International Mechanical Code (IMC): Chapter Map, Editions & Mechanical Inspector Exams
The IMC is not an exam; it is the book that HVAC and mechanical inspector exams are written from. Here is what it covers, which edition applies where, how it differs from the UMC, its 15 chapters, the ICC M2 exam built on it, and four code-lookup questions from our video.
The International Mechanical Code is the International Code Council's model code for heating, cooling, ventilation, exhaust, ducts, combustion air, chimneys and vents, boilers, refrigeration and hydronic piping. The current edition is 2024, but jurisdictions enforce the edition they adopted. ICC's M2 Commercial Mechanical Inspector exam is written from it: 50 open-book questions in 2 hours, a scaled passing score of 75, and a $320 fee.
International Mechanical Code facts at a glance
| Current edition | 2024 IMC: new editions every 3 years; adds A2L/B2L refrigerant identification and a roof-hatch landing |
|---|---|
| Adoption | 46 states + DC: plus Guam, Puerto Rico and the US Virgin Islands; the enforced edition varies |
| Chapters | 15: plus appendices |
| M2 exam | 50 Qs · 2 hours: ICC Commercial Mechanical Inspector, open book |
| M2 passing score | 75 (scaled): ICC's national certification standard |
| M2 / M1 fee | $320 each: national exams; purchases valid 365 days |
| M1 exam | 60 Qs · 2 hours: ICC Residential Mechanical Inspector |
| Exam editions | 2021 and 2024: ICC offers M1 and M2 in both code cycles |
Checked against the official ICC page and the sources listed at the end of this page on 2026-10-26.
Watch: International Mechanical Code video
International Mechanical Code (IMC) Explained: What's on the HVAC & Mechanical Inspector Exams
The IMC chapter map (2024 edition)
Chapters 1 to 3 apply to nearly every installation, so learn them first. Gas piping, gas appliances and their venting are covered by the International Fuel Gas Code instead.
| Chapter | Title |
|---|---|
| 1 | Scope and Administration |
| 2 | Definitions |
| 3 | General Regulations |
| 4 | Ventilation |
| 5 | Exhaust Systems |
| 6 | Duct Systems |
| 7 | Combustion Air |
| 8 | Chimneys and Vents |
| 9 | Specific Appliances, Fireplaces and Solid Fuel-Burning Equipment |
| 10 | Boilers, Water Heaters and Pressure Vessels |
| 11 | Refrigeration |
| 12 | Hydronic Piping |
| 13 | Fuel Oil Piping and Storage |
| 14 | Solar Thermal Systems |
| 15 | Referenced Standards |
Source: ICC: 2024 IMC Code and Commentary, table of contents (PDF)
ICC M2 Commercial Mechanical Inspector content outline
The M2 inspector inspects mechanical systems regulated by the IMC. ICC weights its exam across seven areas.
| Content area | Share of exam |
|---|---|
| Exhaust and Ventilation Systems | 20% |
| General Administration | 15% |
| Heating/Cooling/Water Heaters | 15% |
| Combustion Air | 14% |
| Chimneys and Vents | 14% |
| Duct Systems | 12% |
| Fuel Supply Systems | 10% |
Source: ICC: M2 Commercial Mechanical Inspector content outline (PDF)
What the IMC covers
The IMC sets minimum rules for mechanical systems that are permanently installed to control the environment inside buildings: heating and cooling equipment, ventilation, exhaust, ducts, combustion air, chimneys and vents, boilers and water heaters, refrigeration, hydronic piping, fuel oil, and solar thermal systems.
Two boundaries come up on exams. Fuel gas piping, gas appliances and their venting belong to the International Fuel Gas Code (IFGC). And detached one- and two-family homes and townhouses may follow the International Residential Code instead, which has its own mechanical (M) and fuel gas (G) chapters, depending on what the jurisdiction adopted.
Editions and adoption: which IMC applies?
The current edition is the 2024 IMC, and ICC publishes a new edition every three years. ICC says the IMC is in use or adopted in 46 states, the District of Columbia, Guam, Puerto Rico and the US Virgin Islands, but each state or city enforces the edition it adopted. Texas, for example, adopted the 2024 IMC, IFGC and IRC effective September 1, 2026.
ICC's national M1 and M2 exams are offered in both the 2021 and 2024 code cycles; you choose when you buy the exam. Always match the edition on your exam purchase or your state board's bulletin. North Carolina's heating exams, for example, still use the 2018 North Carolina Mechanical and Fuel Gas Codes.
IMC vs. UMC
The Uniform Mechanical Code (UMC) is a different model code, published by IAPMO. It covers the same subject with different numbering and wording, so never study one for an exam that names the other.
