About this chapter: Chapter 3 addresses many unrelated topics that would be out of place in other chapters that address specific subjects. Topics include listing and labeling, structural safety, appliance locations, access, combustion air, installation requirements, clearances, electrical bonding and condensate disposal.
For structures located in flood hazard areas, the appliance, equipment and system installations regulated by this code shall be located at or above the elevation required by Section 1612 of the International Building Code for utilities and attendant equipment.
Exception: The appliance, equipment and system installations regulated by this code are permitted to be located below the elevation required by Section 1612 of the International Building Code for utilities and attendant equipment provided that they are designed and installed to prevent water from entering or accumulating within the components and to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to such elevation.
- The appliance is a direct-vent appliance installed in accordance with the conditions of the listing and the manufacturer's instructions.
- Vented room heaters, wall furnaces, vented decorative appliances, vented gas fireplaces, vented gas fireplace heaters and decorative appliances for installation in vented solid fuel-burning fireplaces are installed in rooms that meet the required volume criteria of Section 304.5.
- The appliance is installed in a room or space that opens only into a bedroom or bathroom, and such room or space is used for no other purpose and is provided with a solid weather-stripped door equipped with an approved self-closing device. Combustion air shall be taken directly from the outdoors in accordance with Section 304.6.
- A clothes dryer is installed in a residential bathroom or toilet room having a permanent opening with an area of not less than 100 square inches (0.06 m2) that communicates with a space outside of a sleeping room, bathroom, toilet room or storage closet.
303.3.1 Fireplaces and Decorative Appliances in Group I-1, Condition 2 and Group I-2, Condition 2 Occupancies
- The direct-vent gas fireplaces are not located within a sleeping room.
- The direct-vent fireplaces have a sealed glass front with a wire mesh panel or screen.
- The controls for the direct-vent gas fireplace are located where they can be accessed only by facility staff.
- Electrically supervised carbon monoxide detection is provided in the room where the direct-vent gas fireplace is located.
- The direct-vent fireplace includes a guard in front of the glass where the glass temperature is equal to or exceeds 125°F (52°C).
- Type 1 clothes dryers that are provided with makeup air in accordance with the manufacturer's installation instructions.
- Combustion air for power burner appliances equipped with a draft control device and having an input above 400,000 Btu/hr shall have a net free area of 0.2 square inches per 1,000 Btu/hr. Combustion air shall be provided from a single opening from the outdoors. In lieu of this requirement, combustion air requirements specified by the manufacturer for a specific power burner appliance may be approved by the building official.
- Combustion air for power burner appliances not equipped with a draft control device and having an input above 400,000 Btu/hr shall have a net free area of 0.1 square inches per 1,000 Btu/hr. Combustion air shall be provided from a single opening from the outdoors. In lieu of this requirement, combustion air requirements specified by the manufacturer for a specific power burner appliance may be approved by the building official.
- Combustion air for Category I, III, and IV gas-fired appliances shall be determined using Table 304.1.
- Combustion air requirements for residential dwellings shall be calculated by using Worksheet E-1, "Residential Combustion Air Calculation Method" and Table E-1, "Residential Combustion Air Required Volume" located in IFGC Appendix E, as amended in Minnesota Rules, parts 1346.6012 and 1346.6014.
|Total input of appliances1
thousands of Btu/hr (kW)
|Required free area of
air-supply opening or duct,
square inches (sq mm)
round duct equivalent
diameter2, inch (mm)
|25 (8)||7 (4,500)||3 (75)|
|50 (15)||7 (4,500)||3 (75)|
|75 (23)||11 (7,000)||4 (100)|
|100 (30)||14 (9,000)||4 (100)|
|125 (37)||18 (12,000)||5 (125)|
|150 (45)||22 (14,000)||5 (125)|
|175 (53)||25 (16,000)||6 (150)|
|200 (60)||29 (19,000)||6 (150)|
|225 (68)||32 (21,000)||6 (150)|
|250 (75)||36 (23,000)||7 (175)|
|275 (83)||40 (26,000)||7 (175)|
|300 (90)||43 (28,000)||7 (175)|
|325 (98)||47 (30,000)||8 (200)|
|350 (105)||50 (32,000)||8 (200)|
|375 (113)||54 (35,000)||8 (200)|
|400 (120)||58 (37,000)||9 (225)|
1 For total inputs falling between listed capacities, use next largest listed input.
2 If flexible duct is used, increase the duct diameter by one inch.*
* Flexible duct shall be stretched with minimal sags.
