G33 Master Gas Pipe Fitter Exam
1. The primary purpose of a sediment trap (drip leg) at a gas appliance is to:
a) Regulate the gas pressure to the appliance.
b) Catch moisture and solid debris before they enter the appliance controls.
c) Serve as a shut-off valve for appliance service.
d) Vent excess gas in the event of overpressure.
Answer: B
Explanation: Sediment traps are designed to collect moisture, pipe scale, dirt, and other
solid particles from the gas stream. This prevents these contaminants from fouling the
appliance's gas valves, burners, and controls, which could lead to malfunction or unsafe
operation. They are required at the inlet to every appliance, except for those with listed
self-cleaning traps or illuminated appliances.
2. According to the IFGC, the minimum working clearance in front of an electrical
panel serving a gas-fired furnace must be:
a) 24 inches
b) 30 inches
c) 36 inches
d) 42 inches
Answer: B
Explanation: This question tests knowledge of the intersection between electrical and
gas codes. The NEC (National Electrical Code), which is often cross-referenced, requires
a 30-inch clear working space in front of electrical equipment. A Master Fitter must be
aware of requirements for all systems they interact with.
3. A "lockable" gas shut-off valve is required for which of the following situations?
a) All commercial appliances.
b) Any appliance located in a public assembly area.
c) Any appliance where the shut-off valve is not immediately adjacent to the appliance
and out of sight.
d) Both B and C.
Answer: D
Explanation: The IFGC mandates that the shut-off valve for an appliance must be
located in the same room and within 6 feet. If the valve is not in the same room or is out
,of sight (e.g., in a ceiling plenum or separate closet), it must be lockable. This also
applies to appliances in public areas to prevent unauthorized operation.
4. The smell added to natural gas (mercaptan) is a safety measure designed to
alert occupants at what concentration of gas in air?
a) At the Lower Flammable Limit (LFL)
b) At one-fifth (1/5) of the LFL
c) At the Upper Flammable Limit (UFL)
d) At 1000 PPM
Answer: B
Explanation: Odorants are added to natural gas, which is naturally odorless, to provide
a warning. The odor is intended to be detectable by most people at a concentration of
1/5 the lower flammable limit (which is about 1% gas in air). This provides a significant
safety margin before the gas-air mixture becomes ignitable.
5. Before performing any work on an existing gas line, the first safety step is to:
a) Purge the line with an inert gas.
b) Check for leaks with a combustible gas indicator.
c) Shut off the gas supply at the meter or propane tank.
d) Disconnect the appliance.
Answer: C
Explanation: The most fundamental and critical first step is to positively shut off the gas
supply at its source. All other safety procedures, such as purging and leak checking, are
performed after the supply has been isolated.
6. A "CSST" gas piping system must be:
a) Bonded and grounded to prevent damage from lightning-induced electrical surges.
b) Installed only in exposed locations for easy inspection.
c) Sleeved when run through concrete slabs.
d) Used only for low-pressure applications under 1/2 psi.
Answer: A
Explanation: Corrugated Stainless Steel Tubing (CSST) is susceptible to puncture from
electrical arcing caused by lightning strikes traveling through the building. The
manufacturer's instructions and code require that the CSST system be bonded to the
electrical grounding system to mitigate this risk.
7. When sizing a gas piping system using the longest length method, what is the
purpose of including an "allowance for fittings"?
a) To account for the pressure drop caused by valves and elbows.
,b) To increase the system's overall capacity for future appliances.
c) To ensure the pipe can handle the maximum possible pressure.
d) To meet the minimum code requirement for pipe length.
Answer: A
Explanation: Valves, tees, elbows, and other fittings create resistance to gas flow, which
results in a pressure drop. The "allowance for fittings" is a way of converting this
resistance into an equivalent length of straight pipe, allowing for a more accurate
calculation of the total system pressure drop.
8. A section of pipe needs to deliver 250 CFH of natural gas. It has 5 elbows and 2
tees (branch flow). If the equivalent length for each elbow is 3 ft and for each tee
is 8 ft, what is the total equivalent length added by the fittings?
a) 15 ft
b) 16 ft
c) 31 ft
d) 47 ft
Answer: C
Explanation: Calculation: (5 elbows × 3 ft/elbow) + (2 tees × 8 ft/tee) = 15 ft + 16 ft =
31 ft. This 31 ft would be added to the actual measured length of the pipe run for sizing
purposes.
9. For a given pipe size and length, which gas has a higher volumetric flow rate
(CFH) for the same pressure drop?
a) Natural Gas (0.60 Specific Gravity)
b) Propane Gas (1.50 Specific Gravity)
c) They have the same flow rate.
d) It depends on the BTU content.
