Its a gas gas gas.

On Saturday one of my sisters friends had with them what they claimed was a dispenser for Nitrous Oxide, Laughing Gas in normal terms, and I thought he was having us on.

He filled up a balloon with this gas dispenser and proceeeded to breath in and out of this balloon and once he had stopped he started giggling uncontrolably. You can buy these kits form quite a few places, Boss of Nos, being the particular one this was bought from, with the kits including a dispenser, gas cartridges and balloons. The idea is to fill the balloon up with gas and only breath the air in it, recycling it back and forth, which causes you to get the maximum use of the gas. I'm sure this involves a little bit of asphyxiation as you are limited with oxygen which contributes to the effects felt (although N2O actually has more oxygen in it than atmospheric air).

I tried it and I must admit that a bit of 'normal' air got into my breathing as I wasn't quite sure how to do it, but once I'd finished off the balloon I did feel odd, and yes I did start laughing, with other symptoms being 'funny feeling hands'. Within a minute or so it had worn off but I'm sure if I did it again then I'd be better and breath in the gas properly.

I am also sure that there is still some kind of placebo effect as you can't help but laugh when others are watching you and maybe act up a little, but the gas certainly had an effect.

These dispensers were originally used for making whipped cream, where the Nitrous Oxide whould be mixed with the cream as it leaves the nozzle to produce four times the amount of whipped cream, or you can use no cream, stick a balloon on the end, and have a bit of fun.

For note, I checked up on Wikipedia to learn a little bit more, and maybe it isn't completely clean fun:

The recreational use of nitrous oxide is restricted in many districts of theUnited States. In California, for instance, inhalation of nitrous oxide "for the purpose of causing euphoria, or for the purpose of changing in any manner one’s mental processes," is a criminal offense under its criminal code (Cal. Pen.Code, Sec. 381b).

It can also not be completely good for you:

Nitrouse oxide can be habit-forming, mainly because of its short-lived effect(generally from 1 - 5 minutes in recreational doses) and ease of access. Death can result if it is inhaled in such a way that not enough oxygen is breathed in. While the pure gas is not toxic, long-term use in very large quantities has been associated with dangerous symptoms similar to vitamin B12 deficiency: anemia due to reduced hemopoiesis, neuropathy, tinnitus, and numbness in extremities. Pregnant women should not use nitrous oxide, because chronic use is also
teratogenic and foetotoxic

Worth a laugh though eh? (Read here for an article about N2O in UK Clubland). Most of the pages you'll find seem to be against it's abuse, and I agree that some weak-willed persons may get addicted to it, but isn't that the truth with everything?