Exam Cheat Sheet · Quick Reference
Denver Master Gas Pipe Fitter Exam (ICC F33, 2015 IFGC)
Colorado · Pearson Vue
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
75
Passing score
70%
Exam time
180 min
Administered by
Pearson Vue
Format
Reference materials allowed
Colorado State Portion 75 questions
General Requirements
29 Q · 39%
Code scope and applicability (fuel gas piping systems, appliances, and excluded installations)Permits, inspections, and approval processKey definitions (point of delivery, piping system, appliance, regulator, CSST, LP-gas, etc.)Piping identification, labeling, and manufacturer marking requirementsAppliance listing, labeling, and installation requirementsStructural safety and protection of building members during piping installationProhibited locations for appliances and pipingElectrical bonding and grounding requirements for gas piping systemsGeneral RegulationsScope and AdministrationGas Piping InstallationsDefinitions
Appliances and Equipment
10 Q · 13%
Appliance listing, labeling, and approval requirementsProhibited and restricted appliance locationsClearances to combustible construction and clearance reduction methodsAccess and service space requirements for appliancesSpecific appliance installation requirements (furnaces, boilers, water heaters, unit heaters, unvented room heaters, clothes dryers, cooking appliances)Elevation of ignition sources in garages and hazardous locationsCondensate disposal for fuel-burning and cooling appliancesGeneral RegulationsSpecific Appliances
Fuel Supply Systems
13 Q · 17%
Gas pipe sizing methods (longest length, branch length, and hybrid pressure methods)Pipe sizing table selection based on gas type, inlet pressure, and allowable pressure dropAltitude adjustment for gas demand above 2,000 feet elevationApproved piping and tubing materials (steel, copper, CSST, polyethylene, aluminum alloy)Piping installation requirements (burial depth, prohibited locations, underground penetrations, protection from physical damage)Pressure testing and purging procedures for gas piping systemsShutoff valve requirements (location, appliance shutoff, meter valve, multiple-meter systems)Pressure regulators and overpressure protection devicesGas Piping Installations
Combustion Air
9 Q · 12%
Indoor combustion air volume requirements (standard method and known air-infiltration-rate method)Outdoor combustion air openings: two-permanent-openings method sizing and placementOutdoor combustion air openings: one-permanent-opening method sizing and placementCombination indoor and outdoor combustion air sizing calculationsMechanical combustion air supply systems and appliance interlock requirementsLouvers, grilles, and screens: free area calculations and motorized louver interlock requirementsCombustion air duct construction, installation, and termination requirementsProtection from corrosive or flammable fumes affecting combustion air supply
Chimneys and Vents
10 Q · 13%
Appliance venting categories and vent type selection (Types B, BW, L, single-wall metal, special gas vent)Venting system sizing using Section 504 tables for Category I appliances (single and multiple appliances)Vent and chimney termination requirements (height, location, clearances from openings and inlets)Vent connector materials, construction, clearances, slope, and length limitationsMasonry chimney requirements (lining, cleanouts, inspection, and connection rules)Draft hoods and draft controls (installation, location, clearance, and prohibited dampers)Appliances not required to be vented and aggregate input rating limits for unvented appliancesMechanical draft systems, positive-pressure venting, and direct-vent appliance installation requirementsChimneys and Vents
Special Requirements
4 Q · 6%
Installation requirements for specific appliance types (fireplaces, furnaces, heaters, dryers, boilers)Clearances to combustible materials for specific appliancesFlame safeguard and safety shutoff device requirementsProhibited locations and occupancy restrictions for specific appliancesClothes dryer exhaust duct sizing, materials, and length limitationsUnvented room heater input rating limits and oxygen-depletion safety systemsGaseous hydrogen system piping design, materials, and identification requirementsPressure testing and purging procedures for gaseous hydrogen piping systemsSpecific Appliances
Key Distinctions
Longest length method (IFGC 402.4.1)vsBranch length method (IFGC 402.4.2)
The longest length method sizes every section of the system from the single table row for the distance to the most remote outlet, while the branch length method sizes each branch from its own meter-to-outlet length (mains on the longest run still use the longest-run row).
