Okay, just a heads-up before I begin explaining this: this is not going to work for many of you. Why, you might ask? It involves household items... for an asthmatic. I know that not everyone here will be able to get metered-dose inhalers the way an asthmatic can. So, if you're asthmatic or have a friend/relative/bdsm-slave who is, start saving your/their discarded inhalers. Come up with something if you have to obtain them from someone else. Get creative.
Even when the meter reaches zero, inhalers still have quite a bit of aerosol left in them. Ever heard the story about the guy who died because he was barbecuing with an inhaler in his breast pocket, just slightly too close to the fire? It exploded and the force was enough to kill him. Yeah, those things can pack a punch.
Anyway, you should try to save the cap as well, to make things easier.
REQUIRED ITEMS:
1. An inhaler
2. Kerosene/lighter fluid
3. Toilet paper
4. Cotton balls
5. Matches
STEP ONE: Rip up some cotton balls, soak them in kerosene or lighter fluid, and stuff them tightly in the open space around the aerosol container as well as the area near the mouthpiece under it. Make sure it fits snugly and shit. This might require precision and patience. Let the cotton dry.
STEP TWO: Create a homemade fuse. Although there are alternative methods, I'll explain what I believe to be the easiest way. Take a square of toilet paper and tear it into five or six strips, fold each strip in half lengthwise, and twist at each end to form something resembling a string. Next, use a knife or screwdriver to crush up the heads of anywhere from a half-dozen to a dozen matches. Get it as far down into a powder as you reasonably can.
STEP THREE: Put the ground-up matchheads into a bowl or other container and sprinkle a small amount of water in. Mix them until a thick paste forms. If it does not, add more crushed-up matchheads and try again. Once it has achieved your desired consistency, take your twisted toilet paper squares from the previous step and roll them in it. Make sure each is thoroughly coated, and wait for them to dry as well.
STEP FOUR: Attach the fuse to the inhaler. Make sure it gets far enough inside the cotton. Unless you have a better idea, duct tape works just fine. Provided you still have the cap, you can attach the fuse through the cap itself, drilling or poking a hole through it. I'm not sure if it really matters which end you attach the fuse to, but I've had better luck with the poking-a-hole-in-the-cap method.
If you don't have the cap, feed the fuse through the narrow space on the top of the inhaler and try to get it as deep into the cotton as you can while leaving a reasonable amount of space for the fuse to be lit.
STEP FIVE: Light fuse.
STEP SIX: Run away.