General Administration and Requirements
10%of exam
Heating, Cooling and Water Heaters
24%of exam
Exhaust and Ventilation Systems
8%of exam
Duct Systems
8%of exam
Combustion Air
16%of exam
Chimneys and Vents
19%of exam
Fuel Supply Systems
15%of exam
Quick Facts
- Exam
- ICC M1 Residential Mechanical Inspector
- Edition
- 2024 IRC option
- Questions
- 60 multiple-choice
- Time
- 2 hours
- Reference
- Open book; 2024 IRC
- Pass
- 75 scaled score
- Scoring
- Raw passing count varies by form
- Largest area
- Heating/cooling/water heaters: 24%
- Fuel scope
- Gas and oil systems
Code Lookup
LOCATE: location, occupancy, code, appliance, table, exception
LocationOccupancyCode editionAppliance listingTable notesExceptions
Scaled 75 vs Raw Percent
Scaled 75
- ICC certification passing standard
- Comparable across forms
- Reported as pass/fail
Raw percent
- Questions correct divided by total
- Form-specific threshold
- Not fixed at 45/60
75 is not 75%
2024 IRC Section Picker
- Equipment listing or access→Open M1302–M1307(Then appliance chapter)
- Cooling condensate→Open M1411(Check location and disposal)
- Dryer or cooking exhaust→Open M1502 or M1503(Then M1504 termination)
- Air distribution or returns→Open M1601–M1602(Check exceptions)
- Gas piping or combustion→Open G2407/G2413(Chapter 24)
- Oil storage or piping→Open Chapter 22(Fuel-oil scope)
Inspection Route
- Chapter 1
- Administrative adoption and permits
- M1201
- Mechanical administration scope
- M1302
- Appliance approval and listing
- M1305
- Service and replacement access
- M1306
- Combustible-clearance conditions
- M1307
- Listing and installation instructions
- Inspection order
- Identify system before section lookup
- Local amendment
- Check adopted jurisdiction text
Equipment Installation
- M1401
- Heating/cooling installation
- Equipment listing
- Match intended use and location
- Manufacturer instructions
- Apply alongside IRC requirements
- Service clearance
- Keep required access available
- Garage appliance
- Check M1307 garage protections
- M1411
- Cooling condensate provisions
- Condensate route
- Drain per applicable section
- Safety control
- Verify installed required device
Heating and Cooling
- Furnace
- Check support, access, venting
- Heat pump
- Check listed installation conditions
- Cooling coil
- Check condensate management
- Hydronic system
- Navigate Chapter 21 piping
- Solar thermal
- Navigate Chapter 23
- Fuel-fired appliance
- Check air and vent paths
- Electric appliance
- Check applicable electrical provisions
Boilers and Water Heaters
- M2001
- Boiler installation requirements
- M2002
- Boiler controls and safety
- M2003
- Expansion tank provisions
- M2005
- Water-heater installation
- Potable connection
- Check Chapter 28 interface
- Fuel connection
- Check Chapter 24 if gas
- Relief protection
- Verify applicable discharge path
Local vs Whole-House Ventilation
Local exhaust
- Bathroom/kitchen source
- M1505.5 minimum rate
- Discharge rules apply
Whole-house
- Dwelling outdoor-air rate
- M1505.4.3 area/bedrooms
- Controls and runtime
One can serve both conditionally
Ventilation Decision
- Bathroom local exhaust→Use M1505.5(50 intermittent; 20 continuous cfm)
- Kitchen local exhaust→Use M1505.5(100 intermittent; 25 continuous cfm)
- Whole-dwelling ventilation→Use M1505.4.3(Area/bedrooms and runtime)
- Non-direct, non-mechanical-draft fuel appliance→Check >400cfm exhaust makeup(Inside dwelling air barrier; M1503.6)
- Exhaust termination near intake→Use M1504.3(Check listed exceptions)
Ventilation Rates
- M1505.5 bathroom
- 50 intermittent; 20 continuous cfm
- M1505.5 kitchen
- 100 intermittent; 25 continuous cfm
- Bath fan rating
- Check required static-pressure basis
- M1505.4.3
- Whole-house area/bedroom rate table
- Intermittent whole-house
- ≥25% each 4h; apply factor
- M1505.4.2
- Manual override control
- M1503.6
- Makeup air; qualifying trigger only
Supply vs Return Plenum
Supply plenum
- Delivers conditioned air
- Building cavities barred
- Check M1601.1.1
Return plenum
- Collects return air
- Some cavities conditional
- Check sealing and exclusions
Cavity permission differs
Duct Check
- M1601.1
- Design and approved installation method
- UL 181 ducts
- Listed factory-made ducts
- Joint closure
- Manufacturer-approved sealing system
- M1601.4.2
- Metal lap follows airflow
- M1601.5
- New underfloor plenums prohibited
- Existing underfloor
- Check repair-specific conditions
- Garage HVAC
- No shared dwelling supply/return
- M1602.2
- Return openings; check exceptions
Combustion Air
AIR: appliance, intake, restrictions
Appliance inputsIntake methodRestrictions and interlocks
Indoor vs Outdoor Combustion Air
Indoor path
- Available room volume
- Infiltration condition
- G2407 calculations
Outdoor path
- Opening method
- Net free area
- Louver effects
Choose method before sizing
Air and Vent Decision
- Fuel-gas appliance installed→Check G2407 air(Select authorized method)