Where the air infiltration rate of a structure is known, the minimum required volume shall be determined as follows:
For appliances other than fan-assisted, calculate volume using Equation 3-1.
For fan-assisted appliances, calculate volume using Equation 3-2.
For purposes of this calculation, an infiltration rate greater than 0.60 ACH shall not be used in Equations 3-1 and 3-2.
The outdoor opening(s) size shall be calculated in accordance with the following:
- The ratio of interior spaces shall be the available volume of all communicating spaces divided by the required volume.
- The outdoor size reduction factor shall be one minus the ratio of interior spaces.
- The minimum size of outdoor opening(s) shall be the full size of outdoor opening(s) calculated in accordance with Section 304.6, multiplied by the reduction factor. The minimum dimension of air openings shall be not less than 3 inches (76 mm).
- Ducts shall be of galvanized steel or an equivalent corrosion-resistant material. If flexible duct is used, increase the duct diameter by one inch. Flexible duct shall be stretched with minimal sags.
- Ducts shall terminate in an unobstructed space, allowing free movement of combustion air to the appliances.
- Ducts shall serve a single space.
- Ducts shall not service both upper and lower combustion air openings where both such openings are used. The separation between ducts serving upper and lower combustion air openings shall be maintained to the source of combustion air.
- Ducts shall not terminate in an attic space.
- The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry, metal or factory-built chimney shall not be used to supply combustion air.
- Vertical ducts shall not extend through two or more stories without prior approval from the building official.
- Ducts shall not terminate in the return air plenum of a forced air heating system unless installed in accordance with the heating equipment manufacturer's installation instructions.
- Combustion air intake openings shall be located to avoid intake of exhaust air in accordance with IMC Section 401.5 and IFGC Section 503.8 and shall be covered with corrosion resistant screen of not less than 1/4 inch (6.4 mm) mesh.
- Combustion air intake openings shall be located at least 12 inches (305 mm) above adjoining grade level.
- When both makeup air and combustion air openings are required, they shall be provided through separate openings to the outdoors.
Where corrosive or flammable process fumes or gases, other than products of combustion, are present, means for the disposal of such fumes or gases shall be provided. Such fumes or gases include carbon monoxide, hydrogen sulfide, ammonia, chlorine and halogenated hydrocarbons.
In barbershops, beauty shops and other facilities where chemicals that generate corrosive or flammable products, such as aerosol sprays, are routinely used, nondirect vent-type appliances shall be located in a mechanical room separated or partitioned off from other areas with provisions for combustion air and dilution air from the outdoors. Direct-vent appliances shall be installed in accordance with the appliance manufacturer's instructions.
Equipment and appliances shall be installed as required by the terms of their approval, in accordance with the conditions of listing, the manufacturer's instructions and this code. Manufacturers' installation instructions shall be available on the job site at the time of inspection. Where a code provision is less restrictive than the conditions of the listing of the equipment or appliance or the manufacturer's installation instructions, the conditions of the listing and the manufacturer's installation instructions shall apply.
Unlisted appliances approved in accordance with Section 301.3 shall be limited to uses recommended by the manufacturer and shall be installed in accordance with the manufacturer's instructions, the provisions of this code and the requirements determined by the code official.
Equipment and appliances having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor in hazardous locations and public garages, private garages, repair garages, motor fuel-dispensing facilities and parking garages. For the purpose of this section, rooms or spaces that are not part of the living space of a dwelling unit and that communicate directly with a private garage through openings shall be considered to be part of the private garage.
Connection of a parking garage with any room in which there is a fuel-fired appliance shall be by means of a vestibule providing a two-doorway separation, except that a single door is permitted where the sources of ignition in the appliance are elevated in accordance with Section 305.3.
