___ air controls combustion efficiency and is usually introduced into a furnace from below the burner.

If the top line to a gauge glass is closed or clogged, the glass will fill with water.

Relief valves should be manually tested every 30 days as recommended by the ASME Code.

A(n) ___ system is a solid-state control system in which a building automation controller is wired directly to control devices.

A safety valve’s capacity is listed on the data plate attached to the safety valve.

A safety valve’s capacity is listed on the data plate attached to the safety valve.

A gas law relates to events that occur as heat is generated by the combustion of a fuel and is used to produce steam or hot water in a boiler.

A(n) ___ is a heat exchanger used to absorb heat from an area to be cooled and transfer the heat into refrigerant.

An expansion tank moves water from a boiler to a supply line.

Steam is produced as water is heated at its boiling point (212°F at atmospheric pressure).