Exam Cheat Sheet · Quick Reference
ICC F31 Journeyman Mechanical Exam (2015 IMC/IFGC)
National · 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
50
Passing score
70%
Exam time
180 min
Administered by
Pearson Vue
Format
Reference materials allowed
National State Portion 50 questions
General Requirements
23 Q · 46%
Permit requirements and exemptionsCode official authority and dutiesInspections and testing requirementsAppliance listing, labeling, and approval requirementsEquipment and appliance location restrictionsAccess and service space requirements for appliancesClearances to combustible construction and clearance reduction methodsKey IMC definitions and terminologyGeneral RegulationsScope and AdministrationDefinitions
Appliances and Equipment
7 Q · 14%
Heating appliance installation requirements and clearances (wall furnaces, floor furnaces, unit heaters, duct furnaces)Clothes dryer exhaust duct systems (materials, length limits, termination, makeup air)Boiler installation, safety devices, and pressure relief valvesUnvented room heater restrictions (prohibited locations, oxygen-depletion shutoff, input rating limits)Forced-air warm-air furnace requirements (return air sources, duct sizing, prohibited return air locations)Cooking appliance installation (domestic vs. commercial, vertical clearances, venting)Sauna heater installation (temperature controls, combustion air, ventilation openings)Water heater and pressure vessel requirements (standards, expansion tanks, gauges, dual-use space heating)Specific Appliances, Fireplaces and Solid Fuel-Burning EquipmentBoilers, Water Heaters and Pressure VesselsSpecific Appliances
Exhaust and Ventilation Systems
1 Q · 2%
Exhaust discharge location and minimum separation distancesCommercial kitchen Type I and Type II hood requirements and exhaust ratesClothes dryer exhaust duct materials, length limits, and installation requirementsHazardous exhaust systems design and duct construction requirementsMechanical ventilation outdoor airflow rates by occupancy classificationMakeup air requirements for exhaust systemsSmoke control system design methods and equipment requirementsEnergy recovery ventilation system applications and prohibited usesExhaust Systems
Duct Systems
7 Q · 14%
Duct construction materials and classification (metallic, nonmetallic, flexible)Duct joints, seams, and connection sealing requirementsPlenum construction and material flame/smoke rating requirementsFire dampers, smoke dampers, and combination dampers — ratings, actuation, and placementDuct insulation, vapor retarders, and surface temperature limitsReturn air opening restrictions and prohibited locationsSmoke detection system controls for air distribution systemsUnderground duct installation requirements
Combustion Air
3 Q · 6%
Indoor combustion air volume requirements (standard method and known air-infiltration-rate method)Outdoor combustion air opening methods (two-permanent-openings and one-permanent-opening)Combination indoor and outdoor combustion air sizing and calculationMechanical combustion air supply systems and appliance interlock requirementsCombustion air duct construction, materials, and installation requirementsLouvers, grilles, and screens — net free area calculation and motorized louver interlockMakeup air provisions for exhaust fans and interfering equipmentScope and applicability of combustion air methods by appliance and fuel type (IMC vs. IFGC)
Chimneys and Vents
3 Q · 6%
Vent system types and applications (Type B, BW, L, single-wall metal pipe)Chimney and vent sizing methods for Category I appliances using sizing tablesVent and chimney termination location requirementsVent connector materials, construction, clearances, and installation requirementsDraft hoods, draft controls, and automatically operated vent dampersFactory-built chimney listing, installation, and termination requirementsFlue lining systems for masonry chimneys (clay tile, listed liner systems)Appliances not required to be vented and unvented appliance input limitsChimneys and Vents
Fuel Supply Systems
1 Q · 2%
Gas pipe sizing methods and sizing tables (longest length, branch length, hybrid pressure)Allowable pressure drop and maximum design operating pressure limitsApproved piping and tubing materials (steel, copper, CSST, polyethylene, aluminum)Piping joints, fittings, and connection requirements by material typePiping installation requirements (prohibited locations, underground burial depth, protection from damage, support intervals)Shutoff valves, pressure regulators, and overpressure protection devicesPressure testing, leak detection, and purging procedures for gas piping systemsFuel oil piping materials, joints, valves, testing, and system installation requirementsGas Piping Installations
