to compare to even a small nuclear warhead.

You are probably referring to fuel-air explosion weapons. They distribute a cloud of combustible agent (fuel) into the air, and then ignite it. The result is what is called a deflagration, not a detonation, but the rest of us would cheerfully call it an explosion (think of inside of an automobile cylinder head). So powerful that the expanding gas overexpands a little bit against the surrounding atmosphere, drawing a partial vacuum. But it all comes rushing back in. I believe I have seen them at work as warheads for the TOS-1 "flamethrower" artillery rocket.