Any home made tricks to fill up a baloon that floats? These days there are a number of fancy balloons available, some of them are very beautiful. As always, they loose their gas overtime and don't rise anymore.

Some of those new type balloons appear to have been made of plastic and are quite easily re-usable but then you can't be going to the balloon guy every time you want a refill.

Are there any home made techniques that can let you fill those up (so they float again) and which generate a gas which is safe to handle at home without any protective gear? 

P.S: This question is not motivated by any urge to save extra money, it's just that I find so many of them lying at home useless when they can be filled up again. Looking for something that's simple to make if possible.
There are some options, not all easily available or safe: Helium is the most used and it most certainly makes them float, being safe at the safe time. However, it's not an home-made trick. Methane is more easily available (in many cities, methane is piped into homes for domestic heating and cooking purposes) but it's very unsafe for such an use, as it could explode. Hot air is also used (think of hot-air balloons) but I wouldn't know how to make it last for a long time as the air would cool down to room temperature very quickly. Lastly, there's hydrogen which could also be produced with some reagents available at home, but it's as dangerous as methane.