No (fire extinguishers)

If you turn it upside down (it has a feed tube that runs to the bottom) and press the handle just very slightly, you can release the pressure without the dry powder coming out. Do it outside, cause you'll still get a trickle of dust but its minimal. Once the pressure is off you just unscrew the top. Pour the powder out and you're done. The powder could be re-used, I take it to the fire station and we put it in zip lock baggies, to toss down chimneys during flue fires.

If you breathe the dust you'll think you're dying, but it really wont hurt you, its just salt. I've eaten plenty as a fireman, and now as a fire inspector.