Exam Cheat Sheet · Quick Reference
Idaho HVAC Specialty Journeyman Exam
Idaho · PSI Services Contractor
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
120 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Idaho State Portion 50 questions
2018 International Fuel Gas Code (IFGC) - Chapter 1
6 Q · 12%
Scope of code applicability for fuel gas piping systems and appliancesInstallations and systems excluded from IFGC scopePermit requirements, application process, and exemptionsDuties and powers of the code official including inspections and right of entryRequired inspection types: underground, rough-in, and finalViolations, stop work orders, and unsafe installation proceduresApplicability rules for existing installations, alterations, and repairsPermit expiration, extension, suspension, and revocation
2018 International Fuel Gas Code (IFGC) - Chapter 2
6 Q · 12%
Definitions of appliance types and classifications (vented, unvented, fan-assisted, automatically controlled)Venting system terminology and vented appliance categories (Category I–IV, Type B, BW, L, special gas vents)Gas piping system terminology (piping, tubing, connectors, valves, regulators, point of delivery)Combustion-related definitions (combustion air, combustion products, draft, draft hood, flue, flue gases)Pressure regulator types and definitions (service pressure, line gas pressure, MP regulator, monitoring, series)Valve types and definitions (appliance shutoff, automatic, manual reset, service shutoff, main burner control)Chimney and vent connector definitions (factory-built, masonry, metal chimneys; barometric draft regulator)Fuel gas and measurement definitions (fuel gas types, BTU, cubic foot, specific gravity, demand, pressure drop)
2018 International Fuel Gas Code (IFGC) - Chapter 3
7 Q · 14%
Combustion air requirements and calculation methods (indoor, outdoor, and combination methods)Appliance location restrictions and prohibited locationsClearances to combustible construction and clearance reduction methodsAccess and service space requirements for appliances in attics, under-floor spaces, and roofsElectrical bonding requirements for gas piping and CSSTCondensate disposal systems, materials, and drain requirementsAppliance installation requirements including ignition source elevation in garagesListing, labeling, and label information requirements for appliances
2018 International Fuel Gas Code (IFGC) - Chapter 4
9 Q · 18%
Gas pipe sizing methods and table selection (longest length, branch length, hybrid pressure)Allowable pressure drop and maximum operating pressure limits for piping systemsApproved piping materials and tubing types (steel, copper, CSST, polyethylene, aluminum)Pressure testing requirements, test medium, test pressure values, and test durationPiping installation requirements (prohibited locations, underground burial depth, protection against physical damage)Shutoff valve placement and requirements for appliances, meters, and multiple-tenant systemsPurging procedures for piping systems (indoor vs. outdoor discharge, combustible gas indicators)Piping support intervals and overpressure protection device requirements
2018 International Fuel Gas Code (IFGC) - Chapter 5
8 Q · 16%
Venting system type selection and appliance category matching (Table 503.4)Sizing of Category I venting systems using tables (Section 504)Vent and chimney termination location requirementsVent connector materials, clearances, and installation requirementsGas vent types (Type B, BW, L) installation and termination rulesAppliances not required to be vented and aggregate input limitsMasonry chimney requirements, lining systems, and inspectionDraft hoods, draft controls, and mechanical draft system requirements
2018 International Fuel Gas Code (IFGC) - Chapter 6
7 Q · 14%
Installation requirements and listing standards for specific appliancesClearances to combustible materials for specific appliancesClothes dryer exhaust duct requirements including maximum length and fitting equivalentsUnvented room heater restrictions including prohibited locations and oxygen-depletion safety systemsVented wall furnace and floor furnace placement and clearance requirementsForced-air warm-air furnace prohibited return-air sourcesDuct furnace and unit heater installation and ductwork requirementsSauna heater location, combustion air, and heat/time controls
2018 International Fuel Gas Code (IFGC) - Chapter 7
7 Q · 14%
Gaseous hydrogen piping materials, design, and installation requirementsPressure relief device requirements and configurationTesting of hydrogen piping systems (hydrostatic and pneumatic leak tests)Purging procedures for gaseous hydrogen piping systemsCompressed gas container, cylinder, and tank requirementsLocation requirements for indoor and outdoor gaseous hydrogen systemsPiping identification, marking, and prohibited locationsOperation and maintenance of gaseous hydrogen systems
Key Distinctions
IFGC scopevsInternational Residential Code scope
The IFGC governs fuel gas installations generally, but per the Section 101.2 Exception detached one- and two-family dwellings and townhouses not more than three stories high with separate means of egress (and their accessory structures) comply with the International Residential Code instead.
