Manufactured with 4-hour fire-rated and weatherproof construction, each locker has an FM-approved fire-rated wall and roof design. Multiple layers of fire-resistant gypsum wallboard are encased between exterior heavy gauge steel and interior galvannealed sheet steel for maximum durability. A leakproof, all welded sump provides compliant secondary containment of hazardous liquids. Galvanized steel grate flooring removes easily for cleaning.