Boilers may be of the steam or hot water type and classified as low or high pressure.
Boilers are regulated by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Code.
Should be equipped with controls and interlocks to shut off the burner or heating elements in the event of low water conditions or predetermined temperatures.
Gravity furnaces operate primarily on circulation of air due to gravity. Mounted on the floor and designed to heat only spaces above them.
Forced warm air furnaces use fans to circulate air through plenums and ductwork.
Automatic controls should be provided on both types to shut off at a predetermined temperature.
Fire problems are principally due to improper clearances, lack of limit controls, heat exchanger burnout, improper installation or maintenance procedures.