IFGC 2018 Section 101.2 ExceptionNatural gas piping operating pressure limitvsLP-gas piping operating pressure limit
Per Section 101.2.2 the code covers natural gas piping systems operating at 125 psig or less, while LP-gas piping systems are covered at 20 psig or less (except as provided in Section 402.7).
IFGC 2018 Section 101.2.2General requirementvsSpecific requirement
Under Section 102.1, where a general and a specific requirement conflict, the specific requirement governs.
IFGC 2018 Section 102.1Rough-in inspectionvsFinal inspection
Per Section 107.2 the rough-in inspection is made after roof, framing, fireblocking and bracing are in place and concealed components are complete but before wall/ceiling membranes, while the final inspection is made upon completion of the installation (the third required inspection being the underground inspection before backfill).
IFGC 2018 Section 107.2Category I vented appliancevsCategory IV vented appliance
Per Section 202, Category I operates with nonpositive vent static pressure and a vent gas temperature that avoids excessive condensate, while Category IV operates with positive vent static pressure and a vent gas temperature capable of causing excessive condensate production.
IFGC 2018 Chapter 2, Section 202Low-heat (residential) appliancevsMedium-heat appliance
Per Section 202, a low-heat appliance has flue-entrance products of combustion at 1,000°F or less, while a medium-heat appliance is more than 1,000°F but not greater than 2,000°F.
IFGC 2018 (Idaho) Chapter 2, Section 202Steam heating boilervsHot water heating boiler
Per Section 202, a steam heating boiler generates steam at a pressure not exceeding 15 psig, while a hot water heating boiler generates no steam and operates at water pressure not exceeding 160 psig and water temperature not exceeding 250°F at or near the boiler outlet.
IFGC 2018 Chapter 2, Section 202Unvented room heater in a bathroomvsUnvented room heater in a bedroom
Per Section 303.3, a single wall-mounted unvented room heater in a bathroom is limited to 6,000 Btu/h input, while in a bedroom it is limited to 10,000 Btu/h (equipped per Section 621.6 with the room meeting the volume criteria of Section 304.5).
IFGC 2018 Section 303.3Appliance in a private garagevsAppliance in a public garage
Per Sections 305.4/305.5, private-garage appliances require a minimum 6 feet clearance above the floor, while public-garage appliances must be not less than 8 feet above the floor and, where vehicles can pass under, not less than 1 foot higher than the tallest vehicle garage door opening.
IFGC 2018 Section 305.5Combustion air openings communicating directly with outdoors or through vertical ductsvsCombustion air openings through horizontal ducts
Per Section 304.6.1 (two-permanent-openings method), direct/vertical openings need 1 square inch per 4,000 Btu/h each, while horizontal ducts need 1 square inch per 2,000 Btu/h each.
IFGC 2018 Section 304.6.1Longest length method (Section 402.4.1)vsBranch length method (Section 402.4.2)
Under the longest length method every section, including branches, is sized from the table row for the system's longest total length, while under the branch length method each branch is sized using its own measured length from the meter.
IFGC Section 402.4.1, Longest Length Method; Table 402.4(2), Schedule 40 Metallic Pipe (natural gas, 0.5 in. w.c. drop)Straight (measured) duct lengthvsTotal equivalent length
Straight length is the sum of the labeled straight segments only, while total equivalent length adds the elbow (fitting) equivalent-length allowances to that straight length.
