CFESA GAS CERTIFICATION EXAM COMPLETE SET OF
QUESTIONS AND VERIFIED ANSWERS FOR THOROUGH
PREPARATION RECENTLY UPDATED
300 QUESTIONS AND ANSWERS
1. What is the primary safety concern when working with gas equipment?
Gas leaks and potential explosion or fire hazards.
2. What tool is essential for detecting gas leaks? Electronic gas detector or
soap solution for bubble testing.
3. What is the proper procedure when a gas leak is suspected? Shut off gas
supply immediately, ventilate area, no ignition sources, and test with leak
detector.
4. What is the minimum working pressure for natural gas in commercial
applications? Typically 3.5" W.C. (water column) to 14" W.C.
5. What is the BTU content of natural gas per cubic foot? Approximately
1,000 BTU per cubic foot.
6. What is the BTU content of propane per cubic foot? Approximately 2,500
BTU per cubic foot.
7. What does LEL stand for in gas safety? Lower Explosive Limit - the
minimum concentration of gas in air that can ignite.
8. What is the LEL for natural gas? Approximately 5% by volume in air.
9. What is the LEL for propane? Approximately 2.1% by volume in air.
10. What personal protective equipment is required when working on gas
equipment? Safety glasses, appropriate clothing, gas detector, and proper tools.
11. What is the difference between natural gas and propane density?
Natural gas is lighter than air; propane is heavier than air.
,12. Where do natural gas leaks typically accumulate? Near ceiling areas
since natural gas rises.
13. Where do propane leaks typically accumulate? In low areas, basements,
or floor level since propane sinks.
14. What is the proper ventilation requirement for gas equipment?
Adequate combustion air and proper venting of products of combustion.
15. What is the maximum allowable gas pressure drop in a system?
Generally 0.5" W.C. pressure drop from meter to appliance.
16. What type of pipe joint compound should be used on gas connections?
Gas-rated pipe joint compound or thread sealant approved for gas use.
17. What is the minimum pipe size for a gas line serving multiple
appliances? Determined by total BTU load and pressure drop calculations.
18. How often should gas connections be tested for leaks? After any
disconnection/reconnection and during routine maintenance.
19. What is the proper method to shut off gas to an appliance? Close the
manual gas valve at the appliance and the main shutoff if necessary.
20. What documentation is required after gas work? Inspection certificates,
pressure test records, and leak test documentation.
21. What is the purpose of a gas regulator? To reduce and maintain constant
gas pressure to appliances.
22. What happens if a gas regulator fails? Over-pressure or under-pressure
conditions affecting appliance operation and safety.
23. What is the correct way to test gas pressure? Use a manometer connected
to designated test ports.
24. What is combustion air? Air required for proper burning of gas fuel.
25. What is dilution air? Air mixed with flue gases to reduce temperature in
venting systems.
26. What causes incomplete combustion in gas appliances? Insufficient air,
improper air/gas mixture, or blocked heat exchangers.
, 27. What are the products of complete combustion? Carbon dioxide (CO2)
and water vapor (H2O).
28. What are the products of incomplete combustion? Carbon monoxide
(CO), carbon dioxide (CO2), water vapor, and other compounds.
29. Why is carbon monoxide dangerous? It's colorless, odorless, and prevents
oxygen transport in blood.
30. What is the maximum allowable CO level in flue gases? Generally less
than 400 PPM air-free, varies by appliance type.
31. What is flame rollout? When flames extend beyond the combustion
chamber due to blocked venting or insufficient air.
32. What causes yellow flames in gas burners? Insufficient primary air or
contaminated gas supply.
33. What should gas flames look like in proper operation? Blue flames with
minimal yellow tipping.
34. What is flashback in gas burners? When flames burn back into the gas
line or mixing chamber.
35. What causes delayed ignition? Insufficient gas pressure, blocked orifices,
or ignition system problems.
36. What is the purpose of gas appliance venting? To safely remove products
of combustion from the building.
37. What are the different types of gas appliance venting? Natural draft,
mechanical draft, direct vent, and power vent.
38. What is draft in gas appliances? The pressure difference that moves
combustion gases through the venting system.
39. What can cause poor draft in gas appliances? Blocked vents, inadequate
vent sizing, or adverse weather conditions.
40. What is spillage in gas appliances? When combustion products enter the
room instead of exiting through the vent.
41. How do you test for spillage? Use a match or smoke source near the draft
hood after appliance operation.
