ICC G31 Journeyman Mechanical Exam (2018 IMC/IFGC)
Practice at the real exam's pace
Every practice exam shows your time per question against the real exam's clock (3:36 here), and each topic lands in one of these:
What's on the exam
Questions per topic, out of 50Topics
Administration General Regulations
Key Concepts
Scope and applicability - The code regulates design, installation, maintenance, alteration and inspection of permanently installed mechanical systems; fuel gas piping, fuel gas-fired appliances and their venting are regulated by the International Fuel Gas Code (IMC 101.2). - Where a general requirement conflicts with a specific requirement, the specific requirement governs. The "most restrictive governs" rule applies only where different sections specify different materials, methods of construction or other requirements (IMC 102.1, Page 1). - Where a code provision is less restrictive than the conditions of the listing or the manufacturer's installation instructions, the listing conditions and manufacturer's instructions apply (IMC 304.2, Page 23; parallel exception in 102.8). - A provision of the code shall not require removal, alteration or abandonment of a mechanical system lawfully in existence at adoption (IMC 102.2); additions, alterations and repairs must conform to new-system requirements without forcing full compliance of the existing system, and shall not make it unsafe, hazardous or overloaded (IMC 102.4).
Appliances & Mechanical Equipment
Key Concepts
Gas-fired specific appliances (2018 IFGC, Chapter 6) - Vented wall furnaces: a door shall not swing within 12 inches (305 mm) of an air inlet or air outlet, measured at right angles to the opening; doorstops or door closers shall not be installed to obtain this clearance (Section 608.4). Tested to ANSI Z21.86/CSA 2.32 (608.1). - Vented gas fireplaces (decorative appliances) are tested to ANSI Z21.50/CSA 2.22 (Section 604.1). Forced-air warm-air furnaces are tested to ANSI Z21.47/CSA 2.3 or UL 795 (Section 618.1). Unit heaters are tested to ANSI Z83.8/CSA 2.6 (620.1). - Unvented room heaters: input rating shall not exceed 40,000 Btu/h (11.7 kW) (621.3); prohibited in Groups A, E and I (621.4); aggregate input of all unvented appliances shall not exceed 20 Btu/h per cubic foot of room/space volume (621.5); oxygen-depletion-sensitive shutoff must shut off the gas supply to the main and pilot burners when oxygen in the surrounding atmosphere is depleted to the manufacturer's specified percent concentration, but not lower than 18 percent (621.6). - Suspended unit heaters: hangers and brackets shall be of noncombustible material (620.2); clearances to combustibles not less than 18 inches at the sides, 12 inches at the bottom and…
Exhaust and Ventilation Systems
2018 International Mechanical Code — Chapter 4 (Ventilation) and Chapter 5 (Exhaust Systems)
Key Concepts
Exhaust discharge locations (IMC 501.3.1, p. 41) - Ducts conveying explosive or flammable vapors, fumes or dusts: not less than 30 feet from property lines; 10 feet from operable openings into buildings; 6 feet from exterior walls and roofs; 30 feet from combustible walls and operable openings into buildings that are in the direction of the exhaust discharge; 10 feet above adjoining grade. - Other product-conveying outlets: 10 feet from property lines; 3 feet from exterior walls and roofs; 10 feet from operable openings; 10 feet above adjoining grade. - All environmental air exhaust: 3 feet from property lines; 3 feet from operable openings into buildings for occupancies other than Group U; 10 feet from mechanical air intakes. Such exhaust is not considered hazardous or noxious.
Exhaust opening protection (IMC 501.3.2, pp. 41–42). Exhaust openings terminating outdoors shall be protected with corrosion-resistant screens, louvers or grilles; openings sized not less than 1/4 inch and not larger than 1/2 inch, and protected against local weather conditions.
Duct Systems
2018 International Mechanical Code, Chapter 6 — Duct Systems
Key Concepts
Return air (Section 601.5, p. 70) - Return air openings shall not be located less than 10 feet, measured in any direction, from an open combustion chamber or draft hood of another appliance in the same room or space (Item 1). - Return air shall not be taken from a closet, bathroom, toilet room, kitchen, garage, boiler room, furnace room or unconditioned attic (Item 7). Exception 1: return air from a kitchen is permitted where the openings serve the kitchen and are not less than 10 feet from cooking appliances. Exception 2: dedicated forced-air systems serving only the garage may take return air from the garage. - The amount of return air from any room shall be not greater than the supply air delivered to that room (Item 3).
