Okay, if you are serious about what you said, i will tell you the most efficient and less painful method:

My Recommended Method is helium.

What you’ll need:

* A tank of helium; helium is widely used to inflate balloons. If the tank holds enough helium to inflate 600 ballons, you’ll have more than enough: that’s 20 big breaths a minute, times 30 minutes.

* A suitable valve; this should be obtained from the same source as the tank. Be careful when opening this valve, as the gas is highly pressurized. Never put your mouth directly on the output nozzle, or serious injury may occur.

* An oxygen mask; this can be obtained from a medical supplier. Note that the mask may be designed to mix the gas with air, in which case you must modify it, so that it supplies 100% gas. This can usually be done with duct tape.

* A four foot length of rubber tubing; this may come with the mask, otherwise try a hardware store. If the tank’s nozzle and the mask inlet have different diameters, try using several different diameters of tubing, each fit within the other, and thoroughly sealed with duct tape.

Instructions:

If you’re indoors, open all available windows. Attach the valve to the tank, if it’s not already attached. Now attach one end of the tubing to the valve outlet, and the other end to the mask. Test your connections to make sure nothing leaks. Recline or sit, in such a way that you can’t fall over, for example in bed or on a sofa, propped up with pillows. Strap the mask onto your face, so that your mouth and nose are covered. Turn on the valve, and breathe normally. Your voice will become high-pitched almost immediately, and in few minutes, you will lose consciousness. Within fifteen minutes, you will be dead, due to asphyxiation. Make sure you will not be disturbed for at least thirty minutes, just to be sure.

F.A.Q.:

1. A 600-ballon tank is hard to find and/or too heavy, will a 400-balloon tank work?

400 balloons is somewhere between 400 and 800 breaths of helium, depending on the balloon size and your lung capacity. You might want to see how many breaths it takes for you to blow up a balloon, which will give you a better estimate of your capacity. You also need to know how many breaths you take per minute, so time yourself with a wristwatch. Of course this depends on your physical and emotional state: for example if you’re upset you’ll breathe faster. Let’s say you find that it takes you 1.5 breaths to fill up a balloon, and that you take 20 breaths a minute when reasonably relaxed. So:

400 * 1.5 = 600 breaths in the tank.

600 / 20 = 30 minutes.

30 minutes without *any* oxygen would definitely kill you. But the problem is, you’ll still be getting some amount of oxygen, because even the best mask doesn’t seal perfectly. Let’s say you’re getting 75% helium:

30 * .75 = 22 minutes.

22 minutes is still enough to do the job, so yes, a 400-balloon tank will work, provided you have a suitable mask that seals well, and provided you don’t waste a lot of helium testing your mask and connections. But there’s very little room for error, and that’s why i recommend a 600-ballon tank: to avoid failure, you want to be absolutely sure you won’t run out of gas.

2. Where can I find a suitable helium tank, and/or an oxygen mask?

I can provide these info, but this is best done in private.