CFESA Gas UPDATED ACTUAL Exam
Questions and CORRECT Answers
Where does natural gas come from? - CORRECT ANSWER - Wells deep in the ground
Where does LP gas come from? - CORRECT ANSWER - byproduct of crude oil, and
some is from natural gas pockets
What are the three different gases often termed as LP gas? - CORRECT ANSWER -
butane, ethane, propane
Are LP tanks filled with gas or liquid? - CORRECT ANSWER - Liquid
What happens in a LP tank as gas is drawn off? - CORRECT ANSWER - The liquid boils
off and creates additional gas.
Does natural gas have any odor? - CORRECT ANSWER - No, not when it comes from the
ground and is cleaned
What is meant by the "specific gravity" of as gas? - CORRECT ANSWER - the weight of
gas compared to the weight of air
Is natural gas heavier or lighter than air? - CORRECT ANSWER - Lighter
Is LP gas heavier or lighter than air? - CORRECT ANSWER - Heavier
Why is LP gas more dangerous to work with than natural gas? - CORRECT ANSWER -
LP is heavier than air so it does not dissipate, and is more volatile
,What is the heating value of a cubic foot of natural gas? - CORRECT ANSWER - Approx.
1000 Btu/cu. ft. Varies from 950 to 1150 btus
What is the heating value for LP gas? - CORRECT ANSWER - 2500 Btu/cu. ft.
How should you check for gas leaks? - CORRECT ANSWER - Soap bubbles or electronic
leak detector
Which gas is more volatile, natural or LP gas? Why? - CORRECT ANSWER - LP, it has a
higher Btu rating per cubic foot, and is heavier than air so it does not dissipate.
What are 3 things needed for combustion? - CORRECT ANSWER - fuel, oxygen, heat
What are the 3 byproducts of complete combustion? - CORRECT ANSWER - Nitrogen,
carbon dioxide, water vapor
One cubic foot of natural gas requires how much air to burn? - CORRECT ANSWER -
minimum of 10
How much byproducts are left after burning one cubic foot of natural or LP gas? - CORRECT
ANSWER - 25
What are the dangerous byproducts of that can be left after incomplete combustion? - CORRECT
ANSWER - carbon monoxide, aldehydes, and hydrogen
Why is carbon monoxide so dangerous? - CORRECT ANSWER - colorless and odorless
What are aldehydes? - CORRECT ANSWER - byproducts of incomplete combustion that
has a pungent odor
, If carbon monoxide is being produced, will there be aldehydes? - CORRECT ANSWER -
No, not always
If there are aldehydes, is there carbon monoxide present? - CORRECT ANSWER - yes
What determines how much carbon dioxide your blood absorbs? - CORRECT ANSWER -
the concentration in air, and exposure length
What is primary air? - CORRECT ANSWER - Air that enters through the burner venturi.
What is secondary air? - CORRECT ANSWER - Air surrounding the burner, the air in the
room
How is primary air controlled? - CORRECT ANSWER - Air shutters at the inlet of the
burner.
What is the hottest part of a flame? - CORRECT ANSWER - light blue outer cone
What causes flames to lift off of a burner and maintain their shape? - CORRECT
ANSWER - excessive gas pressure or primary air
What causes flames with yellow tips? - CORRECT ANSWER - Insufficient primary air
What causes an almost totally yellow flame? - CORRECT ANSWER - No primary air
What causes a shapeless flame to flow totally off of the burner? - CORRECT ANSWER -
lack of secondary air
Questions and CORRECT Answers
Where does natural gas come from? - CORRECT ANSWER - Wells deep in the ground
Where does LP gas come from? - CORRECT ANSWER - byproduct of crude oil, and
some is from natural gas pockets
What are the three different gases often termed as LP gas? - CORRECT ANSWER -
butane, ethane, propane
Are LP tanks filled with gas or liquid? - CORRECT ANSWER - Liquid
What happens in a LP tank as gas is drawn off? - CORRECT ANSWER - The liquid boils
off and creates additional gas.
Does natural gas have any odor? - CORRECT ANSWER - No, not when it comes from the
ground and is cleaned
What is meant by the "specific gravity" of as gas? - CORRECT ANSWER - the weight of
gas compared to the weight of air
Is natural gas heavier or lighter than air? - CORRECT ANSWER - Lighter
Is LP gas heavier or lighter than air? - CORRECT ANSWER - Heavier
Why is LP gas more dangerous to work with than natural gas? - CORRECT ANSWER -
LP is heavier than air so it does not dissipate, and is more volatile
,What is the heating value of a cubic foot of natural gas? - CORRECT ANSWER - Approx.
1000 Btu/cu. ft. Varies from 950 to 1150 btus
What is the heating value for LP gas? - CORRECT ANSWER - 2500 Btu/cu. ft.
How should you check for gas leaks? - CORRECT ANSWER - Soap bubbles or electronic
leak detector
Which gas is more volatile, natural or LP gas? Why? - CORRECT ANSWER - LP, it has a
higher Btu rating per cubic foot, and is heavier than air so it does not dissipate.
What are 3 things needed for combustion? - CORRECT ANSWER - fuel, oxygen, heat
What are the 3 byproducts of complete combustion? - CORRECT ANSWER - Nitrogen,
carbon dioxide, water vapor
One cubic foot of natural gas requires how much air to burn? - CORRECT ANSWER -
minimum of 10
How much byproducts are left after burning one cubic foot of natural or LP gas? - CORRECT
ANSWER - 25
What are the dangerous byproducts of that can be left after incomplete combustion? - CORRECT
ANSWER - carbon monoxide, aldehydes, and hydrogen
Why is carbon monoxide so dangerous? - CORRECT ANSWER - colorless and odorless
What are aldehydes? - CORRECT ANSWER - byproducts of incomplete combustion that
has a pungent odor
, If carbon monoxide is being produced, will there be aldehydes? - CORRECT ANSWER -
No, not always
If there are aldehydes, is there carbon monoxide present? - CORRECT ANSWER - yes
What determines how much carbon dioxide your blood absorbs? - CORRECT ANSWER -
the concentration in air, and exposure length
What is primary air? - CORRECT ANSWER - Air that enters through the burner venturi.
What is secondary air? - CORRECT ANSWER - Air surrounding the burner, the air in the
room
How is primary air controlled? - CORRECT ANSWER - Air shutters at the inlet of the
burner.
What is the hottest part of a flame? - CORRECT ANSWER - light blue outer cone
What causes flames to lift off of a burner and maintain their shape? - CORRECT
ANSWER - excessive gas pressure or primary air
What causes flames with yellow tips? - CORRECT ANSWER - Insufficient primary air
What causes an almost totally yellow flame? - CORRECT ANSWER - No primary air
What causes a shapeless flame to flow totally off of the burner? - CORRECT ANSWER -
lack of secondary air