Appliances located in public garages, motor fuel-dispensing facilities, repair garages or other areas frequented by motor vehicles shall be installed not less than 8 feet (2438 mm) above the floor. Where motor vehicles are capable of passing under an appliance, the appliance shall be installed at the clearances required by the appliance manufacturer and not less than 1 foot (305 mm) higher than the tallest vehicle garage door opening.
Exception: The requirements of this section shall not apply where the appliances are protected from motor vehicle impact and installed in accordance with Section 305.3 and NFPA 30A.
Rooms containing appliances shall be provided with a door and an unobstructed passageway measuring not less than 36 inches (914 mm) wide and 80 inches (2032 mm) high.
Exception: Within a dwelling unit, appliances installed in a compartment, alcove, basement or similar space shall be provided with access by an opening or door and an unobstructed passageway measuring not less than 24 inches (610 mm) wide and large enough to allow removal of the largest appliance in the space, provided that a level service space of not less than 30 inches (762 mm) deep and the height of the appliance, but not less than 30 inches (762 mm), is present at the front or service side of the appliance with the door open.
Attics containing appliances shall be provided with an opening and unobstructed passageway large enough to allow removal of the largest appliance. The passageway shall be not less than 30 inches (762 mm) high and 22 inches (559 mm) wide and not more than 20 feet (6096 mm) in length measured along the centerline of the passageway from the opening to the appliance. The passageway shall have continuous solid flooring not less than 24 inches (610 mm) wide. A level service space not less than 30 inches (762 mm) deep and 30 inches (762 mm) wide shall be present at the front or service side of the appliance. The clear access opening dimensions shall be not less than 20 inches by 30 inches (508 mm by 762 mm) and large enough to allow removal of the largest appliance.
- The passageway and level service space are not required where the appliance is capable of being serviced and removed through the required opening.
- Where the passageway is not less than 6 feet (1829 mm) high for its entire length, the passageway shall be not greater than 50 feet (15 250 mm) in length.
Under-floor spaces containing appliances shall be provided with an access opening and unobstructed passageway large enough to remove the largest appliance. The passageway shall be not less than 30 inches (762 mm) high and 22 inches (559 mm) wide, nor more than 20 feet (6096 mm) in length measured along the centerline of the passageway from the opening to the appliance. A level service space not less than 30 inches (762 mm) deep and 30 inches (762 mm) wide shall be present at the front or service side of the appliance. If the depth of the passageway or the service space exceeds 12 inches (305 mm) below the adjoining grade, the walls of the passageway shall be lined with concrete or masonry extending 4 inches (102 mm) above the adjoining grade and having sufficient lateral-bearing capacity to resist collapse. The clear access opening dimensions shall be not less than 22 inches by 30 inches (559 mm by 762 mm), and large enough to allow removal of the largest appliance.
- The passageway is not required where the level service space is present when the access is open and the appliance is capable of being serviced and removed through the required opening.
- Where the passageway is not less than 6 feet high (1829 mm) for its entire length, the passageway shall not be limited in length.
The permanent stair shall be as required by relevant safety regulations, but shall not be less than the following:
- The stair shall be installed at an angle of not more than 60 degrees measured from the horizontal plane.
- The stair shall have flat treads at least 6 inches (152 mm) deep and a clear width of at least 18 inches (457 mm) with equally spaced risers at least 10.5 inches (267 mm) high and not exceeding 14 inches (356 mm).
- The stair shall have intermediate landings not exceeding 18 feet (5.5 m) vertically.
- Continuous handrails shall be installed on both sides of the stair.
- Interior stairs shall terminate at the under side of the roof at a hatch or scuttle of at least 8 square feet (0.74 m2) with a minimum dimension of 20 inches (508 mm).
- When a roof access hatch or scuttle is located within 10 feet (3.0 m) of a roof edge, a guard shall be installed in accordance with IFGC section 306.6.
- Exterior stairs shall terminate at the roof access point or at a level landing of at least 8 square feet (0.74 m2) with a minimum dimension of 20 inches (508 mm). The landing shall have a guard installed in accordance with IFGC section 306.6.
- Width shall be at least 16 inches (406 mm).
- Rung spacing shall be a maximum of 14 inches (356 mm).
- Toe space shall be at least 6 inches (152 mm).
- Side railings shall extend at least 30 inches (762 mm) above the roof or parapet wall.