Answer: A
Explanation: Gases with a lower specific gravity (lighter than air, like natural gas) will
have a higher flow capacity than heavier gases (like propane) for the same pipe size,
length, and pressure drop. Sizing tables are specific to the type of gas.
10. A 1-inch schedule 40 black iron pipe, 50 feet long, supplying natural gas at a
0.5 psi pressure, has a capacity of approximately 270 CFH. If the load requirement
is 300 CFH, the best solution is to:
a) Increase the inlet pressure to 1.0 psi.
b) Use a 1.25-inch pipe for that section.
c) Use two parallel 3/4-inch pipes.
d) Reduce the length of the pipe run.
, Answer: B
Explanation: The pipe is undersized for the load. The most direct and code-compliant
solution is to upsize the pipe to a size that can deliver the required CFH, which in this
case would be 1.25-inch. Increasing pressure may not be permissible and doesn't
address the root cause. Parallel pipes are complex and rarely used in standard practice.
11. The total connected load for a building is 450,000 BTU/hr. What is the
approximate minimum capacity the gas meter and service line must have?
a) 450 CFH
b) 450 BTU/hr
c) 450 CCF
d) 450 therms
Answer: A
Explanation: For natural gas, a common rough approximation is 1 CFH ≈ 1000 BTU/hr.
Therefore, 450,000 BTU/hr / 1000 BTU/hr per CFH = 450 CFH. The meter and service
must be sized to handle the total connected load, not just the demand load.
12. When sizing a manifold system for a building with multiple apartments, the
diversity factor is applied to:
a) The pipe size for each individual apartment.
b) The pressure drop across the regulator.
c) The total load used to size the main trunk line.
d) The length of the service line from the street.
Answer: C
Explanation: A diversity factor acknowledges that not all appliances in all units will be
operating at peak capacity simultaneously. This allows the main trunk line and meter to
be sized for a "demand load" that is less than the sum of all individual "connected
loads," leading to a more economical design.
13. What is the minimum required coverage for a steel gas pipe buried
underground?
a) 6 inches
b) 12 inches
c) 18 inches
d) 24 inches
Answer: B
Explanation: The IFGC typically requires a minimum cover of 12 inches for steel gas
piping to protect it from physical damage and, in some cases, frost lines. Local codes
may require deeper burial, so they must always be checked.
1. The primary purpose of a sediment trap (drip leg) at a gas appliance is to:
a) Regulate the gas pressure to the appliance.
b) Catch moisture and solid debris before they enter the appliance controls.
c) Serve as a shut-off valve for appliance service.
d) Vent excess gas in the event of overpressure.
Answer: B
Explanation: Sediment traps are designed to collect moisture, pipe scale, dirt, and other
solid particles from the gas stream. This prevents these contaminants from fouling the
appliance's gas valves, burners, and controls, which could lead to malfunction or unsafe
operation. They are required at the inlet to every appliance, except for those with listed
self-cleaning traps or illuminated appliances.
2. According to the IFGC, the minimum working clearance in front of an electrical
panel serving a gas-fired furnace must be:
a) 24 inches
b) 30 inches
c) 36 inches
d) 42 inches
Answer: B
Explanation: This question tests knowledge of the intersection between electrical and
gas codes. The NEC (National Electrical Code), which is often cross-referenced, requires
a 30-inch clear working space in front of electrical equipment. A Master Fitter must be
aware of requirements for all systems they interact with.
3. A "lockable" gas shut-off valve is required for which of the following situations?
a) All commercial appliances.
b) Any appliance located in a public assembly area.
c) Any appliance where the shut-off valve is not immediately adjacent to the appliance
and out of sight.
d) Both B and C.
Answer: D
Explanation: The IFGC mandates that the shut-off valve for an appliance must be
located in the same room and within 6 feet. If the valve is not in the same room or is out
,of sight (e.g., in a ceiling plenum or separate closet), it must be lockable. This also
applies to appliances in public areas to prevent unauthorized operation.
4. The smell added to natural gas (mercaptan) is a safety measure designed to
alert occupants at what concentration of gas in air?
a) At the Lower Flammable Limit (LFL)
b) At one-fifth (1/5) of the LFL
c) At the Upper Flammable Limit (UFL)
d) At 1000 PPM
Answer: B
Explanation: Odorants are added to natural gas, which is naturally odorless, to provide
a warning. The odor is intended to be detectable by most people at a concentration of
1/5 the lower flammable limit (which is about 1% gas in air). This provides a significant
safety margin before the gas-air mixture becomes ignitable.