- Indoor-air method chosen→Verify volume and infiltration(Use correct calculation)
- Outdoor opening chosen→Size net free area(Account for louver)
- Motorized combustion-air opening→Provide required interlock(Appliance cannot run closed)
- Direct-vent appliance→Follow listed vent assembly(Use manufacturer termination)
Combustion-Air Path
- G2407
- Fuel-gas combustion-air methods
- Indoor air
- Check volume and infiltration
- Outdoor air
- Select compliant opening method
- Appliance input
- Sum relevant fuel loads
- Net free area
- Account for grille/louver rating
- Motorized louver
- Interlock appliance operation
- Blocked opening
- No assumed available airflow
- Mechanical ventilation
- Check interaction with combustion
Venting Path
VENT: verify appliance, exhaust category, notes, termination
Appliance typeVent categoryListing notesTermination
Type B vs Direct Vent
Type B
- Listed gas vent
- Eligible appliances only
- Check clearance/termination
Direct vent
- Listed appliance assembly
- Dedicated air and exhaust
- Follow manufacturer termination
Listing governs selection
Chimney and Vent Check
- R1003
- Masonry chimney construction
- R1005
- Factory-built chimney listing
- M1801
- Venting general requirements
- Liner
- Match fuel and appliance
- Unused opening
- Close or cap
- Vent support
- Carry system weight
- Duct/plenum
- No vent penetration through air path
- Direct vent
- Follow appliance listing and instructions
Masonry vs Factory-Built Chimney
Masonry
- R1003 construction
- Compatible lining
- Clearance by location
Factory-built
- R1005 installation
- Listed assembly
- Manufacturer clearances
Construction rules differ
Vent Selection
- G2427
- Fuel-gas venting path
- G2428
- Vent-sizing provisions
- Category I
- Check listed vent sizing
- Category IV
- Use listed pressure-tight vent system
- Type B
- Check appliance and vent listing
- Single-wall
- Check location and clearance limits
- Connector
- Material and routing conditions
- Termination
- Check type-specific location rules
- Common vent
- Check eligible appliance combinations
Gas Sizing Memory
GASP: gas, assumptions, section, path
Gas heating valueAssumed pressure/drop/SGSection demandPath length
Gas vs Fuel-Oil Supply
Fuel gas
- Chapter 24
- Pipe sizing and pressure
- G2413/G2417
Fuel oil
- Chapter 22
- Tank and piping
- M2201/M2202
Navigate fuel-specific chapter
Gas Pipe Table Picker
- Connected appliances listed→Total section Btuh(Include downstream loads)
- Heating value known→Convert Btuh to CFH(Use actual gas value)
- Sizing method selected→Determine applicable path length(G2413.4 method)
- Schedule 40 natural gas→Check G2413.4(1)(SG .60; <2psi; .5in drop)
- Conditions differ from table→Select matching table/method(Never transfer capacity blindly)
- Installed gas pipe→Check G2417 test(Before acceptance)
Gas Table Inputs
- G2413
- Gas pipe sizing framework
- Load conversion
- Btuh divided by gas heating value
- Section demand
- Sum connected downstream input
- G2413.4(1)
- Schedule 40 metallic gas table
- Table gas
- Natural gas; SG 0.60
- Table pressure
- Inlet below 2 psi
- Table drop
- 0.5 inch water column
- Table length
- Use selected method/path length
- Capacity
- Match diameter to required CFH
- Different conditions
- Choose corresponding table or method
Gas and Oil Controls
- G2417
- Gas pressure-test provisions
- G2420
- Accessible appliance shutoffs
- G2422
- Appliance connection provisions
- Unused gas outlet
- Cap or plug safely
- Material transition
- Use listed compatible fittings
- M2201
- Fuel-oil tank installations
- M2202
- Fuel-oil piping provisions
- Oil fill/vent
- Check Chapter 22 conditions
Common Traps
Score interpretation
75 scaled score ≠ 75% raw correctness
Edition choice
2024 IRC option ≠ Older IRC section text
Local versus whole
M1505.5 local exhaust ≠ M1505.4.3 whole-house rate
Makeup-air trigger
Qualifying appliance plus >400cfm exhaust ≠ Every large hood unconditionally
Garage air path
Shared dwelling HVAC prohibited ≠ Dedicated garage system conditional
Category IV vent
Listed pressure-tight vent assembly ≠ Generic PVC assumption
Gas table transfer
Match length, pressure, SG, material ≠ Reuse unrelated table capacity
Venting exception
Check appliance listing and exception ≠ Assume universal termination distance
Last Minute
- 1.M1: 60MCQ; 2h; open-book
- 2.Pass: 75 scaled, not 45/60
- 3.Administration: 10%; equipment: 24%
- 4.Exhaust: 8%; ducts: 8%
- 5.Combustion air: 16%; vents: 19%
- 6.Fuel supply: 15%
- 7.Match 2024 IRC exam edition
- 8.M1307: listing and installation instructions
- 9.M1411: cooling condensate conditions
- 10.Bathroom: 50cfm intermittent; 20cfm continuous
- 11.M1505.4.3: whole-house area/bedrooms
- 12.M1602.2: return-air exceptions matter
- 13.G2407: choose combustion-air method first
- 14.G2427: appliance-specific vent route
- 15.G2413.4: match every table assumption
- 16.G2417: pressure-test requirements
- 17.Chapter 22 covers fuel oil
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