QUESTIONS AND VERIFIED ANSWERS FOR THOROUGH
PREPARATION RECENTLY UPDATED
300 QUESTIONS AND ANSWERS
1. What is the primary safety concern when working with gas equipment?
Gas leaks and potential explosion or fire hazards.
2. What tool is essential for detecting gas leaks? Electronic gas detector or
soap solution for bubble testing.
3. What is the proper procedure when a gas leak is suspected? Shut off gas
supply immediately, ventilate area, no ignition sources, and test with leak
detector.
4. What is the minimum working pressure for natural gas in commercial
applications? Typically 3.5" W.C. (water column) to 14" W.C.
5. What is the BTU content of natural gas per cubic foot? Approximately
1,000 BTU per cubic foot.
6. What is the BTU content of propane per cubic foot? Approximately 2,500
BTU per cubic foot.
7. What does LEL stand for in gas safety? Lower Explosive Limit - the
minimum concentration of gas in air that can ignite.
8. What is the LEL for natural gas? Approximately 5% by volume in air.
9. What is the LEL for propane? Approximately 2.1% by volume in air.
10. What personal protective equipment is required when working on gas
equipment? Safety glasses, appropriate clothing, gas detector, and proper tools.
11. What is the difference between natural gas and propane density?
Natural gas is lighter than air; propane is heavier than air.
,12. Where do natural gas leaks typically accumulate? Near ceiling areas
since natural gas rises.
13. Where do propane leaks typically accumulate? In low areas, basements,
or floor level since propane sinks.
14. What is the proper ventilation requirement for gas equipment?
Adequate combustion air and proper venting of products of combustion.
15. What is the maximum allowable gas pressure drop in a system?
Generally 0.5" W.C. pressure drop from meter to appliance.
16. What type of pipe joint compound should be used on gas connections?
Gas-rated pipe joint compound or thread sealant approved for gas use.
17. What is the minimum pipe size for a gas line serving multiple
appliances? Determined by total BTU load and pressure drop calculations.
18. How often should gas connections be tested for leaks? After any
disconnection/reconnection and during routine maintenance.
19. What is the proper method to shut off gas to an appliance? Close the
manual gas valve at the appliance and the main shutoff if necessary.
20. What documentation is required after gas work? Inspection certificates,
pressure test records, and leak test documentation.
21. What is the purpose of a gas regulator? To reduce and maintain constant
gas pressure to appliances.
22. What happens if a gas regulator fails? Over-pressure or under-pressure
conditions affecting appliance operation and safety.
23. What is the correct way to test gas pressure? Use a manometer connected
to designated test ports.
24. What is combustion air? Air required for proper burning of gas fuel.
25. What is dilution air? Air mixed with flue gases to reduce temperature in
venting systems.
26. What causes incomplete combustion in gas appliances? Insufficient air,
improper air/gas mixture, or blocked heat exchangers.
, 27. What are the products of complete combustion? Carbon dioxide (CO2)
and water vapor (H2O).
28. What are the products of incomplete combustion? Carbon monoxide
(CO), carbon dioxide (CO2), water vapor, and other compounds.
29. Why is carbon monoxide dangerous? It's colorless, odorless, and prevents
oxygen transport in blood.
30. What is the maximum allowable CO level in flue gases? Generally less
than 400 PPM air-free, varies by appliance type.
31. What is flame rollout? When flames extend beyond the combustion
chamber due to blocked venting or insufficient air.
32. What causes yellow flames in gas burners? Insufficient primary air or
contaminated gas supply.
33. What should gas flames look like in proper operation? Blue flames with
minimal yellow tipping.
34. What is flashback in gas burners? When flames burn back into the gas
line or mixing chamber.
35. What causes delayed ignition? Insufficient gas pressure, blocked orifices,
or ignition system problems.
36. What is the purpose of gas appliance venting? To safely remove products
of combustion from the building.
37. What are the different types of gas appliance venting? Natural draft,
mechanical draft, direct vent, and power vent.
38. What is draft in gas appliances? The pressure difference that moves
combustion gases through the venting system.
39. What can cause poor draft in gas appliances? Blocked vents, inadequate
vent sizing, or adverse weather conditions.
40. What is spillage in gas appliances? When combustion products enter the
room instead of exiting through the vent.
41. How do you test for spillage? Use a match or smoke source near the draft
hood after appliance operation.
