Does anyone know how to make homemade Co2 thingy

I need some info on making a homemade c02 thing

https://www.rollitup.org/do-yourself/1362-home-made-co2-tutorial.html

check that out, you can find the DIY section under "general marijuana growing"

Heres the link

https://www.rollitup.org/do-yourself/1362-home-made-co2-tutorial.html