Denver Residential Mechanical (Class C) Exam (ICC F32, 2015 IRC) Practice Exam
ICC is retiring this exam. From December 1, 2026 it is no longer available for registration through Pearson VUE (ICC Exam Catalog, checked October 21, 2026). Check the ICC Exam Catalog or your licensing jurisdiction for the exam that replaces it.
Free Practice Exam
Test your knowledge with 10 questions from our pool of 20 free questions.
- 10 questions per attempt
- 30 minute time limit
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Full Practice Exam
Complete exam simulation matching the real Pearson VUE test format.
- 70 questions (same as real exam)
- 180 minute time limit
- 6 topic areas covered
- 317 questions in pool
- Detailed explanations
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Denver Residential Mechanical (Class C) (ICC F32, 2015 IRC) Practice Exam Guide
What's on the exam
Questions per topic, out of 70This practice exam is built around the official content outline for the Denver Residential Mechanical (Class C) (ICC F32, 2015 IRC) exam: General Requirements, Appliances and Equipment, Duct Systems, Combustion Air, Chimneys and Vents, Fuel Supply Systems.
There are two ways to practice. The free practice exam gives you 10 questions per attempt, and you can take it as many times as you like. The full practice exam gives you 70 questions on a 3 hours clock, with a new draw from our question bank each time.
General Requirements 22 items
Our study plan for this topic: Appliance access and working space clearances (attic, underfloor, alcove, and room installations); Clearances from combustible construction and clearance reduction methods; Appliance labeling requirements and nameplate information; Appliance installation requirements (anchorage, ignition source elevation, seismic strapping, garage protection); Mechanical administration: scope, existing system alterations, and maintenance responsibilities; Exhaust systems: clothes dryer exhaust ducts, range hoods, and mechanical ventilation rates; Hydronic piping materials, support intervals, testing requirements, and floor heating systems; Oil tank and oil piping installation, special piping storage systems, and solar thermal energy system requirements.
Appliances and Equipment 4 items
Our study plan for this topic: Equipment sizing requirements (ACCA Manual J and Manual S); Clearances, access, and serviceability requirements for heating and cooling equipment; Condensate disposal, auxiliary drain pans, and water-level monitoring devices; Refrigerant piping insulation, protection, and locking access port caps; Boiler safety controls, pressure-relief valves, gauges, and low-water cutoffs; Expansion tanks for hot water boiler systems; Water heater installation requirements, prohibited locations, and standards; Special appliances installation requirements (ranges, sauna heaters, fuel cell power plants).
Duct Systems 11 items
Our study plan for this topic: Duct construction standards and material requirements (above-ground and underground); Duct sealing — joints, seams, and connection fastening methods; Duct insulation materials — flame spread/smoke-developed ratings and R-value labeling; Duct support requirements by duct type; Use of stud wall cavities and joist spaces as air plenums; Return air opening restrictions and prohibited source locations; Under-floor plenum requirements and prohibitions; Independent garage HVAC systems — supply and return air restrictions.
Combustion Air 16 items
Our study plan for this topic: 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 provisions; Mechanical combustion air supply systems and appliance interlock requirements; Combustion air duct construction and installation requirements; Louvers, grilles, and screens for combustion air openings (net free area calculations); Combustion air requirements for solid-fuel, oil-fired, and gas-fired appliances by fuel type; Fuel Gas.
Chimneys and Vents 7 items
Our study plan for this topic: Venting system types and applications (Type B, Type BW, Type L, single-wall metal pipe, special gas vent); Chimney and vent termination height requirements; Vent connector installation requirements (slope, clearances, length, materials); Sizing of Category I appliance venting systems using IRC tables; Masonry chimney requirements (flue lining, cleanouts, connections, inspection); Factory-built chimney listing and installation requirements; Draft hoods, draft regulators, and automatically operated vent dampers; Fuel Gas.