Category IV condensing appliances shall be provided with an auxiliary drain pan where damage to any building component will occur as a result of stoppage in the condensate drainage system. Such pan shall be installed in accordance with the applicable provisions of Section 307 of the International Mechanical Code.
The allowable clearance reduction shall be based on one of the methods specified in Table 308.2 or shall utilize a reduced clearance protective assembly listed and labeled in accordance with UL 1618. Where required clearances are not listed in Table 308.2, the reduced clearances shall be determined by linear interpolation between the distances listed in the table. Reduced clearances shall not be derived by extrapolation below the range of the table. The reduction of the required clearances to combustibles for listed and labeled appliances and equipment shall be in accordance with the requirements of this section, except that such clearances shall not be reduced where reduction is specifically prohibited by the terms of the appliance or equipment listing [see Figures 308.2(1) through 308.2(3)].
REDUCTION OF CLEARANCES WITH SPECIFIED FORMS OF PROTECTION a through k
|TYPE OF PROTECTION APPLIED TO |
AND COVERING ALL SURFACES OF COMBUSTIBLE
MATERIAL WITHIN THE DISTANCE SPECIFIED AS THE
REQUIRED CLEARANCE WITH NO PROTECTION
[see Figures 308.2(1), 308.2(2) and 308.2(3)]
|WHERE THE REQUIRED CLEARANCE WITH NO PROTECTION FROM |
APPLIANCE, VENT CONNECTOR OR SINGLE-WALL METAL PIPE IS: (inches)
|Allowable clearances with specified protection (inches)|
|Use Column 1 for clearances above appliance or horizontal connector. Use Column 2 |
for clearances from appliance, vertical connector and single-wall metal pipe.
|1. 31/2-inch-thick masonry wall without ventilated |
|2. 1/2-inch insulation board over 1-inch glass fiber or |
mineral wool batts
|3. 0.024-inch (nominal 24 gage) sheet metal over 1-inch |
glass fiber or mineral wool batts reinforced with wireon rear face with ventilated airspace
|4. 31/2-inch-thick masonry wall with |
|5. 0.024-inch (nominal 24 gage) sheet metal with |
|6. 1/2-inch-thick insulation board with ventilated |
|7. 0.024-inch (nominal 24 gage) sheet metal with |
ventilated airspace over 0.024-inch (nominal 24 gage)sheet metal with ventilated airspace
|8. 1-inch glass fiber or mineral wool batts sandwiched |
between two sheets 0.024-inch (nominal 24 gage)sheet metal with ventilated airspace
For SI: 1 inch = 25.4 mm, °C = [(°F) - 32]/1.8, 1 pound per cubic foot = 16.02 kg/m3, 1 Btu per inch per square foot per hour per °F = 0.144 W/m2 • K.
- Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing.
- Clearances shall be measured from the outer surface of the combustible material to the nearest point on the surface of the appliance, disregarding any intervening protection applied to the combustible material.
- Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite an appliance or connector.
- For all clearance reduction systems using a ventilated airspace, adequate provision for air circulation shall be provided as described [see Figures 308.2(2) and 308.2(3)].
- There shall be not less than 1 inch between clearance reduction systems and combustible walls and ceilings for reduction systems using ventilated airspace.
- Where a wall protector is mounted on a single flat wall away from corners, it shall have a minimum 1-inch air gap. To provide air circulation, the bottom and top edges, or only the side and top edges, or all edges shall be left open.
- Mineral wool batts (blanket or board) shall have a minimum density of 8 pounds per cubic foot and a minimum melting point of 1500°F.
- Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1.0 Btu per inch per square foot per hour per °F or less.
- There shall be not less than 1 inch between the appliance and the protector. In no case shall the clearance between the appliance and the combustible surface be reduced below that allowed in this table.
- Clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable.
- Listed single-wall connectors shall be installed in accordance with the manufacturer's instructions.
- Rooms containing a boiler that is regulated by Minnesota Rules, chapter 5225, shall be provided with carbon monoxide alarms in accordance with that chapter.
- Where the room containing the fuel-burning appliance is located in a building regulated by the International Residential Code, carbon monoxide alarms shall be provided in accordance with Minnesota Rules, chapter 1309.