5. Before performing any work on an existing gas line, the first safety step is to:
a) Purge the line with an inert gas.
b) Check for leaks with a combustible gas indicator.
c) Shut off the gas supply at the meter or propane tank.
d) Disconnect the appliance.
Answer: C
Explanation: The most fundamental and critical first step is to positively shut off the gas
supply at its source. All other safety procedures, such as purging and leak checking, are
performed after the supply has been isolated.
6. A "CSST" gas piping system must be:
a) Bonded and grounded to prevent damage from lightning-induced electrical surges.
b) Installed only in exposed locations for easy inspection.
c) Sleeved when run through concrete slabs.
d) Used only for low-pressure applications under 1/2 psi.
Answer: A
Explanation: Corrugated Stainless Steel Tubing (CSST) is susceptible to puncture from
electrical arcing caused by lightning strikes traveling through the building. The
manufacturer's instructions and code require that the CSST system be bonded to the
electrical grounding system to mitigate this risk.
7. When sizing a gas piping system using the longest length method, what is the
purpose of including an "allowance for fittings"?
a) To account for the pressure drop caused by valves and elbows.
,b) To increase the system's overall capacity for future appliances.
c) To ensure the pipe can handle the maximum possible pressure.
d) To meet the minimum code requirement for pipe length.
Answer: A
Explanation: Valves, tees, elbows, and other fittings create resistance to gas flow, which
results in a pressure drop. The "allowance for fittings" is a way of converting this
resistance into an equivalent length of straight pipe, allowing for a more accurate
calculation of the total system pressure drop.
8. A section of pipe needs to deliver 250 CFH of natural gas. It has 5 elbows and 2
tees (branch flow). If the equivalent length for each elbow is 3 ft and for each tee
is 8 ft, what is the total equivalent length added by the fittings?
a) 15 ft
b) 16 ft
c) 31 ft
d) 47 ft
Answer: C
Explanation: Calculation: (5 elbows × 3 ft/elbow) + (2 tees × 8 ft/tee) = 15 ft + 16 ft =
31 ft. This 31 ft would be added to the actual measured length of the pipe run for sizing
purposes.
9. For a given pipe size and length, which gas has a higher volumetric flow rate
(CFH) for the same pressure drop?
a) Natural Gas (0.60 Specific Gravity)
b) Propane Gas (1.50 Specific Gravity)
c) They have the same flow rate.
d) It depends on the BTU content.
Answer: A
Explanation: Gases with a lower specific gravity (lighter than air, like natural gas) will
have a higher flow capacity than heavier gases (like propane) for the same pipe size,
length, and pressure drop. Sizing tables are specific to the type of gas.
10. A 1-inch schedule 40 black iron pipe, 50 feet long, supplying natural gas at a
0.5 psi pressure, has a capacity of approximately 270 CFH. If the load requirement
is 300 CFH, the best solution is to:
a) Increase the inlet pressure to 1.0 psi.
b) Use a 1.25-inch pipe for that section.
c) Use two parallel 3/4-inch pipes.
d) Reduce the length of the pipe run.
, Answer: B
Explanation: The pipe is undersized for the load. The most direct and code-compliant
solution is to upsize the pipe to a size that can deliver the required CFH, which in this
case would be 1.25-inch. Increasing pressure may not be permissible and doesn't
address the root cause. Parallel pipes are complex and rarely used in standard practice.
11. The total connected load for a building is 450,000 BTU/hr. What is the
approximate minimum capacity the gas meter and service line must have?
a) 450 CFH
b) 450 BTU/hr
c) 450 CCF
d) 450 therms
Answer: A
Explanation: For natural gas, a common rough approximation is 1 CFH ≈ 1000 BTU/hr.
Therefore, 450,000 BTU/hr / 1000 BTU/hr per CFH = 450 CFH. The meter and service
must be sized to handle the total connected load, not just the demand load.
12. When sizing a manifold system for a building with multiple apartments, the
diversity factor is applied to:
a) The pipe size for each individual apartment.
b) The pressure drop across the regulator.
c) The total load used to size the main trunk line.
d) The length of the service line from the street.
Answer: C
Explanation: A diversity factor acknowledges that not all appliances in all units will be
operating at peak capacity simultaneously. This allows the main trunk line and meter to
be sized for a "demand load" that is less than the sum of all individual "connected
loads," leading to a more economical design.
13. What is the minimum required coverage for a steel gas pipe buried
underground?
a) 6 inches
b) 12 inches
c) 18 inches
d) 24 inches
Answer: B
Explanation: The IFGC typically requires a minimum cover of 12 inches for steel gas
piping to protect it from physical damage and, in some cases, frost lines. Local codes
may require deeper burial, so they must always be checked.