IFGC Section 402.4.1, Longest Length Method; Table 402.4(2), Schedule 40 Metallic Pipe (natural gas, 0.5 in. w.c. drop)Appliance in a private garage (305.5)vsAppliance in a public garage (305.4)
Private-garage appliances require a minimum 6 feet of clearance above the floor (exception where protected from vehicle impact and installed per 305.3), while public-garage appliances must be not less than 8 feet above the floor, and not less than 1 foot higher than the tallest vehicle garage door opening where vehicles can pass beneath.
IFGC 2015 Section 305.5Appliance set on a slab at grade (305.7)vsAppliance suspended above grade (305.7)
A level concrete slab or other approved material must extend not less than 3 inches above adjoining grade, whereas a suspended appliance on an approved support must be not less than 6 inches above adjoining grade.
IFGC 2015 Section 305.7Outdoor combustion air openings direct to outdoors or via vertical ducts (304.6.1)vsOutdoor combustion air openings via horizontal ducts (304.6.1)
Direct or vertical-duct openings require not less than 1 square inch per 4,000 Btu/h of total input, while horizontal ducts require 1 square inch per 2,000 Btu/h.
IFGC 2015 Section 304.6.1Unvented room heater in a bedroom (303.3, Item 4)vsUnvented room heater in a bathroom (303.3, Item 3)
A single wall-mounted unvented room heater in a bedroom is limited to an input rating not greater than 10,000 Btu/h, while the bathroom limit in Item 3 is 6,000 Btu/h (heater must have oxygen depletion safety shutoff and the room must meet the Section 304.5 volume criteria).
IFGC 2015 Section 303.3Low-pressure steam heating boiler (Section 202)vsHot water heating / hot water supply boiler (Section 202)
A steam heating boiler generates steam and operates at a steam pressure not exceeding 15 psig, whereas the 160 psig figure is the water pressure limit stated for hot water heating and hot water supply boilers.
IFGC 2015 Section 202 (definition of 'Boiler, Low-Pressure')Unit heater — high-static pressure type (Section 202)vsUnit heater — low-static pressure type (Section 202)
The high-static type circulates air against 0.2 inch water column or greater static pressure and has provisions for attaching an outlet air duct; the low-static type is intended for installation in the space to be heated without ducts.
IFGC 2015 Section 202 (definition of 'Unit Heater')Thimble 4 inches larger in diameter (503.7.7, Item 1)vsThimble 2 inches larger in diameter (503.7.7, Item 1 allowance)
A single-wall metal pipe vent from a listed draft-hood appliance passing through a combustible exterior wall normally needs a ventilated thimble not less than 4 inches larger in diameter, but not less than 2 inches larger is permitted where there is a run of not less than 6 feet of metal pipe in the open between the draft hood outlet and the thimble; the 6-inch and 12-inch figures apply to unlisted draft-hood appliances and to residential/low-heat appliances respectively.
IFGC 2015 Section 503.7.7Field bend in polyethylene plastic pipe (405.3, Item 3)vsBend in metallic pipe (405.2, Item 5)
Plastic pipe bends require the radius of the inner curve to be not less than 25 times the inside diameter of the pipe, while metallic pipe bends have a minimum inside radius of 6 times the outside diameter.
IFGC 2015 Section 405.3Furnace output rating capacity (618.2)vsFurnace input rating
Return air and outdoor air duct/opening area is sized on the furnace OUTPUT rating capacity at 2 square inches per 1,000 Btu/h; using the input rating is a common error (e.g., 120,000 Btu/h output = 240 sq in, not the 300 sq in from a 150,000 Btu/h input).
IFGC 2015 Section 618.2Medium-heat appliance (Section 202, 'Appliance Type')vsLow-heat (residential) appliance (Section 202, 'Appliance Type')
A medium-heat appliance has flue-entrance combustion products greater than 1,000°F but not greater than 2,000°F under normal operation; at or below 1,000°F the appliance is a low-heat (residential) appliance.
IFGC 2015 Section 202 (definition of 'Appliance Type')Gas vent termination by Figure 503.6.4 (503.6.4, Item 1)vsGas vent termination by the 2-foot rule (503.6.4, Item 2)
Vents 12 inches or less in size located not less than 8 feet from a vertical wall or similar obstruction may terminate per Figure 503.6.4, while vents over 12 inches in size or located less than 8 feet from such an obstruction must terminate 2 feet above the roof penetration and 2 feet above any portion of a building within 10 feet horizontally.