Special Requirements
3 Q · 6%
Refrigerant classification and maximum allowable quantities per occupancy typeMachinery room general and special requirements (ventilation, emergency shutoff, refrigerant detectors)Refrigerant piping materials, joints, location restrictions, and field pressure testingRefrigerant system classification (low-probability vs. high-probability systems)Hydronic piping materials, fittings, joints, and pressure testing requirementsEmbedded piping installation and thermal barrier requirements for radiant systemsGround-source heat pump loop system piping, joints, shutoff valves, and testingSolar system installation requirements (pressure/temperature relief, freeze protection, heat transfer fluids, and roof-mounted collectors)RefrigerationHydronic Piping
Electrical
2 Q · 4%
Electrical wiring, controls, and connections compliance with NFPA 70Label information requirements for electrical equipment and appliances (volts, amperes, motor phase)Electrical receptacle outlet requirements for appliances in attics and underfloor spacesElectrical receptacle outlet requirements for equipment on roofs or elevated structuresLuminaire and switch requirements at appliance access passageway openings
Key Distinctions
Equipment supported on a slab at gradevsEquipment suspended above grade
IMC 304.10 requires grade-set equipment to sit on a level slab or approved material extending not less than 3 inches above adjoining grade, while suspended equipment must be not less than 6 inches above adjoining grade.
IMC 2015 Section 304.10Longest 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 length to the most remote outlet (rounded up to the next longer table row), whereas the branch length method sizes each branch using its own length from the meter and sizes main sections by the longest run served.
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 shutoff valve at a manifoldvsAppliance shutoff valve in the same room as the appliance
Per IFGC 409.5.3 a manifold-mounted shutoff must be within 50 feet of the appliance served and readily accessible and permanently identified, while IFGC 409.5.1 applies the 6-foot figure to a shutoff located in the same room as the appliance.
IFGC 2015 Section 409.5.3Single-wall metal connector (unengineered system)vsType B double-wall connector
Per IFGC 503.10.8 the maximum horizontal length of a single-wall connector is 75 percent of the chimney or vent height, while a Type B double-wall connector is permitted 100 percent of that height.
IFGC 2015 Section 503.10.8Gas-fired water heatervsWater heater using fuels other than fuel gas
IFGC 624.1 covers gas-fired water heaters (tested to ANSI Z21.10.1 and ANSI Z21.10.3), but water heaters utilizing fuels other than fuel gas are regulated by the International Mechanical Code.
IFGC 2015 Section 624.1Unvented room heater input cap (IFGC 621.3)vsAggregate unvented input by room volume (IFGC 621.5)
IFGC 621.3 caps any single unvented room heater at 40,000 Btu/h input, while IFGC 621.5 separately limits the aggregate input of all unvented appliances to 20 Btu/h per cubic foot of space volume; whichever is lower governs.
IFGC 2015 Sections 621.3 and 621.5Attic passageway, general rulevsAttic passageway, Exception 2
IMC 306.3 limits the attic passageway to 20 feet measured along its centerline, but Exception 2 permits up to 50 feet where the passageway is unobstructed and not less than 6 feet high and 22 inches wide for its entire length.
IMC 2015 Section 306.3, Exception 2Two permanent combustion air openings through horizontal ductsvsTwo openings direct/through vertical ducts, and the one-permanent-opening method
Per IFGC 304.6.1 horizontal-duct openings require 1 square inch per 2,000 Btu/h each, direct or vertical-duct openings require 1 square inch per 4,000 Btu/h, and the one-permanent-opening method requires 1 square inch per 3,000 Btu/h.
IFGC 2015 Section 304.6.1Metal louvers and grilles (free area unknown)vsWood louvers (free area unknown)
Per IFGC 304.10, where design and free area are not known, metal louvers and grilles are assumed to have 75-percent free area and wood louvers 25-percent free area.
