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Maryland Master Natural Gas Fitter — Practice Exam

What This Practice Exam Covers

The Maryland Master Natural Gas Fitter licensing exam consists of 40 questions answered in 90 minutes, with a passing score of 70% (28 correct). The exam draws from five topic areas covering general piping, pipe sizing math, chimneys and flues, combustion air, and appliances — all grounded in the 2018 International Fuel Gas Code (IFGC) and supporting reference materials.

This practice exam comes in two versions:

• Free practice exam: 10 questions per attempt, drawn from a limited pool. You can retake it as many times as you like — it's a solid way to get a feel for question style and phrasing before committing to full prep.
• Full practice exam (paid): Mirrors the real exam with exactly 40 questions and a 90-minute time limit, drawn from a pool of 194+ questions. Every attempt pulls a different set, so retakes test fresh material rather than repeated memorization. Questions are built from the same topic distribution as the official exam.

Start with the free version to locate your weak spots, then use the full exam for timed, realistic practice.

What You'll Be Tested On

General Piping — 15 Questions (Largest Topic)

This is the most heavily weighted section and deserves the most preparation time. You must know allowable pressure drop and maximum operating pressure limits — including the 2 psi overpressure protection threshold under IFGC Section 416.2.1. Expect questions on approved piping materials: steel, copper, CSST, and polyethylene each have specific standards and permitted applications.

Joints and fittings require detail-level knowledge: flanged, flared, mechanical, and plastic heat-fusion joints are each defined in IFGC Section 202 and carry distinct application rules. Thread specifications for metallic and plastic pipe are tested separately.

Installation requirements include prohibited locations for piping, underground burial depth, and protection from physical damage — know these as hard minimums, not guidelines. Pressure testing is its own subtopic: inspection procedures, test medium, acceptable pressure loss, and hold time. Purging procedures follow testing and are tested independently.

Finally, shutoff valves require you to know placement rules, accessibility requirements, and regulator sizing — covered under IFGC Sections 409 and 410.

Pipe Sizing and Math — 10 Questions

The exam tests three sizing methods: longest length, branch length, and hybrid pressure. You need to know when each applies and how to execute the steps, not just identify the method name.

Pressure drop calculations require you to convert appliance BTU/h ratings to cubic feet per hour (divide by the heating value of the gas), then apply sizing tables or formulas for the allowable pressure loss in a given system.

Equivalent length is heavily tested. You must add fitting equivalent lengths — from IFGC Appendix A, Table A.2.2 — to actual pipe run lengths before sizing. A 1-inch screwed 90° elbow, for example, adds 2.62 feet of equivalent pipe. Threaded, copper, and welded fittings each have separate allowance tables drawn from Mathematics for Plumbers and Pipefitters.

Offset calculations using trigonometric constants appear on this exam. You must be comfortable working with the constants for 45°, 60°, and 22.5° offsets — multiplying the known dimension by the correct constant to find pipe length or offset travel. These are standard, testable formulas from Mathematics for Plumbers and Pipefitters, Chapters 5 and 25.

Chimney and Flues — 5 Questions

Questions focus on appliance venting categories (I–IV) and the correct vent type for each: Type B, BW, L, single-wall metal pipe, and direct-vent systems are all fair game. Know which appliances go with which vent category — confusing Category I with Category IV is a common error.

Termination locations are tested with specific clearance distances — how far from windows, doors, grade, and adjacent walls. Vent connector slope, clearance to combustibles, and connector materials are detailed requirements under IFGC Section 503.

Single-wall metal pipe has a specific outdoor use restriction: per IFGC Section 503.7.2, it cannot be used outdoors where the 99-percent winter design temperature falls below 32°F.

Masonry chimney questions cover lining requirements, cleanout access, and inspection standards. Draft hoods and automatically operated vent dampers are also tested — know their function and installation rules.

Combustion Air — 5 Questions

The fundamental rule is 50 cubic feet of space per 1,000 Btu/h of total appliance input for the standard (indoor air) method. Questions often present a total input load and ask for the minimum room volume or combined space volume required.

The one-opening and two-opening outdoor air methods each have distinct sizing requirements — opening area, placement height, and duct dimensions differ between them. Know both and be able to apply them numerically.

Louvers, grilles, and screens reduce free area — you must apply the correct reduction factor (typically 25% for wood louvers, 75% for metal) when calculating effective opening size. Motorized louver interlocks with appliance operation are also tested. Mechanical combustion air supply systems require an appliance interlock so the appliance cannot operate if the air supply fails.

Appliances — 5 Questions

This section covers listing and labeling standards, clearances to combustibles for heaters and furnaces, and the rules for unvented room heaters — including input rating caps and mandatory oxygen-depletion safety shutoff (ODS) requirements.

