G3 - Gas Technician Level 3 Properties of Fuel Gases Questions and Answers

Question 1

A gas technician is investigating a reported gas odor in the basement of a residence. Which property of propane (LPG) is most critical to consider in this scenario?

Accepted Answer

Its specific gravity is greater than air, causing it to accumulate in low areas.

Answer

It has a high heating value of approximately 2,500 BTU/ft³.

Answer

It is colorless and odorless in its natural state.

Answer

Its ignition temperature is higher than that of natural gas.

Question 2

Which of the following statements accurately compares the heating value of natural gas and propane?

Accepted Answer

Propane has a significantly higher heating value per cubic foot than natural gas.

Answer

Natural gas and propane have nearly identical heating values per cubic foot.

Answer

Natural gas has a higher heating value per cubic foot than propane.

Answer

Propane has a heating value of approximately 1,000 BTU per cubic foot.

Question 3

Incomplete combustion of a hydrocarbon fuel, such as natural gas or propane, occurs due to insufficient oxygen. What is the primary toxic gas produced as a result?

Accepted Answer

Carbon Monoxide (CO)

Answer

Carbon Dioxide (CO2)

Answer

Sulfur Dioxide (SO2)

Answer

Nitrogen Dioxide (NO2)

Question 4

The 'flammable range' or 'explosive limits' of a fuel gas refers to the concentration of gas in a gas-air mixture that will support combustion. What defines the Lower Explosive Limit (LEL)?

Accepted Answer

The minimum concentration of gas in air that will burn.

Answer

The maximum concentration of gas in air that will burn.

Answer

The ideal concentration of gas in air for perfect combustion.

Answer

The temperature at which the gas will auto-ignite.

Question 5

A technician is converting a furnace from natural gas to propane. What fundamental property difference requires the technician to change the orifices?

Accepted Answer

Propane has a higher heating value and requires a different air-to-gas ratio.

Answer

Propane is lighter than air.

Answer

Propane has a lower ignition temperature.

Answer

Natural gas is more corrosive to brass components.

Question 6

What is the specific gravity (or relative density) of a gas a measure of?

Accepted Answer

The ratio of the gas's density to the density of air.

Answer

The energy content of the gas per cubic foot.

Answer

The pressure at which the gas liquefies.

Answer

The auto-ignition temperature of the gas.