IFGC 2015 Section 304.10Notching studs in nonbearing partitionsvsNotching studs in exterior walls and bearing partitions
IMC 302.3.2 permits notching a nonbearing partition stud (supporting no load other than the partition weight) up to 40 percent of its depth, while studs in exterior walls and bearing partitions are limited to 25 percent (60 percent is the bored-hole diameter limit for nonbearing partition studs).
IMC 2015 Section 302.3.2Notches in the top or bottom of wood joistsvsNotches at joist ends and bored holes
IMC 302.3.1 limits top/bottom notches to one-sixth the joist depth and prohibits them in the middle third of the span, while end notches are limited to one-fourth and bored holes to one-third the depth in diameter.
IMC 2015 Section 302.3.1Soldered jointvsBrazed joint
Per IMC 202, a soldered joint uses metallic mixtures or alloys melting between 400°F and 1,000°F, while brazed joints use filler metals melting above 1,000°F but below the base metal's melting point.
IMC 2015 Section 202 (Joint, Soldered)Thimble for a listed draft-hood appliance with a short open runvsThimble where not less than 6 feet of metal pipe runs in the open
IFGC 503.7.7 Item 1 requires a ventilated thimble not less than 4 inches larger in diameter for listed draft-hood appliances, but permits not less than 2 inches larger 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 (6-inch and 12-inch figures apply to unlisted draft-hood and residential/low-heat appliances).
IFGC 2015 Section 503.7.7IMC scopevsInternational Residential Code scope (IMC 101.2 Exception)
Mechanical systems in detached one- and two-family dwellings and in townhouses not more than three stories high with separate means of egress, and their accessory structures, follow the IRC rather than the IMC.
IMC 2015 Section 101.2Key Terms
Refrigeration capacity rating (IMC 202) IMC 2015 Section 202 (Refrigeration Capacity Rating)
1 horsepower, 1 ton, and 12,000 Btu/h (3.5 kW) all express the same refrigeration capacity.
Low-heat (residential) appliance (IMC 202, Appliance Type) IMC 2015 Section 202 (Appliance Type — Low-Heat Appliance)
An appliance whose combustion products at the flue entrance under normal operating conditions are 1,000°F or less; medium-heat is above 1,000°F but not more than 2,000°F and high-heat exceeds 2,000°F.
Standard air (IMC 202, Air) IMC 2015 Section 202 (Air)
Air at standard temperature and pressure, namely 70°F (21°C) and 29.92 inches of mercury (101.3 kPa).
Low-pressure hot-water-heating boiler (IMC 202) IMC 2015 Section 202 (Low-Pressure Hot-Water-Heating Boiler)
A boiler furnishing hot water at pressures not exceeding 160 psi and temperatures not exceeding 250°F (121°C).
Breathing zone (IMC 202) IMC 2015 Section 202 (Breathing Zone)
The region within an occupied space between planes 3 inches and 72 inches above the floor and more than 2 feet from the walls or from fixed air-conditioning equipment.
Refrigerated room or space (IMC 202) IMC 2015 Section 202 (Refrigerated Room or Space)
A room or space containing an evaporator or brine coil for the purpose of reducing or controlling the temperature in that space to below 68°F (20°C).
Permit exemption for self-contained refrigeration systems (IMC 106.2, Item 7) IMC 2015 Section 106.2
No mechanical permit is required for a self-contained refrigeration system containing 10 pounds (4.5 kg) or less of refrigerant or actuated by motors of 1 horsepower or less.
Permit expiration (IMC 106.4.3) IMC 2015 Section 106.4.3
A permit becomes null and void if the authorized work is not commenced within 180 days of the permit date or if work is suspended or abandoned for 180 days after commencing.
Appeal filing and board action (IMC 109.1, 109.3, 109.6) IMC 2015 Section 109.1
An appeal application must be filed on a form obtained from the code official within 20 days after the notice was served, the board must meet within 10 days of filing upon notice from the chairman, and three concurring votes of the five-member board are required to modify or reverse the code official's decision.
