www.desatech.com113101-01C 7Example:Gas water heater __________ Btu/HrVent-free fireplace + __________ Btu/HrTotal = __________ Btu/Hr4. Compare the maximum Btu/Hr the space cansupport with the actual amount of Btu/Hr used._________ Btu/Hr (maximum the space can support)_________ Btu/Hr (actual amount of Btu/Hr used)Example: 51,200 Btu/Hr (maximum the spacecan support)71,500 Btu/Hr (actual amount ofBtu/Hr used)The space in the example is a confined space becausethe actual Btu/Hr used is more than the maximumBtu/Hr the space can support. You must provide ad-ditional fresh air. Your options are as follows:A. Rework worksheet, adding the space of an adjoin-ing room. If the extra space provides an unconfinedspace, remove door to adjoining room or addventilation grills between rooms. See VentilationAir From Inside Building, page 7.B. Vent room directly to the outdoors. See Ventila-tion Air From Outdoors, page 7.C. Install a lower Btu/Hr fireplace, if lower Btu/Hrsize makes room unconfined.If the actual Btu/Hr used is less than the maximumBtu/Hr the space can support, the space is an un-confined space. You will need no additional freshair ventilation.WARNING: If the area inwhich the heater may be oper-ated is smaller than that definedas an unconfined space or if thebuilding is of unusually tightconstruction, provide adequatecombustion and ventilation airby one of the methods describedin the National Fuel Gas Code,ANSI Z223.1/NFPA 54 Section 5.3or applicable local codes.VENTILATION AIRVentilation Air From Inside BuildingThis fresh air would come from an adjoining un-confined space. When ventilating to an adjoiningunconfined space, you must provide two perma-40,00031,50071,500AIR FOR COMBUSTIONAND VENTILATIONContinuedFigure 2 - