All gas, oil, and coal-fired boilers and their steam-distribution systems are subject to inefficiencies that prevent the complete transfer of the inherent heat in the fuel. Many of the inefficiency sources cannot be easily controlled. There are three principal corrosion-related causes of heat-loss inefficiency in steam-boiler systems: formation of boiler tube scale, loss of heated steam through leakage, and loss of fuels stored under pressure. These causes of inefficiency can be controlled. The article discusses how these preventable losses take place and methods for evaluating them.