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the space in the crawl space where heating equipment is to be installed
shall be accessible by an opening and passageway at least as large as
that required to install or remove the heating equipment without disas-
sembling such equipment. Liquefied petroleum gas-fired heating appli-
ances shall not be installed in any imderfloor space unless such space is
provided with an approved means for removal of unbumed gas.


M-308.1 Clearance: Flat floor furnaces shall be installed not less than
six (6) inches from walls. Wall register floor furnaces shall be installed
not less than six (6) inches from inside room comers.

Exception: Replacement floor furnaces of the same or lesser input
rating may be installed in the original location as approved by the

M-308.2 Installation


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M-308.2.1 Floor furnaces shall not be located where a door can swing
within twelve (12) inches of the warm air outlet.

M-308.2.2 Floor furnace warm air outlets shall not be installed less
than sixty (60) inches below overhead projections.

M-308.2.3 A clear floor space of twenty-four (24) inches shall be pro*
vided along two (2) adjoining sides of flat floor furnaces.

M-308.2.4 The floor furnace burner assembly shall not project into an
occupied underfloor area.

M''30S.3 Access: An opening and passageway not less than twenty*
four (24) inches by eighteen (18) inches shall be provided to every floor
furnace. The passageway shall be not more than twenty (20) feet in
length from the access opening or from an underfloor area thirty (30)
inches or more in height.

M.30S.4 Setting

M-30S.4.1 Floor furnaces shall be supported independently of the grille
ami shall have not less than six (6) inches clearance from grade. Floor
furnaces shall not be installed on concrete slabs on grade.

Exception: Sealed furnaces may have a grade clearance of two (2)

M-308.4.2 Furnace excavations shall extend not less than thirty (30)
inches beyond the control side and twelve (12) inches beyond the sides
and back of the furnace. The excavation shall slope outward from the
bottom to the natural grade at an angle not greater than forty-five (45)
degrees from the horizontal.


M-309.1 General: Heating and ventilating equipment in occupancies
involving fire hazards from flammable vapors, dust, combustible fibers
or other highly combustible substances shall be installed and protected
against fire and explosion hazards in accordance with nationally recog-
nized safety practice standards and as approved by the department prior
to installation.


M-310.1 Definition: See the building code of this jurisdiction.

M-310.2 Location of heating equipment: Heating equipment to be
installed in service stations shall be located at least five (5) feet six (6)
inches from the floor to the bottom of the unit and at least eight (8) feet
in the lubritory area. Heating equipment shall not be located below


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M-310.3 Clearance: Suspended horizontal furnaces shall be installed
with clearances as shown in Table M-303.

M-310.4 Ducts: Return air and supply air shall be provided to the
furnace through approved ducts. Duct construction shall conform to the
requirements of Table M-301.4 and/ or the standards listed in Appendix B.

M-310.5 Additional requirements: In addition to the requirements of
this section, furnaces installed shall meet the requirements of Article 6.


M-311.1 General: Heaters shall not be installed as a central heating
system unless as otherwise approved by the department.

M-311.1,1 Fuel-burning space heaters shall be equipped with a flame

M-311.1.2 Space heaters shall be installed so as not to cause a fire
hazard to walls, floors, curtains, furniture, open doors, or to the free
movement of persons within the room. See Table M-303.

M-311.1.3 The use of fuel-burning unvented space heaters is prohibited,
except as provided for in Section M-300.13.10.

M-311.2 Through-the-wall heaters

M-311.2.1 Through-the-wall heaters shall not be installed as central
heating except as otherwise approved by the department.

M-31 1.2.2 Combustion air intakes and/ or vents shall be located on the
exterior of the building, and such openings shall be at least twelve (12)
inches above the exterior finished grade. When such heaters are located in
garages or accessory use buildings where motor-driven vehicles or devices
utilizing volatile liquids are housed or stored, combustion air openings
and vents shall be located at least eighteen (18) inches from the exterior
finished grade, and interior pilot light access opening shall be located at
least eighteen (18) inches from the finished floor. Where combustion air
intake openings are located immediately adjacent to a driveway, the
exterior eighteen (18) inch height requirements shall apply. The equip-
ment shall be protected from any type of mechanical injury from ve-
hicular traflBc. Vents from such heaters shall not be located within twelve
(12) inches of any window, door or opening into a building.