BrazingvsSoldering
Per Section 202, brazing uses a nonferrous filler metal with a melting point above 1,000°F but below that of the base metal, which is the temperature threshold that distinguishes it from soldering.
IFGC 2018 (Idaho) Chapter 2, Section 202Key Terms
Bonding jumper IFGC 2018 (Idaho) Chapter 2, Section 202
A conductor installed to electrically connect metallic gas piping to the grounding electrode system (IFGC Section 202).
Demand IFGC 2018 Chapter 2 Definitions
The maximum amount of gas input required per unit of time, usually expressed in cubic feet per hour or Btu/h (IFGC Chapter 2).
Oxygen depletion safety shutoff system (ODS) IFGC 2018 (Idaho) Chapter 2, Section 202
A system designed to shut off the gas supply to the main and pilot burners if oxygen in the surrounding atmosphere is reduced below a predetermined level (IFGC Section 202).
Unvented appliance IFGC 2018 Chapter 2 Definitions
An appliance designed or installed so that the products of combustion are not conveyed by a vent or chimney directly to the outside atmosphere (IFGC Chapter 2).
Low-heat appliance (residential appliance) IFGC 2018 (Idaho) Chapter 2, Section 202
Any appliance whose products of combustion at the point of entrance to the flue under normal operating conditions are 1,000°F (538°C) or less (IFGC Section 202).
Medium-heat appliance IFGC 2018 (Idaho) Chapter 2, Section 202
Any appliance whose products of combustion at the flue entrance under normal operating conditions exceed 1,000°F but are not greater than 2,000°F (IFGC Section 202).
Gaseous hydrogen system IFGC 2018 (Idaho) Chapter 7, Section 702.1
An assembly designed to generate, store, contain, distribute or transport a nontoxic gaseous hydrogen mixture having at least 95 percent hydrogen by volume and not more than 1 percent oxygen by volume (IFGC Section 702.1).
Permit expiration IFGC 2018 Section 106.5.3
Per Section 106.5.3, a permit expires and becomes null and void if the authorized work is not commenced within 180 days of the permit date, or is suspended or abandoned for 180 days after commencement.
Work without a permit penalty IFGC 2018 Section 106.6.1
Per Section 106.6.1, a person commencing work before obtaining the necessary permits is subject to 100 percent of the usual permit fee in addition to the required permit fees.
Emergency replacement permit application IFGC 2018 Section 106.1 Exception
Per the Section 106.1 Exception, where appliance/equipment replacements or repairs must be performed in an emergency, the permit application shall be submitted within the next working business day of the Department of Inspection.
Change of occupancy certification IFGC 2018 Section 102.5
Per Section 102.5, the code official shall certify that a structure undergoing a change of occupancy meets the intent of the code provisions for the proposed new occupancy and creates no hazard to public health, safety or welfare.
Undefined terms IFGC 2018 Chapter 2, Section 201.3
Per Section 201.3, terms not defined in the IFGC but defined in the IBC, IFC, IMC or IPC have the meanings ascribed in those codes.
Basis for gas pipe sizing IFGC 2018 Section 402.2
Per Section 402.2, the total connected hourly load assuming all appliances could operate at full capacity simultaneously is the basis for pipe sizing (sizing based on established diversity of load is permitted), and flow must be adjusted for altitude above 2,000 feet.
Minimum supply pressure requirement IFGC 2018 Section 402.1
Per Section 402.1, piping systems must be sized and installed to meet maximum demand and supply gas to each appliance inlet at not less than the minimum supply pressure required by the appliance.
Existing piping capacity check IFGC 2018 Section 401.4
Per Section 401.4, where an additional appliance is to be served, the existing piping must be checked for adequate capacity for all appliances served and enlarged, or separate adequate piping provided, if inadequate.
