Exam Cheat Sheet · Quick Reference

Maryland Master Natural Gas Fitter

Maryland  ·  PSI Services Contractor

Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.
Total questions
40
Passing score
70%
Exam time
90 min
Administered by
PSI Services Contractor
Format
Reference materials allowed

Maryland State Portion 40 questions

General Piping 15 Q · 38%
Allowable pressure drop and maximum operating pressure limitsApproved piping materials and tubing standards (steel, copper, CSST, polyethylene)Pipe joints, fittings, and thread specifications for metallic and plastic pipingPiping system installation requirements (prohibited locations, underground burial depth, protection from physical damage)Pressure testing, inspection, and purging proceduresShutoff valves and flow controls (placement, access, and regulator requirements)Pipe length calculations including fitting allowances and offset geometry
Pipe Sizing/Math 10 Q · 25%
Gas pipe sizing methods (longest length, branch length, hybrid pressure)Pressure drop calculations and allowable loss in gas piping systemsConverting BTU/h appliance demand to cubic feet per hourEquivalent length of pipe fittings and valves for gas systemsFitting allowances for threaded, copper, and welded pipe (center-to-center vs. end-to-end)Offset calculations using trigonometric constants (45°, 60°, 22.5° angles)Pipe volume and capacity calculations (gallons per linear foot, cylinder volume)Grade, drop, and elevation calculations for sloped piping
Chimney and Flues 5 Q · 12%
Types of venting systems and appliance categories (Type B, BW, L, single-wall metal pipe, direct-vent, Category I–IV)Vent and chimney termination location requirementsSizing of Category I appliance venting systems using code tablesVent connector materials, clearances, slope, and installation requirementsMasonry chimney construction, lining, inspection, and cleanout requirementsDraft hoods, draft controls, and automatically operated vent dampersCommon venting and multistory venting system designExit terminal clearances for mechanical draft and direct-vent systems
Combustion 5 Q · 12%
Combustion air requirements for indoor spaces (standard method: 50 cu ft per 1,000 Btu/h)Outdoor combustion air opening sizing and placement methods (one- and two-opening methods)Combination indoor and outdoor combustion air systemsMechanical combustion air supply systems and appliance interlock requirementsLouvers, grilles, and screens: free area calculations and motorized louver interlockingCombustion air duct construction, materials, and installation requirementsDefinitions of combustion, combustion air, combustion products, and related termsFlammable limits and properties of natural gas and propane relevant to combustion safety
Appliances 5 Q · 12%
Listing, labeling, and testing standards for specific appliance typesInstallation clearances to combustible materials for heaters and furnacesUnvented room heater restrictions, input ratings, and oxygen-depletion safety shutoff requirementsClothes dryer exhaust duct materials, length limits, termination requirements, and makeup airCooking appliance installation requirements, clearances, and prohibited locationsSafety inspection procedures for existing appliance installations including CO thresholds by appliance typeFlame safeguard devices and ignition systems for decorative and fireplace appliancesWater heater installation, relief valve requirements, and dual-use space heating applications

Key Distinctions

Pipe (code definition)vsTubing (code definition)

Pipe is a rigid conduit of iron, steel, copper, copper-alloy, or plastic, while tubing is a semirigid conduit of copper, copper-alloy, aluminum, plastic, or steel — notably aluminum is only in the tubing definition.

2018 IFGC, Page 15, Section 202 (Piping definition)
Flared JointvsFlanged Joint

A flared joint uses a conical spread on tube end compressed by a flare nut against a mating flare, while a flanged joint is made by bolting together a pair of flanged ends.

2018 IFGC, Page 15, Section 202 (Joint, Flared definition)
Flared JointvsPlastic Heat Fusion Joint

A flared joint is a metal-to-metal compression connection using a conical tube end and flare nut, while a plastic heat fusion joint is made by heating thermoplastic parts until they fuse when pressed together.

2018 IFGC, Page 15, Section 202 (Joint, Flared definition)
Longest Length Method (pipe sizing)vsIndividual Section Load Method

The longest length method sizes each pipe section using the single longest run from point of delivery to the most remote outlet plus that section's load, rather than calculating equivalent lengths for each branch independently.

2018 IFGC, Page 32, Section 402.4.1
Appliance Shutoff Valve in Same RoomvsAppliance Shutoff Valve at Manifold

A same-room shutoff valve must be within 6 feet of the appliance and upstream of the union/connector, while a manifold shutoff valve may be up to 50 feet from the appliance but must be readily accessible and permanently identified.

2018 IFGC, Page 77, Section 409.5.1
CSST Bonding RequirementsvsNon-CSST Gas Piping Bonding

CSST has more stringent bonding requirements, whereas non-CSST gas piping is considered bonded simply by being connected to an appliance that is connected to the equipment grounding conductor of its supply circuit.

2018 IFGC, Page 28, Section 310.1
Standard Weight Steel PipevsExtra-Heavy / Double Extra-Heavy Steel Pipe

All three weights share the same outside diameter for a given nominal size (allowing the same threading dies), but differ in wall thickness and inside diameter.

Mathematics for Plumbers and Pipefitters, Page 35 (Standard Weight Pipe)
No-Hub Cast Iron JointvsHubbed Cast Iron Joint

No-hub joints use a No-Hub gasket enclosed by a stainless steel shield with a stainless steel retaining clamp, while hubbed joints use either lead and oakum or compression gaskets.

Mathematics for Plumbers and Pipefitters, Page 105 (Unit 27, Cast Iron Pipe)
Copper Tubing Type KvsCopper Tubing Types L, M, and DWV

All four types share the same outside diameter for a given nominal size, but Type K has the thickest wall (smallest inside diameter) and is the primary recommendation for underground service, while L, M, and DWV have progressively thinner walls.