M-311.2.3 Clearances: Through-the-wall heaters shall not be installed
within twelve (12) inches from any projecting combustible material
which extends vertically or horizontally from the wall surface. Such
heaters shall not be located within twelve (12) inches of the comer of
the building or any other projection from the wall surface on which
they are installed.

Exception: Through-the-wall heaters may be installed with lesser


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clearances when accepted by a nationally recognized testing or inspec-
tion agency.

M-311.2.4 Prohibited installations: Through-the-wall heaters shall not
extend into any public walkway or public way or private walkway in
such a manner that would constitute a hazard to the public.

M-311.3 Recessed (wall) heaters

M-311.3.1 Recessed heaters shall not be installed as central heating
except as provided for in Section M-300.11.

M-311.3.2 Recessed heaters shall be an approved type and shall be
installed in accordance with the requirements of their listing, the manu-
facturer's instructions and the requirements of this code.

M-31 1.3.3 Panels, grilles or access doors shall be provided to allow
normal servicing operations to recessed heaters.

M-31 1.3.4 Recessed heaters installed in rooms normally kept closed
shall be equipped with a flame safeguard and such rooms shall be pro-
vided with adequate combustion air.


M-312.1 General: Approved vented infrared fuel-fired heating units
may be utilized when installed in accordance with their listing. Unvented
infrared fuel-fired heating units for space heating in industrial occupan-
cies shall be considered vented when die units do not exceed input ratings
of fifty thousand (50,000) Btus per hour per unit and have been approved
for use without directly connected vents and installed in accordance
with the following provisions of this section.

M-312.2 Ordinary occupancy

M-312.2.1 For full building heating by infrared space heaters, the
units shall be mounted with strict adherence to clearances to combusti-
bles as determined by a nationally recognized testing or inspection
agency, and as indicated in the listing and in accordance with the
manufacturer s recommendations. Units for spot heating applications may
be at a lower mounting height than that for full building heating.

M-312.2.2 Natural or mechanical ventilation shall be provided for the
space to be heated. Provision must be made for both outside air supply
and exhaust. Natural ventilation shall consist of suflBcient outlet area
adequately distributed above the units and having a capacity to reduce
the CO2 produced by the units to five thousand (5^000) parts per million
(ppm) of air and to reduce the CO produced to fifty (50) ppm of air (3.8
and 4.55 cfm/ 1,000 Btu/hr for natural and propane respectively). Capacity
shall be determined by the following formula:


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V = 9.4AVH(ti-tb) A = .



V = Volume of air exhausted in cubic feet per minute (cfm)
A = Free area of outlets in square feet
H = Height from inlets to outlets in feet

ti = Average temperature of indoor air in height H in degrees Fahren-
to = Outdoor air temperature in degrees Fahrenheit

Inlet air area shall be fixed and equal in amount to the outlet area as
determined in A above. Infiltration area can be included in the inlet area.
If by virtue of other mechanical exhaust equipment and provided more
than two (2) air changes per hour produces a negative pressure in the
building space, positive mechanical supply of air in equal amount of
excess over two (2) air changes per hour must be provided. This supply
air shall be tempered with inside air or be pre-heated. Mechanical
ventilation systems, where used, shall consist of fans or blowers providing
a positive pressure in the space. Fixed exhaust openings shall be pro-
vided at the high point of the space. Exhaust area shall be equal to two
(2) square feet per one thousand (1,000) cfm introduced. Air provided
must be in an amount suflBcient to reduce CO and CO2 as indicated in the
above and must be tempered with inside air to be preheated. Mechanical
ventilation shall be interlocked with the heaters so that the heaters can-
not operate unless the mechanical ventilation is operating.

M-312.3 Semi-hazardous occupancy (garages and aircraft hangars)

M-312.3.1 Units shall be listed for use in the areas by a nationally
recognized testing or inspection agency and shall be installed and located
in accordance with NFiPA 88 and 409 listed in Appendix B. Sections
M-312.2.1 and M-312.2.2 shall also apply.