Gas piping identification IFGC 2018 Section 401.5
Per Section 401.5, exposed piping other than steel pipe must be identified with a yellow label marked 'Gas' in black letters at intervals not exceeding 5 feet; per Section 401.7 piping from multiple meter installations must be permanently identified by the installer, and per Section 401.6 systems serving separate consumers must not be interconnected on the outlet side of the meters.
Combustion air opening minimum dimension IFGC 2018 (Idaho) Section 304.5.3.1
Per Sections 304.5.3.1 and 304.6, the minimum dimension of air openings shall be not less than 3 inches (not 4 inches).
Mechanical combustion air supply interlock IFGC 2018 (Idaho) Section 304.9.2
Per Section 304.9.2, where all combustion air is provided by a mechanical air supply system, each appliance served shall be interlocked with that system to prevent main burner operation when the air supply system is not operating (mandatory, not optional).
Formulas to Know
Gas demand in cubic feet per hour from Btu/h input (natural gas)
cfh = appliance input (Btu/h) ÷ 1,000; total demand = sum of all appliance cfh (e.g., (65,000 + 40,000 + 50,000) ÷ 1,000 = 155 cfh)Indoor combustion air minimum required volume — Standard Method (Section 304.5.1)
Volume = 50 cubic feet per 1,000 Btu/h of appliance input (80,000 Btu/h → 80 × 50 = 4,000 cu ft); known air-infiltration-rate method may not use an infiltration rate greater than 0.60 ACHOutdoor combustion air — free area of EACH opening, two-permanent-openings method (Section 304.6.1)
Direct to outdoors or vertical ducts: total input Btu/h ÷ 4,000 (120,000 ÷ 4,000 = 30 sq in each); horizontal ducts: total input Btu/h ÷ 2,000 (200,000 ÷ 2,000 = 100 sq in each)Public garage appliance mounting height (Section 305.4)
Height = tallest vehicle garage door opening + 1 ft (and never less than 8 ft above floor); 10-ft door → 11 ftGas vent effective area for two draft-hood-equipped appliances — alternative method (Section 503.6.10.1, Item 3)
Vent effective area ≥ area of larger draft hood outlet + 50% of area of smaller draft hood outlet (30 + 0.50 × 20 = 40 sq in)Corrugated metallic chimney liner capacity reduction (Section 504.2.7)
Allowable capacity = 0.80 × table maximum capacity (20-percent reduction, which includes an allowance for one long-radius 90-degree turn at the bottom of the liner)Hydrogen piping pneumatic test pressure (Section 705.3.2)
For working pressures at or above 125 psig: test pressure ≥ 110% of maximum working pressure (1.10 × 200 psig = 220 psig)Hydrogen piping pressure test duration (Section 705.3.5)
Minimum 1/2 hour, and not less than 1/2 hour for each 500 cu ft of pipe volume or fraction thereof (1,200 ÷ 500 = 2.4 → 3 × 0.5 hr = 1.5 hours)Duct total equivalent length and friction loss
Total equivalent length = sum of straight segments + (number of elbows × elbow equivalent length) = (28+22+15) + (2 × 25) = 115 ft; Friction loss = (total equivalent length ÷ 100) × friction rate = 1.15 × 0.10 = 0.115 in. WCMixed-air temperature and outdoor-air percentage
T_mix = (Return CFM × Return Temp + Outdoor CFM × Outdoor Temp) ÷ Total CFM = (3,000×60 + 1,000×92) ÷ 4,000 = 68.0 °F; OA% = Outdoor CFM ÷ Total CFM = 1,000 ÷ 4,000 = 25%; Total CFM = sum of entering streams (3,000 + 1,000 = 4,000)Additional refrigerant charge for a long line set
Feet needing charge = total line set length − 15 ft covered by factory charge (65 − 15 = 50 ft); Added charge = feet × 0.6 oz/ft = 30.0 oz; ÷ 16 oz/lb ≈ 1.9 lb