Unlike British carriers, whose aviation fuel was stored in separate cylinders or coffer-dams surrounded by seawater, all pre-war Japanese carriers had their aviation fuel tanks built integral with the ship's hull and "Shōkaku" was no exception. The dangers this posed, however, did not become evident until wartime experience demonstrated these were often prone to cracking and leaking as the shocks and stresses of hits or near-misses to the carrier's hull were inevitably transferred to and absorbed by the fuel tanks. Following the debacle at Midway in mid-1942, the empty air spaces around "Shōkaku"s aviation fuel tanks, normally pumped full of inert carbon dioxide, were instead filled with concrete in an attempt to protect them from possible damage. But this did little to prevent volatile fumes spreading to the hangar decks in the event damage did occur, particularly demonstrated when "Cavalla" torpedoed and sank her. "Shōkaku" normally stowed 150,000 gallons of avgas for operational use.