M-3I2.3.2 Ventilation shall be of the mechanical type and shall comply
with Section M-317.0 of this article. In addition, the ventilation system
shall be so designed as to maintain a zero or positive pressure in the space
at all times.

M-312.3.3 An auxiliary positive air supply and fixed exhaust openings
in the high point of the space must be provided in order to reduce the
CO2 and CO produced by the heaters to five thousand (5,000) ppm and
one hundred (100) ppm of air respectively, as described above. This
auxiliary system is to be so interlocked with the main ventilation system
that it will operate when the main ventilation system is not operating.
Under this condition, the auxihary system need operate only when heaters
are on.


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M-313.1 Location: In addition to other approved locations, approved
unit heaters may be installed in garages, enclosed loading docks and
similar occupancies. When such heaters are to be installed in public repair
or storage garages and suspended from the ceiling or roof, they shall be at
least eight (8) feet measiured from the floor to the bottom of the unit. In
spaces where vehicular equipment in excess of six (6) feet in height is
present, a minimum of two (2) feet clearance shall be provided between
the bottom of the unit heaters and the top of such equipment.

M-313.1.1 Unit heaters to be installed in private garages and suspended
from the ceiling or roof shall be installed with a clearance of at least
five (5) feet six (6) inches measured from the floor to the bottom of the

M-313.1.2 The location of such heaters to be installed in hazardous
occupancies and airplane hangers shall be approved prior to installation.

M-313.2 Clearance: For clearance to combustible materials, see Table
M-303. Heaters approved for lesser clearance may be installed accord-

M-313.3 Venting: See Article 7.

F-313.4 Supports: Suspended type unit heaters shall be safely and
adequately supported. Hanger brackets and other such supports shall
be of noncombustible material.

M-313.5 Combustion air: See Article 6.

M-313.8 High static duct heaters: When such heaters are used in
conjunction with a duct system, they shall be installed in accordance
with the duct work and clearance requirements of this article.

M-313.7 Low-static unit heaters

M-313.7.1 Ducts shall not be used in conjunction with low-static unit

M-313.7.2 Central warm air heating: See Section M-300.11.


M-314.1 Location: Gravity furnaces shall be located so that the length
of the warm air pipes shall be equalized as nearly as practicable, with
due preference to rooms which have unusual heating requirements.

M-314.2 Separation

M-314.2.1 Where warm air and return air pipes on gravity systems are
six (6) inches or less apart, at least one-half (H) inch of approved insula-
tion shall be installed on the return air pipe.

M-314.2.2 Where the distance between return pipes and vent pipes is

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twelve (12) inches or less in solid or liquid fuel furnaces, or six (6) inches
or less in gas furnaces, such return pipes shall be insulated with at least
one-half (K) inch insulating material or with reflective metal set one (1)
inch out from the pipe.

M-314.3 Material: Warm air pipes shall be constructed entirely of
noncombustible material equivalent to the structural strength and dura-
bility required in Table M-301.4.

M-314.4 Construction: Warm air pipes shall be constructed in the
following manner described in Sections M-314.4.2 through M-314.4.8.

M-314.4.1 Side seams shall be locked seams.

M-314.4.2 Joints shall be either seamed or lapped at least one and
one-half (lit) inches.

M-314.4.3 Pipes and fittings shall be properly secured to ceiling or
joists with metal lugs or straps.

M-314.4.4 Gravity warm air supply runs in basements shall have a
vertical rise of one (1) inch for each horizontal run of one (1) foot. On
extended plenums, or where the total rise is taken at the furnace, the rise
shall be at least one and one-half (Di) inches per linear foot of run.

M-314.4.5 Warm air pipes shall afford a clearance of at least one (1)
inch from any combustibles.

M-314.4«6 Warm air pipes from solid and liquefied fuel gravity fur-
naces shall be at least six (6) inches from combustible material for a
distance of six (6) feet from the furnace plenum.

M-314.4.7 Adhesive coverings for pipes if used, shall be of material
approved for such use.

