Here are our guidelines on how much gas you can store safely
For residential properties, you can store up to 30kg of butane (2 x 15kg gas bottles) indoors, for use in portable gas heaters for example.
Propane should always be stored outdoors; and in the case of fixed installations, propane should be sited outside. Calor stockists and commercial/industrial premises may use propane indoors on a temporary basis, for example whilst using a blowtorch, but the LPG should be stored outdoors and in accordance with the UKLPG Code of Practice No 7 "Storage of Full and Empty LPG Cylinders and Cartridges".
For more information, please see our "Code of Guidance for the Storage of Cylinders" and "Cylinder Storage Information" PDFs.