Clothes dryer exhaust is a standalone subtopic: duct material (rigid metal), maximum length limits, termination requirements, and makeup air provisions are all tested. Cooking appliance clearances and prohibited installation locations round out this section. Expect at least one question on CO thresholds used during safety inspections of existing installations.

Worked Sample Questions

Question 1 — General Piping: Overpressure Protection

You are designing a natural gas piping system for a new commercial building. The gas supplier delivers gas at a pressure greater than 2 psi, and the appliances are designed for 14 inches w.c. or less. Upon failure of the line pressure regulator, each overpressure protection device must be adjusted to limit gas pressure to each connected appliance to what maximum value?

A. 1 psi
B. 5 psi
C. 14 inches w.c.
D. 2 psi

Correct Answer: D — 2 psi

The appliances are rated for 14 inches w.c., which is less than 2 psi. Option C looks tempting because it matches the appliance rating — but the question asks what the overpressure protection device must limit pressure to, not what the appliance normally operates at. Per 2018 IFGC, Page 83, Section 416.2.1, when serving appliances rated at 14 inches w.c. or less, each overpressure protection device must be set to limit pressure to 2 psi or less upon regulator failure. The device provides a safety ceiling, not an operating setpoint.

Question 2 — Pipe Sizing/Math: Equivalent Length of Fittings

When using the equivalent length table for gas piping components, a 1-inch screwed 90° elbow has an equivalent length closest to which value?

A. 5.24 feet
B. 1.22 feet
C. 2.62 feet
D. 5.82 feet

Correct Answer: C — 2.62 feet

This is a direct table lookup from IFGC 2018, Appendix A, Table A.2.2. For a 1-inch nominal screwed 90° elbow, the equivalent length is 2.62 feet. The underlying calculation uses a k factor of 0.90 and an L/d ratio of 30, applied to the actual inside diameter of a 1-inch pipe (1.049 inches). On the exam, you won't derive this from scratch — you read the table — but understanding the relationship between pipe diameter and equivalent length helps when the question changes the pipe size.

Question 3 — Chimney and Flues: Single-Wall Metal Pipe Outdoor Use

Uninsulated single-wall metal pipe is prohibited from being used outdoors for venting gas appliances in regions where the 99-percent winter design temperature is below what value?

A. 32°F
B. 40°F
C. 0°F
D. 20°F

Correct Answer: A — 32°F

Per IFGC, Section 503.7.2, uninsulated single-wall metal pipe cannot be used outdoors in regions where the 99-percent winter design temperature falls below 32°F (0°C). Option C (0°F) is a common wrong answer because candidates confuse the Fahrenheit threshold with the Celsius equivalent — the code gives the limit as 32°F, which is 0°C. Maryland's climate makes this restriction relevant, and the exam tests it precisely.

How to Read Your Score

The passing score is 70%, which means 28 correct out of 40. On the practice exam, treat your first attempt as a diagnostic — it tells you where your knowledge has gaps, not whether you will pass the real exam.

A score in the 80–100% range suggests solid readiness, particularly if you're scoring consistently across all five topics. A score in the 70–79% range means you're near the threshold but don't have margin for a bad day — targeted review of your weakest topics is still necessary.

A score below 70% on practice is useful information, not a verdict. Look at which topics dragged your score down. General Piping (15 questions) and Pipe Sizing/Math (10 questions) together account for 62.5% of the exam — weak performance in either one has an outsized effect on your total score. Use the topic breakdown to prioritize, not to panic.

Retake the full practice exam after focused study. Because it draws from a 194+ question pool, each attempt surfaces new questions and gives you a more accurate picture of actual readiness than repeating the same 40 questions would.

Where Candidates Lose Points

Unit confusion in pipe sizing is the single most common error. Candidates who forget to convert BTU/h to cubic feet per hour before entering a sizing table will pull the wrong pipe size every time — and lose multiple related questions as a result.

Wrong fitting allowance table costs points in the math section. Threaded, socket-weld, and butt-weld fittings each use different allowance methods from Mathematics for Plumbers and Pipefitters. Mixing them up produces plausible-looking wrong answers.

Venting category misidentification is the dominant error in Chimney and Flues. Candidates who cannot reliably distinguish Category I from Category IV — or who select Type B vent for an appliance that requires Type L — will consistently miss those questions.

Combustion air method confusion trips up candidates who apply the one-opening outdoor method rules to a two-opening layout, or who forget to derate louver free area before calculating opening size.

Time management on General Piping is a structural risk. With 15 questions in one topic, it's easy to spend too long on pressure testing or shutoff valve questions and arrive at the math section without enough time for the multi-step offset and sizing problems that require full attention.

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