M-314.4.8 The return air supply to the furnace may be taken from
within the building or may be taken partially from outside and partially
from within. If a proportioning damper is used on such split air supply,
it shall be so arranged that for all possible positions of the damper, the
total open cross-sectional area shall be at least the total cross-sectional
area of all warm air outlets. All joints in the pipe system shall be made

M-314.5 Dampers: Warm air pipes in basements shall be provided
with locking-type dampers which shall be supported on both sides of the
pipe and which shall be located not more than two (2) feet from the
furnace casing.

M-314.6 Thimbles: Warm air pipes which pass through masonry walls
shall be equipped with a metal ventilated thimble, the diameter of which
shall be at least one (1) inch greater than that of the pipe. The pipe shall
be supported in such a manner that the air space or insulation is equal
on all sides.


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M-3147 Boots or shoes: Where the return air pipe is connected to
the furnace casing at the base, the opening shall not extend higher than
fourteen (14) inches from the bottom of the furnace.

M-314.8 Vertical pipes or stacks: Vertical pipes or stacks for return
air shall not be connected to registers on more than one (1) floor.

M-314.9 Fire dampers: Approved fire dampers shall be used where
any duct passes through a required fireresistance rated wall. See Section


M-315.1 General: Prior to the installation of a conversion burner, the
contractor shall ascertain whether the entire heating system is in safe
condition for the installation of such burner and so certify in writing to
the department prior to conversion.

M-315.1.1 Furnaces in which conversion burners are installed shall be
equipped with approved high limit controls as required in Table M-303.

M-315.2 Combustion air and venting: See Articles 6 and 7.

M-315.3 Additional requirements: Conversion biuners shall comply
with the requirements of Article 6.

M-315.4 Gravity furnaces shall not be converted for use as forced air


M-316.1 Installation: Direct gas-fired makeup air heaters may be in-
stalled only in occupancies of use groups H (high hazard), S (storage)
or F (factory and industrial) unless otherwise approved by the depart-

M-316.2 Negative pressure: Direct gas-fired makeup air heaters may
be used to correct a negative pressure condition within a building where
exhaust fans are in operation.

M-316.3 Discharge: The total discharge of such equipment shall not
exceed one hundred ten (110) per cent of the capacity of the exhaust
system in conjunction with which it is used.

M-316.4 Air: All air handled by such equipment, including combus-
tion air, shall be brought in from outside.

M-316.5 Gas ratio: The ratio of gas input by volume to the total
volume of mixture discharged by such equipment shall not exceed two-
tenths of one per cent (0.2^.

M-316.6 Controls: Direct gas-fired air heaters shall be electrically
tied in with its corresponding exhaust system so that it can be in opera-


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tion only when the exhaust system is in operation. In lieu of an electrical
tie-in, equivalent reliable means to proviae this requirement, within the
limit specified in Section M-312.2.2 may be substituted if acceptable to the

M-316.6.1 Such equipment shall be provided with air-flow sensing de-
vices so designed and installed as to shut o£F the gas burner upon f sdlure
of either combustion air or main air supply (controls actuated by failure
of the power supply to the blower motor do not meet this requirement).

M-316.6.2 Such equipment shall be provided with combustion safe-
guards, including quidc-acting, manual reset safety shut-oflF valves, and
with combustion air-gas interlocks where appUcable, as required by this

M-316.6.3 Such equipment shall be provided with both a thermostatic
device (for normal operation of the gas bmner component) and a high
temperature limit control. The latter shall be set at a temperature not to
exceed one hundred twenty (120) degrees F.

M-316.7 Clearance: Such equipment shall be so installed as to not
raise the temperature of surrounding combustible material to higher
than one hundred sixty (160) degrees F.


M-317,1 General: In addition to the provisions of other portions of
this code, the following ventilation requirements described in Sections
M.317.1.1 through M-SlT.l.lS shall apply.

M-317,1.1 Ventilation is the providing and maintaining in rooms or
spaces, by mechanical or natural means, the conditioning of air which
will protect the health, safety and welfare of the occupants thereof.

M-317.1.2 The installation of all ventilating systems shall be per-
formed in conformity with the provisions of this article, the building code
and the standards Usted in Appendix B.

