Refs: IMC 303; 202 (definitions).
Plain English:
IMC 202 (definitions):
Appliance = listed/labeled device that conditions air/water/space (furnace, boiler, WH, RTU/HP/mini-split).
Equipment = distribution/support components (ducts, vents/chimneys, dampers, louvers, piping, controls). Fans/pumps = equipment unless the listing says appliance.
303.1-303.2: Locate per IMC and conditions of listing/MI; no classified (hazardous) locations unless listed for that classification.
303.3: Fuel-fired appliances not in (or taking combustion air from) sleeping rooms, bathrooms, toilet rooms, storage closets, surgical rooms.
Exceptions: Direct-vent; solid-fuel per MI; or sealed dedicated enclosure taking all outdoor air with a solid, weather-stripped, self-closing door (IECC).
303.4-303.7: Provide impact barriers; closet/alcove only if listed; outdoor only if outdoor-listed; pits: >=3 in above floor, >=12 in side clearance, line + 4 in curb if >12 in below grade, 30 in control-side clearance, flood protection.
[BF] 303.8: No mechanical in elevator shafts.
303.9: Group I-2 Condition 2 per IMC 901.4.
On Plans: Why It Matters
Get the type right (appliance vs equipment). The location rules and listings flow from that.
Proof chain: Type -> Code allowance -> Listing/label (if appliance) -> MI page(s).
🧾 Where To Show It (sheet map)
M-001: Definitions note (Appliance vs Equipment). "Locations per IMC 303 and listing/MI; no fuel-fired appliances in prohibited rooms except direct-vent or sealed enclosure; no mechanical in elevator shafts."
M-101/...: Tag by type/function (e.g., RTU-1 appliance; WH-1 appliance; SD-1 smoke damper equipment; OA LOUVER-1 equipment). Call out barriers, any sealed enclosure + OA path, and pit data.
M-501/502: Typical closet/enclosure, barrier/bollard, and pit details.
M-601:
Appliance schedule: model, listing/label, fuel, closet/outdoor suitability, combustion-air source, MI refs.
Equipment schedule: service/performance + product standard (e.g., UL 555/555S for dampers).
Code Path: Equipment Location on Floor Plans
Each piece of fuel-burning mechanical equipment must be shown on the floor plan with the room name, occupancy classification, and a note confirming it is not in a sleeping room, bathroom, toilet room, or storage closet.
M-001 must state that fuel-burning equipment is prohibited from sleeping rooms and bathrooms per IMC 303.3 - this note prevents field substitution of a closet for a mechanical room.
Equipment installed in a mechanical room must show minimum access clearance dimensions on the plan.
Check: Location Verification
Confirm no fuel-burning appliance is shown in or adjacent to a sleeping room, bathroom, toilet room, or storage closet - verify against the architectural room designations.
Verify each equipment room on the plan is labeled as a mechanical room, not a storage or utility closet - labeling affects the applicable installation and access requirements.
For equipment in attics or crawl spaces, confirm the access hatch and working platform are shown per IMC 306.
Review Risk:
Equipment location violations are discovered during inspection when the field installs equipment in a prohibited location that was not on the approved plan - flag the location explicitly on the drawings.
Relocating fuel-burning equipment into a prohibited or unapproved space can require redesign, revised permit documents, and field correction.
Unlabeled mechanical rooms that appear as storage closets on the architectural drawings are a common plan coordination gap.
Field Tip:
Label precisely:
Appliances -> RTU-1, WH-1, HP-1; show listing for the location (closet/outdoor/hazard) and MI page.
Equipment -> SD-1, OA LOUVER-1, EF-1, P-1; cite the applicable product standard-don't apply appliance rules.
If a fuel-fired appliance must be near a bedroom/bath, use direct-vent or a sealed enclosure with outdoor air and an IECC-compliant door.
Match the listing and manufacturer conditions to the proposed location and document the proof path on the coordinated drawings, schedule, or approved submittal.
Masterbuild QA Lens
Prohibited location violations are caught in the first 60 seconds of plan review. Before submitting, confirm: no fuel-fired appliances drawing combustion air from sleeping rooms or bathrooms; appliances in closets/alcoves are listed for that application; outdoor appliances are outdoor-listed. Put the listing basis and prohibited-location compliance note on the equipment schedule, not just the spec.
Drawing / Submittal Check
For IMC 303 (equipment and appliance location): the drawings must confirm each piece of mechanical equipment is not installed in a prohibited location - sleeping rooms, bathrooms, toilet rooms, or storage closets. Show each equipment location on the plan with the room name and occupancy noted. For fuel-burning equipment, confirm the clearances from air openings, ignition sources, and hazardous materials are dimensioned on the plan or detail.
Common Review Risk
The approved location changes in the field because of structural, architectural, or access conflicts. Recheck prohibited-location rules, listing conditions, combustion-air path, damage protection, drainage, service access, and permit-revision requirements before relocation.
When To Escalate
Escalate when the only available equipment location is a prohibited space - when the building configuration places the mechanical room adjacent to a sleeping room or below a bathroom, and the project cannot be redesigned to relocate the equipment. These situations require an AHJ determination of what alternative installation meets the intent of IMC 303.
Rated Assembly Coordination
Equipment location rules affect where mechanical units can be placed relative to fire-rated separations and occupancy boundaries. Mechanical rooms sharing a wall with an adjacent occupancy need the rated assembly confirmed on both the mechanical and architectural drawings.
Load Assumption Check
Equipment location affects load distribution on floors, roofs, and slabs. Confirm that the equipment placement shown on the drawings matches the structural loading assumptions and that no equipment has been relocated since the structural model was run.