We're launching IMC Section 304 as a tight three-part series. This is where plan-review friction loves to hide-installing per listing/MI, ignition-source elevation in/near garages, hydrogen provisions, and those easy-to-miss details like grade pads and roof guards.
We'll cover 304 in three focused parts:
Part 1: 304.1-304.4 - Approval/MI on site, resolving code vs. MI conflicts, ignition-source elevation, parking-garage vestibules, and prohibited hazardous areas.
Part 2: 304.5 - Hydrogen generating/refueling: natural vs. mechanical ventilation, opening sizing/placement, engineered alternatives.
Part 3: 304.6-304.12 - Public/private garage mounting heights & impact protection, boiler/furnace room protection (IBC), clearances to combustibles, clearances from grade/pads, roof guards, and "area served."
Part 1 drops tomorrow.
Code Path: IMC Section 304.1 (Approval/MI on Site) -> Section 304.2 (Code vs. MI Conflicts) -> Section 304.4 (Ignition Source Elevation in Garages) -> Section 304.5 (Hydrogen Generating/Refueling) -> Section 304.6-304.12 (Garage Mounting Heights, Protection, Boiler Rooms). Cross-reference IBC for structural and NFPA 88A for parking garages.
Section 304.4: Appliance ignition sources must be 18 inches above the garage floor - no exceptions for 'low-profile' equipment.
Section 304.5: Hydrogen ventilation requirements must be calculated and shown on the plans - not deferred to the contractor.
Section 304.6-304.7: Impact protection for equipment near vehicle traffic paths must be shown on the floor plan or detail sheet.
Check: Before You Submit
Confirm mounting heights for all equipment in garage applications are shown with dimension callouts on the floor plan.
Verify ignition source elevations (burners, pilots, switches) are at least 18 inches above finished floor in all garage settings.
Confirm hydrogen system ventilation calculations (natural or mechanical) are included in the permit package.
Review Risk:
Equipment in garage applications without the applicable mounting height, ignition-source, impact-protection, and listing basis leaves the installation path incomplete.
Hydrogen ventilation design omitted or deferred to the contractor without a code-compliant basis on the permit set.
Impact protection for equipment near vehicle traffic paths not shown on the floor plan or detail sheet.
Masterbuild QA Lens
Mounting height, clearance, and protection requirements are often left for the contractor to resolve in the field - which is exactly where they create inspection failures and rework. Show mounting heights, service clearances, and impact protection on the mechanical plans before submittal. Field assumptions are not an acceptable substitute for drawn information.
Drawing / Submittal Check
For applicable garage conditions, show the Section 304.3 ignition-source elevation and the Section 304.6 or 304.7 equipment-location/protection path, including exceptions. Show listed/manufacturer combustible clearances and identify equipment serving an area other than its installation location.
Common Review Risk
Field risks include confusing ignition-source elevation with equipment mounting requirements, omitting vehicle-impact protection, or reducing a listed combustible clearance without a valid Section 308 path.
When To Escalate
Escalate when the equipment installation sequence conflicts with the structural framing sequence - when the mechanical equipment must be in place before the structural framing above it is complete, creating a window where the equipment cannot be accessed or protected. Installation sequence conflicts require a coordinated construction schedule agreed upon by all trades before construction starts.
Special Condition-Battery Rooms
For battery rooms or charging areas, confirm the battery type, hazard basis, ventilation calculation, control sequence, alarm interface, exhaust path, and AHJ or fire-protection coordination are all traceable. The drawing set should not leave the safety logic implied.
Special Exhaust Coordination
For specialty exhaust, start with the contaminant and source. Then confirm capture method, duct material, routing, discharge, separation, controls, and whether another consultant or AHJ review is required.