Operation before inspection of replacement heating appliances (IMC 107.2) IMC 2015 Section 107.2
Replacement heating equipment serving an occupied portion of a structure may be operated before inspection provided an inspection request is filed with the department not more than 48 hours after the replacement work is completed and before any portion is concealed.
Underground inspection exception (IMC 107.2) IMC 2015 Section 107.2
Underground piping must stay exposed until inspected, except ground-source heat pump loop systems tested per Section 1210.10, which are permitted to be backfilled prior to inspection.
Construction document penetration details (IMC 106.3.1) IMC 2015 Section 106.3.1
For buildings more than two stories in height, construction documents must indicate where mechanical system penetrations will be made and the materials and methods for maintaining required structural safety, fire-resistance rating and fireblocking.
Underfloor (crawl space) appliance lighting and power (IMC 306.4.1) IMC 2015 Section 306.4.1
An appliance in an underfloor space must have a luminaire controlled by a switch located at the required passageway opening and a receptacle outlet at or near the appliance location, per NFPA 70.
Central furnace working space in a compartment or alcove (IMC 306.1.1) IMC 2015 Section 306.1.1
A minimum 3-inch working space clearance is required along the sides, back and top, with the enclosing space being not less than 12 inches wider than the furnace.
Appliance in a pit or excavation (IMC 303.7; IFGC 609.4 floor furnace) IMC 2015 Section 303.7
Appliances in pits must not contact surrounding soil and the pit sides must be held back not less than 12 inches from the appliance; where a pit is excavated for a floor furnace, 12 inches minimum is required on all sides except the control side, which requires 18 inches.
Guard for rooftop equipment (IMC 304.11) and roof access (IMC 306.5) IMC 2015 Section 304.11
A required guard must extend not less than 30 inches beyond each end of components requiring service with its top not less than 42 inches above the adjacent elevated surface, and permanent interior or exterior access (not portable ladders) is required where personnel must climb higher than 16 feet above grade.
Protective shield plates (IMC 305.5) IMC 2015 Section 305.5
Where piping passes through bored or notched members less than 1 1/2 inches from the nearest edge, steel shield plates at least 0.0575 inch thick (No. 16 gage) must cover the area and extend not less than 2 inches above sole plates and below top plates.
Auxiliary drain pan (IMC 307.2.3, Item 1) IMC 2015 Section 307.2.3
An auxiliary drain pan with separate drain beneath a cooling coil must be at least 1 1/2 inches deep and not less than 3 inches larger than the unit or coil in width and length.
Ductless mini-split condensate (IMC 307.2.4.1) IMC 2015 Section 307.2.4.1
Ductless mini-split equipment that produces condensate must have an inline check valve in the drain line, or a trap.
Clothes dryer exhaust duct length (IMC 504.8.4.1 / 504.8.5; IFGC 614.8.5) IMC 2015 Section 504.8.4.1
Using the code's specified-length method the maximum duct length is 35 feet from the connection to the transition duct to the outlet terminal (reduced for fittings per Table 504.8.4.1), and where equivalent length exceeds 35 feet it must be identified on a permanent label or tag within 6 feet of the exhaust duct connection.
Unvented infrared radiant heater ventilation (IFGC 630.3) IFGC 2015 Section 630.3
Natural or mechanical means must supply outdoor ventilation air at not less than 4 cfm per 1,000 Btu/h of the aggregate input rating of all such heaters in the space, with exhaust openings above the level of the heaters.
Listed corrugated metallic chimney liner (IFGC 504.2.7) IFGC 2015 Section 504.2.7
Sized using the Type B vent tables with the maximum capacity reduced by 20 percent (0.80 × table maximum); the minimum capacity is used as listed.
Water heater sizing, relief valves, drain pans and scald protection (IFGC 624.1.1); combination water/space heating (IFGC 624.2) IFGC 2015 Section 624.1.1
These water heater requirements are in accordance with the International Plumbing Code, and a listed and labeled combination potable water heating/space heating appliance is installed per the manufacturer's instructions and the International Plumbing Code.
