Do we need secondary containment for every IBC or only the hazardous ones?

We're setting up a storage area in our new unit and I'm trying to work out what secondary containment we actually need before we bring stock in. Some of what we store is fairly benign, some of it isn't, and I keep getting different answers from suppliers about whether secondary containment rules for UAE chemicals apply to everything or only the hazardous classifications. The warehouse guy next door said he's never bothered with bunds and has never been pulled up, but I'm not sure that's the standard to aim for. Has anyone here been through a proper inspection and can say what they actually check? And does the volume matter, like does a small IBC need the same containment as a big one?