1. Q: What is the specific gravity of natural gas? ANSWER Approximately
0.60 (lighter than air, which has a specific gravity of 1.0)
2. Q: What is the specific gravity of propane? ANSWER Approximately
1.52 (heavier than air)
3. Q: What is the BTU content of natural gas per cubic foot? ANSWER
Approximately 1,000 BTU per cubic foot
4. Q: What is the BTU content of propane per cubic foot? ANSWER
Approximately 2,500 BTU per cubic foot
5. Q: What percentage of air is oxygen? ANSWER Approximately 21%
6. Q: What is the ignition temperature of natural gas? ANSWER
Approximately 1,100-1,200°F (593-649°C)
7. Q: What is the ignition temperature of propane? ANSWER
Approximately 920-1,120°F (493-604°C)
8. Q: What does LEL stand for? ANSWER Lower Explosive Limit - the
minimum concentration of gas in air that will ignite
9. Q: What is the LEL for natural gas? ANSWER Approximately 5% (by
volume in air)
10. Q: What is the UEL (Upper Explosive Limit) for natural gas?
ANSWER Approximately 15% (by volume in air)
11. Q: What is the LEL for propane? ANSWER Approximately 2.1% (by
volume in air)
12. Q: What is the UEL for propane? ANSWER Approximately 9.5% (by
volume in air)
13. Q: What is the primary component of natural gas? ANSWER Methane
(CH4)
14. Q: What odorant is commonly added to natural gas? ANSWER
Mercaptan (typically ethyl mercaptan or methyl mercaptan)
,15. Q: Why is odorant added to natural gas? ANSWER Natural gas is
naturally odorless and colorless; odorant is added for leak detection and safety
16. Q: What is the chemical formula for propane? ANSWER C3H8
17. Q: At what concentration can natural gas odorant typically be
detected? ANSWER At approximately 1/5 of the LEL (about 1% gas in air)
18. Q: What is the molecular weight of natural gas (methane)? ANSWER
Approximately 16 (making it lighter than air at 29)
19. Q: What happens to propane in cold temperatures? ANSWER Propane
vaporization slows down; liquid propane may not vaporize adequately below -
44°F
20. Q: What is the vapor pressure of propane at 70°F? ANSWER
Approximately 127 psig
21. Q: What is the boiling point of propane at atmospheric pressure?
ANSWER -44°F (-42°C)
22. Q: What is wobbe index? ANSWER A measure of gas interchangeability;
it's the heating value divided by the square root of specific gravity
23. Q: What is complete combustion? ANSWER Combustion where fuel
burns with sufficient oxygen to produce primarily CO2 and water vapor
24. Q: What is incomplete combustion? ANSWER Combustion with
insufficient oxygen, producing carbon monoxide (CO) and other products
25. Q: What is the primary danger of carbon monoxide? ANSWER It is
odorless, colorless, toxic, and can cause death by preventing oxygen transport in
blood
26. Q: What air-to-gas ratio is needed for complete combustion of natural
gas? ANSWER Approximately 10:1 (10 parts air to 1 part natural gas)
27. Q: What is the typical operating pressure for residential natural gas
service? ANSWER 1/4 psig to 2 psig (7" W.C. to 14" W.C. is common)
28. Q: What does W.C. stand for in gas pressure measurement? ANSWER
Water Column (inches of water column)
29. Q: How many inches of water column equal 1 psi? ANSWER 27.7
inches W.C. = 1 psi
30. Q: What is the typical delivery pressure for propane at an appliance?
ANSWER 11 inches W.C. (approximately 0.4 psi)
, Section 2: Codes and Standards (Questions 31-60)
31. Q: What is the primary code governing gas piping installations in North
America? ANSWER NFPA 54 / National Fuel Gas Code (ANSI Z223.1)
32. Q: What does ANSI stand for? ANSWER American National Standards
Institute
33. Q: What does NFPA stand for? ANSWER National Fire Protection
Association
34. Q: What is CSA B149.1? ANSWER Canadian natural gas and propane
installation code
35. Q: What does AHJ stand for? ANSWER Authority Having Jurisdiction
36. Q: Who is typically the AHJ for gas installations? ANSWER The local
building inspector, fire marshal, or designated official with enforcement
authority
37. Q: What is IFGC? ANSWER International Fuel Gas Code
38. Q: What standard covers gas appliances? ANSWER ANSI Z21 series
standards (now CSA/ANSI standards)
39. Q: What is the minimum burial depth for gas piping in normal
conditions? ANSWER Typically 18 inches, but local codes may vary (12-24
inches depending on location and protection)