Referenced standards: NSF 14 (IMC 301.4) and ASHRAE/ACCA 183 (IMC 312.1) IMC 2015 Section 301.4
Plastic pipe, fittings and components must be third-party certified as conforming to NSF 14, and heating/cooling design loads for sizing systems, appliances and equipment are determined per ASHRAE/ACCA Standard 183 or an approved equivalent computation procedure.
Solid fuel-burning appliance clearance reduction (IMC 308.4.2.1) IMC 2015 Section 308.4.2.1
Where such appliances are labeled for clearances greater than 12 inches, Table 308.4.2 reduction methods shall not reduce the clearance to less than 12 inches; no reduction is permitted for appliances labeled at 12 inches or less.
Formulas to Know
Converting appliance input to gas demand for pipe sizing tables
cfh = Btu/h input ÷ 1,000 (natural gas); a section carries the sum of the loads of all outlets downstream of it (e.g., 40,000 + 30,000 = 70,000 Btuh = 70 cfh)Longest length method row selection (IFGC 402.4.1, Table 402.4(2))
Measure meter-to-most-remote-outlet length; if no exact table row exists use the next longer row (e.g., 75 ft → 80-ft row) and size every section of the system from that one rowBranch length method sizing (IFGC 402.4.2, Table 402.4(2))
Size each branch from its own total length from the meter rounded up to the next table row (e.g., 20 ft main + 15 ft branch = 35 ft → 40-ft row; 42-ft branch → 50-ft row); size main sections from the longest run they serve (e.g., 55 ft → 60-ft row)Fuel gas piping test pressure (IFGC 406.4.1)
Test pressure = 1.5 × 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)Aggregate unvented appliance input by space volume (IFGC 621.5, with 621.3 cap)
Max aggregate input = 20 Btu/h × room volume in cubic feet, including the volume of an adjacent space connected by a doorway/archway that cannot be closed (example: (1,800 + 700) × 20 = 50,000 Btu/h); any single unvented room heater is still capped at 40,000 Btu/hIndoor combustion air, standard method (IFGC 304.5 / 304.5.1)
Required volume = 50 cubic feet per 1,000 Btu/h of the combined input of all appliances in the space (example: 125,000 Btu/h → 125 × 50 = 6,250 cubic feet)Outdoor combustion air, two permanent openings through horizontal ducts (IFGC 304.6.1)
Each opening = total input ÷ 2,000 square inches of net free area (example: 140,000 ÷ 2,000 = 70 square inches each)Combination indoor/outdoor combustion air opening (IFGC 304.7.3 with 304.6.2)
Full one-opening area = total input ÷ 3,000 sq in; reduction factor = 1 − (available interior volume ÷ required volume); minimum outdoor opening = full area × reduction factor (example: 120,000/3,000 = 40 sq in; 1 − 3,600/6,000 = 0.4; 40 × 0.4 = 16 sq in, minimum dimension still not less than 3 inches)Gross opening size behind a grille of unknown free area (IFGC 304.10)
Gross area = required net free area ÷ 0.75 for metal louvers/grilles (example: 60 ÷ 0.75 = 80 square inches); wood louvers are assumed 25-percent free areaMechanical combustion air supply rate (IFGC 304.9)
Not less than 0.35 cfm per 1,000 Btu/h of total input (example: 400,000 ÷ 1,000 × 0.35 = 140 cfm); each appliance served must be interlocked with the supply system per 304.9.2Return/outdoor air opening area for a forced-air warm-air furnace (IFGC 618.2)
Not less than 2 square inches per 1,000 Btu/h of output rating capacity, and not less than the manufacturer's instructions require (example: 100,000 ÷ 1,000 × 2 = 200 square inches)Fire damper actuation temperature (IMC 607.3.3.1)
Approximately normal duct operating temperature + 50°F, but not less than 160°F (example: 100°F + 50°F = 150°F, so 160°F governs); the 350°F maximum applies only in a smoke control systemMaximum horizontal length of a single-wall connector (IFGC 503.10.8)
0.75 × chimney or vent height (example: 0.75 × 20 ft = 15 ft); Type B double-wall connector permitted 100 percent of the height