IFGC 2015 Section 503.6.4Board of appeals seat filled by a registered design professional (109.2.1)vsBoard of appeals seat filled by a fuel gas contractor (109.2.1)
The seat may be filled by a registered design professional with fuel gas and plumbing engineering experience, or alternatively by a fuel gas contractor with not less than 10 years' experience, 5 of which were in responsible charge of work.
IFGC 2015 Section 109.2.1Key Terms
Scope exclusions — special atmosphere generator (101.2.4) IFGC 2015 Section 101.2.4
Section 101.2.4 lists systems outside the code's scope, and Item 3 excludes raw material (feedstock) applications 'except for piping to special atmosphere generators,' so piping to a special atmosphere generator remains regulated, while atomic energy plant fuel gas piping, railroad switch heating LP-gas systems, and temporary LP-gas piping not becoming part of the permanent system are outside the scope.
Board of appeals vote (109.6) IFGC 2015 Sections 109.5 and 109.6
The board modifies or reverses a decision of the code official by a concurring vote of three members; Section 109.5 lets an appellant request a postponement when five members are not present, but if the appellant proceeds, three concurring votes still decide the appeal.
Mechanical gauge for pressure testing (406.4) IFGC 2015 Section 406.4
A mechanical gauge used to measure test pressure must have a range whose highest end of scale is not greater than five times the test pressure, and the source of pressure must be isolated before the test.
Double block and bleed valve system (406.1.4) IFGC 2015 Section 406.1.4
The only condition under which a valve in a line may serve as a bulkhead between fuel gas in one section and the test medium in an adjacent section during section testing.
Appliance shutoff valve at a manifold (409.5.3) IFGC 2015 Section 409.5.3
An appliance shutoff valve may be grouped at a manifold rather than within 6 feet of the appliance where it is located within 50 feet of the appliance served, is readily accessible and permanently identified, with piping from the manifold to within 6 feet of the appliance designed, sized and installed per Sections 401 through 408.
Conduit for piping in a solid floor (404.8) IFGC 2015 Section 404.8
As an alternative to channels, piping in a solid floor may be installed in a conduit of Schedule 40 steel, wrought iron, PVC or ABS pipe, installed per Section 404.8.1 or 404.8.2.
Conduit terminating outdoors (404.8.1) IFGC 2015 Sections 404.8 and 404.8.1
Such conduit must extend not less than 4 inches outside the building, be vented above grade to the outdoors, be installed to prevent entrance of water and insects, and extend not less than 2 inches beyond the point where the pipe emerges from the floor.
Reduced clearance protective assembly (308.2) IFGC 2015 Section 308.2
Clearance reduction may be based on a method in Table 308.2 or on a manufactured assembly listed and labeled in accordance with UL 1618.
Maximum design operating pressure inside buildings (402.6) IFGC 2015 Section 402.6
Piping inside buildings is limited to 5 psig design operating pressure except where the system is welded, is in a ventilated chase, is a temporary construction installation, serves agricultural equipment, complies with NFPA 58 for LP-gas above 20 psi, or is located in areas used exclusively for industrial processing/heating, research, warehousing, or boiler/mechanical rooms.
Standard method for indoor combustion air (304.5, 304.5.1) IFGC 2015 Sections 304.5 and 304.5.1
Where the structure's air infiltration rate is not known, the space must have a minimum volume of 50 cubic feet per 1,000 Btu/h of the total input rating of all appliances in the space.
One-permanent-opening method for outdoor combustion air (304.6.2) IFGC 2015 Section 304.6.1
Where one permanent opening commencing within 12 inches of the top of the enclosure supplies combustion air, the appliance must have clearances of not less than 1 inch from the sides and back and 6 inches from the front.
Mechanical combustion air supply system (304.9) IFGC 2015 Section 304.9
Where all combustion air is provided by a mechanical air supply system, outdoor air must be supplied at not less than 0.35 cfm per 1,000 Btu/h of total appliance input, and Section 304.9.2 requires each appliance to be interlocked with the air supply system.
