Not sure about the tank but I know of a way to get free oxygen, yep that's right..free. PM me if interested (but keep it a secret) ....
Yeah, your free oxygen isn't pure oxygen. The OP is talkin about 95-100% O2, not the 21% in the atmosphere. OP, check out one of Grasscity's competitors located in the UK, they sell em.
come on, what kind of asshole wants a tank of oxygen for no good reason. you think youre better than the rest of us cause youre getting pure O2 OP? huh? do ya?