Mathematics for Plumbers and Pipefitters, Page 42 (Copper Tubing)
Maximum Operating Pressure — Natural Gas (IFGC scope)vsMaximum Operating Pressure — LP-Gas (IFGC scope)

The IFGC covers natural gas systems up to 125 psig, while LP-gas systems are covered only up to 20 psig (except as provided in Section 402.7).

2018 IFGC, Page 1, Section 101.2.2
Pressure Regulator with Vent-Limiting DevicevsStandard Vented Pressure Regulator

A regulator equipped with and labeled for an approved vent-limiting device does not require a vent piped to the outdoors, while a standard vented regulator must be vented directly outdoors.

2018 IFGC, Page 78, Section 410.3
Laboratory Gas Shutoff Valve RequirementvsMulti-Tenant Building Shutoff Valve Requirement

A laboratory with two or more outlets requires one dedicated shutoff valve for all outlets, located adjacent to the egress door with 'Gas Shutoff' signage, while a multi-tenant building requires individual shutoff valves accessible to each tenant.

2018 IFGC, Page 77, Section 409.6

Key Terms

Maximum Inside-Building Operating Pressure (non-welded/brazed/flanged joints) 2018 IFGC, Page 32, Section 402.7
Per IFGC Section 402.7, gas piping inside buildings with joints that are not welded, brazed, or flanged shall not exceed 5 psig operating pressure.
Overpressure Protection Device Limit (14 in. w.c. appliances) 2018 IFGC, Page 83, Section 416.2.1
Per IFGC Section 416.2.1, where appliances are rated at 14 in. w.c. or less and overpressure protection is required, each device must limit gas pressure to 2 psi or less upon line-regulator failure.
Prohibition on Cast-Iron Pipe in Fuel Gas Systems 2018 IFGC, Page 69, Section 403.4.1
Per IFGC Section 403.4.1, cast-iron pipe is explicitly prohibited from use in fuel gas piping systems.
Polyethylene Plastic Pipe Standard for Fuel Gas 2018 IFGC, Page 69, Section 403.6
Per IFGC Section 403.6, polyethylene plastic pipe used for fuel gas must conform to ASTM D2513 and be marked 'Gas' and 'ASTM D2513.'
Brazing Material Requirements for Nonferrous Gas Pipe 2018 IFGC, Page 70, Section 403.10.1
Per IFGC Section 403.10.1, brazing materials for nonferrous gas pipe must have a melting point exceeding 1,000°F and brazing alloys must not contain more than 0.05% phosphorus.
Underground Gas Piping — Foundation Wall Penetration Rule 2018 IFGC, Page 71, Section 404.6
Per IFGC Section 404.6, gas piping shall not penetrate building foundation walls below grade; it must enter and exit above grade with the annular space sealed.
Minimum Burial Depth for Underground Gas Piping 2018 IFGC, Page 72, Section 404.12
Per IFGC Section 404.12, underground gas piping systems must be installed a minimum of 12 inches below grade (individual outdoor appliance lines may be at 8 inches).
Pressure Test Duration (system < 10 ft³ or single-family dwelling) 2018 IFGC, Page 74, Section 406.4.2
Per IFGC Section 406.4.2, the minimum pressure test duration for systems with volume less than 10 cubic feet or in a single-family dwelling is 10 minutes.
Purging Stop Point (systems > 2 psig design pressure) 2018 IFGC, Page 75, Section 406.7.1.3
Per IFGC Section 406.7.1.3, during outdoor discharge purging of systems with design pressure greater than 2 psig, introduction of fuel gas must stop when 90% fuel gas by volume is detected in the pipe.
Shutoff Valve Prohibited Locations 2018 IFGC, Page 77, Section 409.1.2
Per IFGC Section 409.1.2, shutoff valves are prohibited in concealed locations and furnace plenums.
Gas Piping as Grounding Electrode — Prohibition 2018 IFGC, Page 28, Section 309.1
Per IFGC Section 309.1, gas piping shall not be used as a grounding electrode.
CSST Additional Fitting Length Formula 2018 IFGC, Page 47, Table 402.4(15) Note 1
Per IFGC Table 402.4(15) Note 1, for CSST runs with fittings beyond the four 90-degree bends and two end fittings already included in the table, add equivalent length L = 1.3n feet, where n is the number of additional fittings or bends.
Piping System (code definition) 2018 IFGC, Page 15, Section 202 (Piping System definition)
Per IFGC Section 202, the piping system extends from the outlet of the point of delivery to the outlets of the appliance shutoff valves, including all fuel piping, valves, and fittings in between.
Point of Delivery (natural gas) 2018 IFGC, Pages 15-16, Section 202 (Point of Delivery definition)
Per IFGC Section 202, the point of delivery for natural gas is the outlet of the service meter assembly, or the outlet of the service regulator or service shutoff valve where no meter is provided.
Pressure Drop (code definition) 2018 IFGC, Page 16, Section 202 (Pressure Drop definition)
Per IFGC Section 202, pressure drop is the loss in pressure due to friction or obstruction in pipes, valves, fittings, regulators, and burners.
Mechanical Joint (code definition) 2018 IFGC, Page 15, Section 202 (Joint, Mechanical definition)
Per IFGC Section 202, a mechanical joint is a gas-tight joint obtained by positive-holding mechanical construction, including press-connect, flanged, threaded, flared, and compression joints.

Formulas to Know

CSST Additional Equivalent Length for Extra Fittings/BendsL = 1.3 × n (L = additional feet of tubing; n = number of fittings or bends beyond the 4 standard 90° bends and 2 end fittings already in the table)
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