Fire Marshall made the shop get a metal safety cabinet made especially for Flammables & it is inside the building. It was painted bright yellow w/ red warinings & the doors are self closing. It was double wall & has a 'burn time' rating & was designed to direct the eventual combustion/explosion upwards.
Since I'm in an apartment, I keep my Coleman fuel under an inverted 5 gal pail on my porch. Our front faces SW and you do hear the can sides pop in/out as things heat up/cool down. I do keep my Coleman 'road trip' propane grill in a deck box w/ the extra propane cans and the local hoodlems haven't found either.
Back home, dad kept his fuel cans in the shed, a wooden shed w/ vents...