Exam Cheat Sheet · Quick Reference
Kansas City, MO Master Gas Pipe Fitter Exam (ICC G33, 2018 IFGC)
Missouri · Pearson Vue
Missouri State Portion 75 questions
Key Distinctions
Per IFGC Section 202, '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 (aluminum appears only under tubing).
IFGC 2018 Section 202 (Piping definition)A pressure test verifies the gas-tight integrity of gas piping following its installation or modification, while a leak check is performed to verify that the system does not leak (during/after being placed in service).
IFGC 2018 Section 202, DefinitionsFlue gases are products of combustion plus excess air in appliance flues or heat exchangers, whereas combustion products are the constituents from burning fuel with oxygen (including inert gases) but excluding excess air.
IFGC 2018 Chapter 2 DefinitionsCombustion air is the air necessary for complete combustion of a fuel, including theoretical air and excess air; dilution air is air introduced into a draft hood and mixed with the flue gases.
IFGC 2018 Chapter 2 DefinitionsDetached one- and two-family dwellings and townhouses not more than three stories high with separate means of egress, and their accessory structures, go to the IRC; a four-story townhouse exceeds that limit and remains under the IFGC.
IFGC 2018 Section 101.2, ExceptionNon-arc-resistant CSST must be electrically continuous and bonded to the electrical service grounding electrode system with a bonding jumper not smaller than 6 AWG copper (or equivalent), while arc-resistant-jacketed CSST is considered bonded where it connects to an appliance connected to the appliance grounding conductor of the circuit supplying that appliance.
IFGC 2018 Section 310.2.2Listed draft-hood appliances require a ventilated metal thimble not less than 4 inches larger in diameter than the pipe (reduced to not less than 2 inches larger where there is a run of not less than 6 feet of metal pipe in the open between draft hood outlet and thimble), while unlisted draft-hood appliances require not less than 6 inches larger in diameter.
IFGC 2018 Section 503.7.7Horizontal ducts require each opening to have not less than 1 square inch of free area per 2,000 Btu/h of total input, while direct openings or vertical ducts require not less than 1 square inch per 4,000 Btu/h; the one-permanent-opening method of 304.6.2 uses 1 square inch per 3,000 Btu/h.
IFGC 2018 Section 304.6.1Per IFGC 304.10, where design and free area are not known, wood louvers are assumed to have 25-percent free area and metal louvers/grilles 75-percent free area.
IFGC 2018 Chapter 3 — Section 304.10Same-story spaces are connected by two permanent openings, EACH having 1 square inch per 1,000 Btu/h of total input but in no case less than 100 square inches (openings commencing within 12 inches of top and bottom, minimum dimension 3 inches); different-story spaces require permanent openings in doors or floors with a TOTAL minimum free area of 2 square inches per 1,000 Btu/h of total input.
IFGC 2018 Section 304.5.3.1Piping systems with a design operating gas pressure greater than 2 psig are required to be purged outdoors; indoor purging (e.g., through an appliance burner) is allowed only for systems at 2 psig or less that also do not meet the size and length criteria of Table 406.7.1.1.
IFGC 2018 Section 406.7.1A manifold valve is permitted where it is within 50 feet of the appliance served, readily accessible and permanently identified, with the piping from the manifold to within 6 feet of the appliance designed, sized and installed per Sections 401 through 408; shutoff valves are prohibited in concealed locations and furnace plenums.
IFGC 2018 Section 409.5.3Key Terms
Formulas to Know
Required volume (ft³) = 50 ft³ × (total appliance input Btu/h ÷ 1,000), summed for all appliances in the space. Examples: (120,000 + 60,000) ÷ 1,000 × 50 = 9,000 ft³; (150,000 + 50,000) ÷ 1,000 × 50 = 10,000 ft³.Fan-assisted: (15 ÷ ACH) × (Ifan ÷ 1,000); other than fan-assisted: (21 ÷ ACH) × (Iother ÷ 1,000); add the two. ACH greater than 0.60 shall not be used in the equations. Example with 0.75 ACH measured (use 0.60): (15÷0.60)×90 = 2,250 ft³ plus (21÷0.60)×30 = 1,050 ft³ = 3,300 ft³.Two permanent openings through horizontal ducts: each opening ≥ 1 in² per 2,000 Btu/h of total input (e.g., 140,000 ÷ 2,000 = 70 in²; 160,000 ÷ 2,000 = 80 in²). Two permanent openings communicating directly with outdoors or through vertical ducts: each opening ≥ 1 in² per 4,000 Btu/h (e.g., 120,000 ÷ 4,000 = 30 in²). One-permanent-opening method: 1 in² per 3,000 Btu/h.Ratio of interior spaces = available volume ÷ required volume; reduction factor = 1 − ratio; required outdoor opening = full outdoor opening size (per 304.6) × reduction factor. Examples: 0.60 ratio → 0.40 factor (openings at 40% of full size); 3,000 ÷ 6,000 = 0.50 → 0.50 factor applied to 120,000 ÷ 3,000 = 40 in² one-opening size = 20 in² (and not less than the sum of vent connector areas, minimum dimension 3 inches).Gross area = required free area ÷ assumed free-area fraction, using 25% (0.25) for wood louvers and 75% (0.75) for metal louvers/grilles. Examples: 90 ÷ 0.25 = 360 in² (wood); 50 ÷ 0.25 = 200 in² (wood over a 100,000 Btu/h horizontal-duct opening).Minimum outdoor air = 0.35 cfm per 1,000 Btu/h of total input. Example: 1,200,000 Btu/h → 1,200 × 0.35 = 420 cfm (appliances must be interlocked with the air supply system per 304.9.2).Test pressure = not less than 1-1/2 × proposed maximum working pressure, but not less than 3 psig irrespective of design pressure. Example: 1.5 × 1 psig = 1.5 psig, so the 3 psig floor governs.Not less than 1/2 hour for each 500 ft³ of pipe volume or fraction thereof, need not exceed 24 hours (example: 1,100 ft³ = 3 increments × 1/2 hour = 1-1/2 hours). For a system of less than 10 ft³ volume or a system in a single-family dwelling, duration shall be not less than 10 minutes.Demand (cfh) = Btu/h ÷ 1,000, summed for all outlets downstream of the section; each section is then sized from Table 402.4(2) using the system's longest length row (not the branch's own length) and selecting a size whose listed capacity meets or exceeds the demand. Worked examples: (50,000+40,000+100,000) ÷ 1,000 = 190 cfh total; section B = 140 cfh → 3/4 in. (151 cfh at 50 ft) vs 1/2 in. (72 cfh); section A 3/4 in. at 60 ft = 137 cfh vs 135 cfh demand (margin 2 cfh); branch of 40 cfh at the 70-ft row = 1/2 in. (60 cfh).Single-appliance venting configurations WITH LATERAL LENGTHS already include two 90-degree elbows; reduce listed maximum capacity 10 percent for each additional elbow greater than 45 up to and including 90 degrees (three 90s = one 10-percent reduction). Multiple-appliance connectors: horizontal length limited to 1-1/2 ft per inch of diameter (6 in. × 1.5 = 9 ft); longer runs reduce maximum connector capacity 10 percent per additional multiple (14 ft → 0.90 × max; over 18 ft up to 27 ft → 20 percent). Listed corrugated metallic liners in masonry chimneys: maximum capacity reduced 20 percent (0.80 ×), minimum capacity used as shown. Multistory common vent segment containing the single permitted 45-degree offset: common vent capacity reduced 20 percent. Common vent area in a masonry chimney shall be not greater than seven times the smallest listed appliance categorized vent area, flue collar area or draft hood outlet area.