M-317.1.3 The ventilating requirements as herein stated shall apply
to every room designed, erected, altered or converted for the purpose

M-317.1.4 Openings shall be provided to remove excessive heat or
gases which may accumulate in a room or area.

M-317.1.5 The ventilating requirements shall be based on the purpose
for which the rooms are used, regardless of the classifications of use,
occupancy or construction in which it is located.

M-317.1.6 The method of producing ventilation and the minimum
quantities of air to be supplied and exhausted bv mechanical ventilating
systems shall be as stated in this article (see Taole M-317).


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M-317.1.7 Ventilating systems shall be provided, maintained and op-
erated to accomplish required ventilation service for all occupied areas
within the scope of this article.

M-317.1.8 Exhaust systems shall be provided, maintained and operated
for all occupied areas where machines, vats, tanks, furnaces, forges,
salamanders and any other equipment and processes in such areas pro-
duce or throw off dust or particles suflBciently light to float in the air or
which emit heat odors, fumes, spray, gas or smote, in such quantities as
to be irritating or injurious to the healdi or safety, and shall mechanically
discharge such exhaust to the outdoor atmosphere. The total outdoor air
supplied shall be equal in volume to that removed and shall be condi-
tioned to a temperature equal to the normal temperature of the space
from which the air was removed.

M-317.L9 All equipment and system service rooms which house sources
of odors, fumes, noxious gases, smoke, dust, spray or other contamination
shall be such as to prevent spreading of any such contamination to any
other occupied parts of the building.

M-317,1.10 All ventilating and exhaust systems shall be operated to
satisfy the requirements of this article during periods the building is
occupied, unless otherwise exempted by this article.

M-317.1.11 Air exhausted from bath, toilet, urinal, lavatory, locker,
coat room, kitchen, boiler room or rooms of similar use shall not be
recirculated at any time.

M-317.1.12 If a mechanical ventilating supply system only is installed
for a room, or if a greater quantity of air is supplied by a mechanical
ventilating supply system than is removed by a mechanical ventilating
exahust system for a room, adequate means shall be provided for the
natural exit of the excess air supplied. If a mechanical ventilating ex-
haust system only is installed for a room or if a greater quantity of air is
removed by a mechanical ventilating exhaust system than is supplied by
a mechanical ventilating supply system for a room, adequate means shaU
be provided for the natural supply of the deficiency in the air supplied.

M-317.1.13 The air removed bv every mechanical ventilating exhaust
system shall be discharged out-or-doors at a point where it will not cause
a nuisance, and from which it cannot again be readily drawn in by a
ventilating system, except that air which is to be used for recirculation
may be discharged to a supply system.

M-317.1.14 Mechanical exhaust from bath, toilet, urinal, locker, service
sink, closets and similar rooms shall be an independent system.

M-317.1.15 The materials used in every mechanical ventilating air sup-
ply and air exhaust system shall be of sheet metal or other approved ma-
terials. Materials shall be of non-absorbent and moisture- and corrosion-
resisting character.


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The design and construction of all equipment and the weight and
bracing of all duct work shall be such that it will operate under normal
conditions without excessive vibration. Ducts shall be substantially air-
tight. Linings, if used, shall be seciurely anchored.

M-317.1.16 Fire dampers shall be installed as required in Section

M-317.1.17 If an installation is a mechanical ventilating exhaust system
without a mechanical ventilating supply system, or if it is a mechanical
ventilating supply system, either with or without a mechanical ventilating
exhaust system, the equipment shall be su£Bcient to warm makeup air
from the seasonal low temperature (of the area in which the building is
located) to a temperature of sixty (60) degrees F.

M-317.1.18 In addition to the requirements of this article, the de-
partment may require other ventilation air where a special hazard
exists or may exist.

M-317.2 Use classification: The various uses to which the provisions
of this article apply shall be classified as follows.

Use Class !• Require ventilation on an occupancy basis. See Table

Use Class H. Require ventilation on an occupancy basis unless other-

Online LibraryBuilding Officials and Code Administrators InternaThe BOCA basic mechanical code → online text (page 6 of 27)