Egress elements (Section 601.2, p. 69) — Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts. Exception 3 permits corridors to convey return air where located within tenant spaces of 1,000 square feet (93 m²) or less. Exception 2 covers dwelling units; Exception 1 covers corridor makeup air; Exception 4 covers health care pressurization.
Combustion Air
Key Concepts
Scope and code split - Combustion and dilution air for gas-fired appliances is governed by IFGC Section 304 (IFGC 301.1.1; IMC 701.1). Combustion air for solid fuel-burning appliances follows the manufacturer's installation instructions, and oil-fired appliances follow NFPA 31 (IMC 701.1). - IMC Chapter 7 methods do not apply to fireplaces, fireplace stoves and direct-vent appliances (IMC 701.1). - Dampered openings: volume, smoke or fire dampers in combustion air openings must be interlocked with the firing cycle of the appliances served, to prevent operation of any appliance drawing combustion air from the space when any damper is closed. Manual dampers shall not be installed in combustion air ducts (IMC 701.2).
Indoor combustion air (IFGC 304.5) - Required indoor volume is determined by Section 304.5.1 or 304.5.2; where the air infiltration rate is known to be less than 0.40 ACH, Section 304.5.2 shall be used. - Standard method (304.5.1): minimum 50 cubic feet per 1,000 Btu/h of appliance input rating. - Known air-infiltration-rate method (304.5.2): for the calculation, an infiltration rate greater than 0.60 ACH shall not be used in Equations 3-1 and 3-2. - Indoor openings (304.5.3.1/304.5.3.2): same story — each opening 1 in² per 1,000 Btu/h,…
Chimneys and Vents
Key Concepts
- Venting required. Every appliance shall discharge products of combustion to the outdoors, except appliances exempted by Section 501.8 (IFGC 501.2). Exempt appliances include ranges, hot plates and laundry stoves, Type 1 clothes dryers, refrigerators, counter appliances, room heaters listed for unvented use, direct-fired makeup air heaters, and specialized limited-input appliances such as laboratory burners and gas lights (501.8).
- Unvented aggregate input. Where appliances in Items 5 through 11 are installed so the aggregate input rating exceeds 20 Btu per hour per cubic foot of room volume, one or more shall be vented so the remaining unvented appliances do not exceed 20 Btu/h/ft³ (501.8). Adjoining rooms connected by a doorway/archway that cannot be closed may be included in the volume.
- Chimney entrance. Connectors shall connect to a masonry chimney flue not less than 12 inches above the lowest portion of the interior of the chimney flue (IFGC 501.9; IMC 801.12; see also 503.10.10).
- Chimney termination (503.5.4). Residential-type or low-heat: not less than 3 feet above the highest point of roof passage and not less than 2 feet higher than any portion of a building within 10 feet horizontally. Medium-heat: not less than 10 feet…
Fuel Supply Systems
Key Concepts
Materials (IFGC 403) - Cast-iron pipe shall not be used (403.4.1). Steel, stainless steel and wrought-iron pipe shall be not lighter than Schedule 10, complying with ASME B36.10M and ASTM A53/A53M, A106 or A312 (403.4.2). - Copper and copper alloy shall not be used where the gas contains more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet (403.4.3, 403.5.3). Copper tubing shall comply with Standard Type K or L of ASTM B88 or ASTM B280 (403.5.3). - Aluminum-alloy pipe shall comply with ASTM B241, alloy 5456 prohibited, and shall not be used in exterior locations or underground (403.4.4; tubing, 403.5.4). - CSST shall be listed in accordance with ANSI LC 1/CSA 6.26 (403.5.5). Polyethylene pipe shall conform to ASTM D2513 and be marked "Gas" and "ASTM D2513" (403.6).
Joints and fittings (IFGC 403.9–403.10) - Threads shall be taper pipe threads complying with ASME B1.20.1 (403.9). - Schedule 40 and heavier pipe joints: threaded, flanged, brazed, welded or press-connect listed to ANSI LC-4/CSA 6.32. Pipe lighter than Schedule 40: press-connect, flanges, brazing or welding (403.10.1). - Brazing material for nonferrous pipe and for copper tubing joints shall have a melting point **in…