Combustion Air and Ventilation for Appliances Located in
UnconfinedSpaces
UnconfinedSpaceis a spacewhose volume is not lessthan 50
cubicfeetper. 1,000 .B.tu.perhour of theaggregate input rating of all appliancesinstalledin that space.Roomscommunicating
directlywith the space in which the appliances are installed, through openingsnot furnished with doors, are considereda part of the unconfinedspace
In unconfinedspacesin buildings, infiltrationmay be adequate
toprovide air for combustion,ventilation and dilution of flue
gases.However, in buildings of tight construction(for example, weatherstripping, heavily insulated, caulked, vapor barrier,
etc.),additional air may needto be provided usingthe methods described in Combustion Air and Ventilation for Appliances Locatedin Confined Spaces,b.
Combustion Air and Ventilation
for Appliances Located in Confined Spaces
Confined Spaceis a spacewhose volume is lessthan 50 cubic feet per 1,000 Btu per hour of the aggregateinput rating of all appliancesinstalled in that space.
a. ALLAIR FROM INSIDE BUILDINGS:
(SeePage8 Figure 1, and Figure2 below)
The confined space shall be provided with two permanent openingscommunicating directly with an additional room(s) of sufficient volume so that the combined volume of all
spacesmeets the criteria for an unconfined space. The total input of all gas utilization equipment installed in the com- bined space s.hallbe considered in making th s determina- tion. Each opening shall have a minimum free area of one squareinch per 1,000 BTU per hour of the total input rating of all gas utilization equipment in the confined spade, but not less than 100 square inches. One opening shall com- mence within 12 inches of the top and one commencing within 12 inchesof the bottom of the enclosure.
b. ALL,AIRFROM OUTDOORS: (see
The confined space shall be provided with two perma- nent openings, one commencing within 12 inches of the top and Onecommencing within 12 inches from the bot-
tom of the enclosure. The openings shall communicate directly, or by ducts, with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors.
_qrulloH LOUW_
1.When directly communicating with the outdoors, each
opening shall have a minimum free area of 1 square inch per 4,000 BTU per hour of total input rating of all equip- ment in the enclosure. (SeeFigure 3.)
2.When communicating with the outdoors through vertical ducts, each opening shall have a minimum free area of 1
square inch per 4,000 BTU per hour of total input rating of all equipment in the enclosure. (SeeFigure 4.)
CHIMNEY OR GAS VENT
VENTUL.TION LOUVERS
| AIR OUTLET |
| WATER HEATER |
| FURNACE |
| INLET AIR DUCT |
I Figure 4 l | (e_ 1'abo_ _c_) |
3.When communicating with the outdoors through horizon- tal ducts, each opening shall have a minimum free area of
1square inch per 2,000 BTU per hour of total input rating of all equipment in the enclosure. (SeeFigure 5.)
=_
I Figure 5 [
4.When ducts are used, they shall be of the
,Louversand Grilles: In calculating free area, consideration shall be given to the blocking effect of louvers, grilles or screens protecting openings. Screens used shal not be
smaller than 1/4inclh mesh. If the free area through a design of louver or grille is known, it should be used in calculat- ing the size opening required to provide the free area spec- ified. If the design and free area is not known, it may be assumedthat wood louvers will be
,Special Conditions Created by Mechanical Exhausting or Fireplaces:Operation of exhaust fans, ventilation systems, clothes dryers or fireplaces may create conditions requiring special attention to avoid unsatisfactory operation of installed gas utilization equipment.