CFESA- Gas- EXAM Questions with
100% Correct Answers | Verified |
Updated (Actual Exam) 2026 Updated.
Where does natural gas come from? - Answer Wells deep in the ground
Where does LP gas come from? - Answer byproduct of crude oil, and some is from natural gas
pockets
What are the three different gases often termed as LP gas? - Answer butane, ethane, propane
Are LP tanks filled with gas or liquid? - Answer Liquid
What happens in a LP tank as gas is drawn off? - Answer The liquid boils off and creates
additional gas.
Does natural gas have any odor? - Answer No, not when it comes from the ground and is
cleaned
What is meant by the "specific gravity" of as gas? - Answer the weight of gas compared to the
weight of air
Is natural gas heavier or lighter than air? - Answer Lighter
Is LP gas heavier or lighter than air? - Answer Heavier
Why is LP gas more dangerous to work with than natural gas? - 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? - Answer Approx. 1000 Btu/cu. ft.
Varies from 950 to 1150 btus
What is the heating value for LP gas? - Answer 2500 Btu/cu. ft.
How should you check for gas leaks? - Answer Soap bubbles or electronic leak detector
,Which gas is more volatile, natural or LP gas? Why? - 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? - Answer fuel, oxygen, heat
What are the 3 byproducts of complete combustion? - Answer Nitrogen, carbon dioxide, water
vapor
One cubic foot of natural gas requires how much air to burn? - Answer minimum of 10
How much byproducts are left after burning one cubic foot of natural or LP gas? - Answer 25
What are the dangerous byproducts of that can be left after incomplete combustion? - Answer
carbon monoxide, aldehydes, and hydrogen
Why is carbon monoxide so dangerous? - Answer colorless and odorless
What are aldehydes? - Answer byproducts of incomplete combustion that has a pungent odor
If carbon monoxide is being produced, will there be aldehydes? - Answer No, not always
If there are aldehydes, is there carbon monoxide present? - Answer yes
What determines how much carbon dioxide your blood absorbs? - Answer the concentration
in air, and exposure length
What is primary air? - Answer Air that enters through the burner venturi.
What is secondary air? - Answer Air surrounding the burner, the air in the room
How is primary air controlled? - Answer Air shutters at the inlet of the burner.
What is the hottest part of a flame? - Answer light blue outer cone
What causes flames to lift off of a burner and maintain their shape? - Answer excessive gas
pressure or primary air
, What causes flames with yellow tips? - Answer Insufficient primary air
What causes an almost totally yellow flame? - Answer No primary air
What causes a shapeless flame to flow totally off of the burner? - Answer lack of secondary air
In a confined space, combustion air openings must be located where? - Answer 12in from the
floor and 12in from the ceiling
The minimum area allowed for a fresh air opening is what size? - Answer 100 sq inches
A confined space connected to an unconfined space requires the combustion air opening of one
square inch for every _____ Btus? - Answer 1000, with a minimum of 100sq in
A combustion air opening to the outside must be one square inch for every _____ Btus if open
directly to the outside, or by vertical duct? - Answer 4000
If horizontal ducts are used to bring in fresh air, the size must be one square inch for every
_____ Btus? - Answer 2000
All outside combustion air opening must be protected with what? - Answer Screen, not
smaller than 1/4mesh
What is the difference between a vent and a flue? - Answer A flue removes byproducts from
the combustion chamber, a vent removes byproducts from the room to the outdoors
What are the two primary functions of the flue? - Answer Remove combustion byproducts,
and create a draft to pull in secondary air
How critical is the sizing of the flue? Why? - Answer Very, too small and it will not remove all
the byproducts, too large and the vapors condense
Can a vent pipe be connected directly to the flue on a piece of gas equipment? - Answer NO
What is the function of a draft hood? - Answer To allow flue to determine the draft
100% Correct Answers | Verified |
Updated (Actual Exam) 2026 Updated.
Where does natural gas come from? - Answer Wells deep in the ground
Where does LP gas come from? - Answer byproduct of crude oil, and some is from natural gas
pockets
What are the three different gases often termed as LP gas? - Answer butane, ethane, propane
Are LP tanks filled with gas or liquid? - Answer Liquid
What happens in a LP tank as gas is drawn off? - Answer The liquid boils off and creates
additional gas.
Does natural gas have any odor? - Answer No, not when it comes from the ground and is
cleaned
What is meant by the "specific gravity" of as gas? - Answer the weight of gas compared to the
weight of air
Is natural gas heavier or lighter than air? - Answer Lighter
Is LP gas heavier or lighter than air? - Answer Heavier
Why is LP gas more dangerous to work with than natural gas? - 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? - Answer Approx. 1000 Btu/cu. ft.
Varies from 950 to 1150 btus
What is the heating value for LP gas? - Answer 2500 Btu/cu. ft.
How should you check for gas leaks? - Answer Soap bubbles or electronic leak detector
,Which gas is more volatile, natural or LP gas? Why? - 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? - Answer fuel, oxygen, heat
What are the 3 byproducts of complete combustion? - Answer Nitrogen, carbon dioxide, water
vapor
One cubic foot of natural gas requires how much air to burn? - Answer minimum of 10
How much byproducts are left after burning one cubic foot of natural or LP gas? - Answer 25
What are the dangerous byproducts of that can be left after incomplete combustion? - Answer
carbon monoxide, aldehydes, and hydrogen
Why is carbon monoxide so dangerous? - Answer colorless and odorless
What are aldehydes? - Answer byproducts of incomplete combustion that has a pungent odor
If carbon monoxide is being produced, will there be aldehydes? - Answer No, not always
If there are aldehydes, is there carbon monoxide present? - Answer yes
What determines how much carbon dioxide your blood absorbs? - Answer the concentration
in air, and exposure length
What is primary air? - Answer Air that enters through the burner venturi.
What is secondary air? - Answer Air surrounding the burner, the air in the room
How is primary air controlled? - Answer Air shutters at the inlet of the burner.
What is the hottest part of a flame? - Answer light blue outer cone
What causes flames to lift off of a burner and maintain their shape? - Answer excessive gas
pressure or primary air
, What causes flames with yellow tips? - Answer Insufficient primary air
What causes an almost totally yellow flame? - Answer No primary air
What causes a shapeless flame to flow totally off of the burner? - Answer lack of secondary air
In a confined space, combustion air openings must be located where? - Answer 12in from the
floor and 12in from the ceiling
The minimum area allowed for a fresh air opening is what size? - Answer 100 sq inches
A confined space connected to an unconfined space requires the combustion air opening of one
square inch for every _____ Btus? - Answer 1000, with a minimum of 100sq in
A combustion air opening to the outside must be one square inch for every _____ Btus if open
directly to the outside, or by vertical duct? - Answer 4000
If horizontal ducts are used to bring in fresh air, the size must be one square inch for every
_____ Btus? - Answer 2000
All outside combustion air opening must be protected with what? - Answer Screen, not
smaller than 1/4mesh
What is the difference between a vent and a flue? - Answer A flue removes byproducts from
the combustion chamber, a vent removes byproducts from the room to the outdoors
What are the two primary functions of the flue? - Answer Remove combustion byproducts,
and create a draft to pull in secondary air
How critical is the sizing of the flue? Why? - Answer Very, too small and it will not remove all
the byproducts, too large and the vapors condense
Can a vent pipe be connected directly to the flue on a piece of gas equipment? - Answer NO
What is the function of a draft hood? - Answer To allow flue to determine the draft
