Abstract HVAC (heating, ventilating, and air conditioning) failures occur mainly in chillers, service water systems, cooling towers, evaporative condensers, chilled-water systems, hot-water heating systems and steam boilers. Failures are caused by a variety of mechanisms including oxygen corrosion, tuberculation, dealloying, erosion, underdeposit attack, stress corrosion, corrosion fatigue, acid wastage, manufacturing defects, improper chemical treatment, and galvanic cells. Attack mechanisms are described and appropriate case histories given with specific emphasis on heating, ventilating and air conditioning systems.