Question Hazardous materials placards are usually shaped like: Answers Circles. Triangles. Diamonds. Explanation Hazardous materials warning placards are usually diamond-shaped. This questions appears in the following tests: Alaska HazMat Connecticut HazMat Delaware HazMat Delaware Tank Florida HazMat Hawaii HazMat Idaho HazMat Iowa HazMat Louisiana HazMat Missouri HazMat New Hampshire Tank New Mexico HazMat New Mexico HazMat North Carolina HazMat Ohio HazMat Oklahoma HazMat Oklahoma HazMat Oklahoma Tank Washington HazMat Washington HazMat Wisconsin HazMat