The heat content of natural gas varies from 950 Btu to 1050 ___.

___ is the placement of a device on an energy-isolating device, in accordance with an established procedure, ensuring that the energy-isolating device and the equipment being controlled cannot be operated.

___ pumps are often used as fuel-oil pumps and as pumps to add water treatment chemicals to a boiler.

___ added to boiler water are used to turn scale-forming salts into a nonadhering sludge that stays in suspension in the boiler water.

A therm is equivalent to 100,000 Btu.

The most recent amendments to the Clean Air Act occurred in 1997.

The range of pressure on a vacuum switch on a vacuum pump is usually 2″ Hg to 8″ Hg.

A photocell sensor senses ___ light.

An outside-stem-and-yoke valve is a ___ valve that indicates whether it is open or closed by the position of the stem.

An outside-stem-and-yoke valve is a ___ valve that indicates whether it is open or closed by the position of the stem.