Combustion air through stud/joist spaces (304.11, Item 1 Exception) IFGC 2015 Section 304.11, Item 1 Exception
Unobstructed stud and joist spaces within dwelling units may convey combustion air provided not more than one required fireblock is removed; all other duct provisions of Section 304.11 still apply.
Alternative area method for chimney venting (503.5.5, Item 3) IFGC 2015 Section 503.5.5
For a chimney serving two draft-hood-equipped appliances, the effective flue area shall be not less than the larger draft hood outlet area plus 50 percent of the smaller draft hood outlet area, and not greater than seven times the smallest draft hood outlet area.
Vent offset limits for alternative-method-sized Type B/L vents (503.6.9.2) IFGC 2015 Section 503.6.9.2
Type B and L vents sized by Item 2 or 3 of Section 503.6.9.1 must run generally vertically with offsets not exceeding 45 degrees, except that not more than one 60-degree offset is permitted; any angle greater than 45 degrees from vertical is considered horizontal.
Residential-type vent connector materials (503.10.2.3) IFGC 2015 Section 503.10.2.3
For connectors not passing through attics, crawl spaces or other unconditioned areas, galvanized sheet steel shall be not less than 0.018 inch thick, 1100 or 3003 alloy aluminum sheet not less than 0.027 inch, and stainless steel sheet not less than 0.012 inch (0.0304 inch is the minimum for galvanized single-wall metal pipe vents under 503.7.1).
Formulas to Know
Convert appliance input to gas demand and back (natural gas, 1,000 Btu per cubic foot)
cfh = Btuh ÷ 1,000; Btuh capacity = table cfh × 1,000 (e.g., 40,000 + 65,000 + 30,000 = 135,000 Btuh → 135 cfh; 247 cfh → 247,000 Btuh)Spare (or short) capacity of an installed pipe
Spare cfh = table capacity at that length − appliance demand (e.g., 247 − 35 = 212 cfh spare; 44 − 40 = 4 cfh spare; 117 − 40 = 77 cfh spare)Table row selection under the longest length method (Table 402.4(2), 0.5 in. w.c. drop)
Measure meter to the most remote outlet (sum of main runs); if the table has no row for that length, use the next longer row, and apply that one row to every section and branch (e.g., 75 ft → 80-ft row; 70 ft → 70-ft row)Table row selection under the branch length method
Each branch uses its own meter-to-outlet length = main length to its tee + branch length, rounded up to the next table row (e.g., 15 + 5 = 20 ft → 20-ft row; 30 + 15 = 45 ft → 50-ft row; 20 + 15 = 35 ft → 40-ft row)Section load in a multi-outlet system
Each section carries the sum of the inputs of all outlets downstream of it, divided by 1,000 (e.g., section B serving outlets 2 and 3: 40,000 + 40,000 = 80,000 Btuh = 80 cfh; past the last tee only the last appliance remains)Minimum pipe size selection from the table
In the governing length row, pick the smallest diameter whose capacity equals or exceeds the section demand (e.g., 340 cfh at 80 ft: 1 in = 220 cfh too small, 1-1/4 in = 452 cfh OK)Maximum full-scale range of a mechanical test gauge
Highest end of gauge scale ≤ 5 × test pressure (e.g., 3 psig test → 15 psig maximum range)Minimum room volume, standard method for indoor combustion air
Volume = (total appliance input Btu/h ÷ 1,000) × 50 cubic feet (e.g., 80,000 + 40,000 = 120,000 → 6,000 cu ft)Free area of each outdoor combustion air opening, two-permanent-openings method
Direct to outdoors or through vertical ducts: 1 sq in per 4,000 Btu/h of total input per opening (120,000 ÷ 4,000 = 30 sq in each); horizontal ducts: 1 sq in per 2,000 Btu/hMechanical combustion air supply rate and furnace return air area
Mechanical supply = total input ÷ 1,000 × 0.35 cfm (400,000 Btu/h → 140 cfm); return/outdoor air area = furnace OUTPUT ÷ 1,000 × 2 sq in (120,000 Btu/h output → 240 sq in)