40. Q: What is the purpose of a gas permit? ANSWER To ensure
installations comply with codes and are inspected by qualified authorities
41. Q: Are gas piping installations required to be inspected? ANSWER
Yes, by the AHJ before being concealed and put into service
42. Q: What test pressure is required for gas piping systems? ANSWER
Minimum 1.5 times operating pressure for at least 10 minutes, or as specified by
code
43. Q: What is the typical test pressure for residential gas piping?
ANSWER 10-15 psig for systems operating at less than 0.5 psig
44. Q: How long must a pressure test be maintained? ANSWER Minimum
10 minutes to 1 hour depending on code requirements and system pressure
45. Q: What is the maximum allowable pressure drop during testing?
ANSWER Typically no more than 1" W.C. (0.036 psi) or 10% of gauge
reading, whichever is less
0.60 (lighter than air, which has a specific gravity of 1.0)
2. Q: What is the specific gravity of propane? ANSWER Approximately
1.52 (heavier than air)
3. Q: What is the BTU content of natural gas per cubic foot? ANSWER
Approximately 1,000 BTU per cubic foot
4. Q: What is the BTU content of propane per cubic foot? ANSWER
Approximately 2,500 BTU per cubic foot
5. Q: What percentage of air is oxygen? ANSWER Approximately 21%
6. Q: What is the ignition temperature of natural gas? ANSWER
Approximately 1,100-1,200°F (593-649°C)
7. Q: What is the ignition temperature of propane? ANSWER
Approximately 920-1,120°F (493-604°C)
8. Q: What does LEL stand for? ANSWER Lower Explosive Limit - the
minimum concentration of gas in air that will ignite
9. Q: What is the LEL for natural gas? ANSWER Approximately 5% (by
volume in air)
10. Q: What is the UEL (Upper Explosive Limit) for natural gas?
ANSWER Approximately 15% (by volume in air)
11. Q: What is the LEL for propane? ANSWER Approximately 2.1% (by
volume in air)
12. Q: What is the UEL for propane? ANSWER Approximately 9.5% (by
volume in air)
13. Q: What is the primary component of natural gas? ANSWER Methane
(CH4)
14. Q: What odorant is commonly added to natural gas? ANSWER
Mercaptan (typically ethyl mercaptan or methyl mercaptan)
,15. Q: Why is odorant added to natural gas? ANSWER Natural gas is
naturally odorless and colorless; odorant is added for leak detection and safety
16. Q: What is the chemical formula for propane? ANSWER C3H8
17. Q: At what concentration can natural gas odorant typically be
detected? ANSWER At approximately 1/5 of the LEL (about 1% gas in air)
18. Q: What is the molecular weight of natural gas (methane)? ANSWER
Approximately 16 (making it lighter than air at 29)
19. Q: What happens to propane in cold temperatures? ANSWER Propane
vaporization slows down; liquid propane may not vaporize adequately below -
44°F
20. Q: What is the vapor pressure of propane at 70°F? ANSWER
Approximately 127 psig
21. Q: What is the boiling point of propane at atmospheric pressure?
ANSWER -44°F (-42°C)
22. Q: What is wobbe index? ANSWER A measure of gas interchangeability;
it's the heating value divided by the square root of specific gravity
23. Q: What is complete combustion? ANSWER Combustion where fuel
burns with sufficient oxygen to produce primarily CO2 and water vapor
24. Q: What is incomplete combustion? ANSWER Combustion with
insufficient oxygen, producing carbon monoxide (CO) and other products
25. Q: What is the primary danger of carbon monoxide? ANSWER It is
odorless, colorless, toxic, and can cause death by preventing oxygen transport in
blood
26. Q: What air-to-gas ratio is needed for complete combustion of natural
gas? ANSWER Approximately 10:1 (10 parts air to 1 part natural gas)
27. Q: What is the typical operating pressure for residential natural gas
service? ANSWER 1/4 psig to 2 psig (7" W.C. to 14" W.C. is common)
28. Q: What does W.C. stand for in gas pressure measurement? ANSWER
Water Column (inches of water column)
29. Q: How many inches of water column equal 1 psi? ANSWER 27.7
inches W.C. = 1 psi
30. Q: What is the typical delivery pressure for propane at an appliance?
ANSWER 11 inches W.C. (approximately 0.4 psi)
, Section 2: Codes and Standards (Questions 31-60)
31. Q: What is the primary code governing gas piping installations in North
America? ANSWER NFPA 54 / National Fuel Gas Code (ANSI Z223.1)
32. Q: What does ANSI stand for? ANSWER American National Standards
Institute
33. Q: What does NFPA stand for? ANSWER National Fire Protection
Association
34. Q: What is CSA B149.1? ANSWER Canadian natural gas and propane
installation code
35. Q: What does AHJ stand for? ANSWER Authority Having Jurisdiction
36. Q: Who is typically the AHJ for gas installations? ANSWER The local
building inspector, fire marshal, or designated official with enforcement
authority
37. Q: What is IFGC? ANSWER International Fuel Gas Code
38. Q: What standard covers gas appliances? ANSWER ANSI Z21 series
standards (now CSA/ANSI standards)
39. Q: What is the minimum burial depth for gas piping in normal
conditions? ANSWER Typically 18 inches, but local codes may vary (12-24
inches depending on location and protection)
40. Q: What is the purpose of a gas permit? ANSWER To ensure
installations comply with codes and are inspected by qualified authorities
41. Q: Are gas piping installations required to be inspected? ANSWER
Yes, by the AHJ before being concealed and put into service
42. Q: What test pressure is required for gas piping systems? ANSWER
Minimum 1.5 times operating pressure for at least 10 minutes, or as specified by
code
43. Q: What is the typical test pressure for residential gas piping?
ANSWER 10-15 psig for systems operating at less than 0.5 psig
44. Q: How long must a pressure test be maintained? ANSWER Minimum
10 minutes to 1 hour depending on code requirements and system pressure
45. Q: What is the maximum allowable pressure drop during testing?
ANSWER Typically no more than 1" W.C. (0.036 psi) or 10% of gauge
reading, whichever is less