California builds its mechanical code on the UMC: the 2025 California Mechanical Code, part of the California Building Standards Code that took effect January 1, 2026, is based on the 2024 UMC. Texas's licensing department also adopted the 2024 UMC for its air conditioning and refrigeration contractor program, and its candidate bulletin lists the 2024 IFGC, IMC and UMC from September 1, 2026.
Open-book habits for IMC exams
ICC inspector exams are open book, with ICC's rules: bound references, notes in ink or highlighting, and permanently attached tabs. Some state boards are stricter: North Carolina allows highlighting only, no notes, and only commercially available non-removable tabs.
Tab the chapter starts and the tables you keep using, learn the table of contents well enough to jump to a chapter without searching, and check Chapter 2 definitions when a question turns on one word. Many answers sit in Chapter 3, General Regulations.
Four IMC code-lookup questions
These are the original sample questions from our IMC video, written against the 2021 International Mechanical Code. Check the edition your exam uses. They are not from a real ICC exam.
A single air handler's condensate drain is being installed. What is the minimum condensate drain pipe size under Section 307.2.2?
- ½ inch
- ¾ inch
- 1 inch
- 1¼ inches
Show answer
B. ¾ inch
The drain must be at least ¾ inch and may not decrease in size toward the point of disposal. Section 307.2.1 also requires a slope of at least ⅛ unit vertical in 12 units horizontal.
A furnace is installed in an attic. Under Section 306.3, what is the maximum length of the passageway from the opening to the appliance, measured along its centerline?
- 10 feet
- 15 feet
- 20 feet
- 25 feet
Show answer
C. 20 feet
The passageway can be no more than 20 feet long, at least 30 inches high and 22 inches wide, with solid flooring at least 24 inches wide.
Under Section 501.3.1, a bathroom exhaust fan discharges outdoors. How far must the termination be from a mechanical air intake?
- 10 feet
- 3 feet
- 5 feet
- 20 feet
Show answer
A. 10 feet
For environmental air exhaust, the code requires 10 feet from mechanical air intakes. It also requires 3 feet from property lines.
A clothes dryer exhaust duct is being installed in a house. Under Section 504.9.4.1, what is the maximum length of the duct before fittings are deducted?
- 20 feet
- 25 feet
- 30 feet
- 35 feet
Show answer
D. 35 feet
The maximum is 35 feet from the transition duct to the outlet, reduced for each fitting by the equivalent lengths in Table 504.9.4.1. Check the edition your jurisdiction adopted.
International Mechanical Code FAQ
What is the International Mechanical Code?
The ICC's model code for mechanical systems in buildings: heating and cooling, ventilation, exhaust, ducts, combustion air, chimneys and vents, boilers, refrigeration and hydronic piping. States and cities adopt it, sometimes with amendments.
What is the current edition of the IMC?
The 2024 edition. ICC updates the code every three years, but the edition enforced where you work depends on what your state or city adopted.
What is the difference between the IMC and the UMC?
The IMC is published by the International Code Council; the Uniform Mechanical Code is published by IAPMO. They cover similar subjects with different numbering and wording. California's mechanical code, for example, is based on the UMC.
Which ICC exams use the IMC?
The M2 Commercial Mechanical Inspector exam inspects systems regulated by the IMC: 50 open-book questions in 2 hours, $320. The M1 is the Residential Mechanical Inspector exam (60 questions, 2 hours, $320).
Is the M2 exam open book?
Yes. ICC's inspector exams are open book, with rules for bound references, ink or highlighted notes, and permanently attached tabs.
Related practice and guides
Sources
Exam facts on this page were checked against these official pages on 2026-10-26.
- ICC: International Mechanical Code (adoption)
- ICC Store: 2024 International Mechanical Code
- ICC: 2024 IMC Code and Commentary, table of contents (PDF)
- ICC: M2 Commercial Mechanical Inspector content outline (PDF)
- ICC Store: M2 - Commercial Mechanical Inspector
- ICC Store: M1 - Residential Mechanical Inspector
- ICC: Current Certification Exams - National (PDF)
- ICC Support: What score do I need to pass?
- ICC: Texas adopts 2024 International Codes
- IAPMO: Texas adopts 2024 Uniform Mechanical Code
- California DGS Building Standards Commission: Codes
- ICC Store: 2025 California Mechanical Code, Title 24 Part 4
- NC Board: Book reference list (PDF)
OpenExamHub is an independent study resource and is not affiliated with the International Code Council or IAPMO. International Mechanical Code and ICC are trademarks of the International Code Council. The sample questions are original, not from a real exam. Code editions, exam formats, and fees can change; confirm them with ICC and your jurisdiction before you study.