Section 11 of the NSW model by-laws says this:
11 Storage of inflammable liquids and other substances and materials
(1) An owner or occupier of a lot must not, except with the prior written approval of the owners corporation, use or store on the lot or on the common property any inflammable chemical, liquid or gas or other inflammable material.
(2) This by-law does not apply to chemicals, liquids, gases or other material used or intended to be used for domestic purposes, or any chemical, liquid, gas or other material in a fuel tank of a motor vehicle or internal combustion engine.
The key, as other have said, is that the container is secure and safe.