Fuel Supply Systems 10 items
Our study plan for this topic: Gas piping materials and tubing types (steel, copper, CSST, polyethylene plastic); Gas pipe sizing methods and sizing tables (longest length, branch length, hybrid pressure); Piping system installation requirements (prohibited locations, underground burial depth, protection from physical damage); Pressure testing, leak detection, and purging procedures; Shutoff valves and flow controls (appliance shutoff valves, pressure regulators, excess flow valves); Electrical bonding requirements for gas piping (CSST bonding, bonding jumper specifications); Appliance connections and connectors (maximum length, prohibited penetrations, union requirements); Fuel oil storage tanks and piping systems (tank types, installation, fill/vent piping, shutoff valves).
Sample 1 — General Requirements
Question: The clearance-reduction table for specified forms of protection may not be used at all for solid-fuel-burning appliances that are listed for installation with minimum clearances of what dimension or less?
- A. 6 inches
- B. 9 inches
- C. 18 inches
- D. 12 inches
Correct Answer: D
Per IRC 2015 Section M1306.2.3, Table M1306.2 shall not be used to reduce the clearance required for solid-fuel appliances listed for installation with minimum clearances of 12 inches or less. For solid-fuel appliances listed with clearances greater than 12 inches, the table may not be used to reduce clearance below 12 inches.
Reference: IRC 2015 Section M1306.2.3
Sample 2 — Combustion Air
Question: A mechanical air supply system provides all of the combustion air from the outdoors for gas appliances located in a dwelling's utility room and delivers 35 cubic feet per minute. Based on the minimum supply rate required by code, what is the greatest total appliance input rating this system may serve?
- A. 120,000 Btu/h
- B. 35,000 Btu/h
- C. 100,000 Btu/h
- D. 350,000 Btu/h
Correct Answer: C
Per 2015 IRC Section G2407.9 (304.9), mechanically supplied combustion air must be provided from outdoors at not less than 0.35 cfm per 1,000 Btu/h of total input. 35 cfm ÷ 0.35 cfm = 100, so the system supports 100 × 1,000 = 100,000 Btu/h of total input rating.
Reference: IRC 2015 Section G2407.9 (304.9)
Sample 3 — Duct Systems
Question: An inspector asks how you determined the size of the return and transfer openings for a forced-air system you installed in a dwelling. Which basis for sizing is acceptable?
- A. ACCA Manual D or the manufacturer's instructions
- B. The free area of the supply registers served
- C. ACCA Manual J whole-house load calculation
- D. SMACNA HVAC Duct Construction Standards
Correct Answer: A
Per IRC 2015 Section M1602.2, Item 3, return and transfer openings shall be sized in accordance with the appliance or equipment manufacturers' installation instructions, Manual D, or the design of the registered design professional. Manual J is a load calculation method and SMACNA standards address duct construction, not return opening sizing.
Reference: IRC 2015 Section M1602.2
Your first score is just a starting point. After every attempt, the results page shows how you did on each outline topic, so you can see what to work on next. Compare your score with the real exam's passing score, a minimum score of 70, and keep at it until you pass consistently.
- Start with the questions you know. Go through the whole exam once and bookmark anything you're unsure about. Our practice exams let you bookmark and come back.
- Circle back to your bookmarks on the second pass.
- Keep an eye on your pace. The real exam works out to about 2 minutes 34 seconds per question.
- Turn every miss into a lesson. After each attempt, look up each missed question's reference in your book and read the section.
| Questions | 70 questions |
| Time limit | 3 hours |
| Passing score | a minimum score of 70 |
| Books in the exam room | Open book |
| Exam fee | $115 |
- Results for electronically administered examinations are available immediately after the exam is completed.
- You must wait 10 days before retaking a failed exam.
Source: Denver, Colorado Contractor/Trades Examination Information Bulletin, Published June 3, 2026 (page headers read "August 19, 2025"). Check the bulletin before test day: fees and rules can change.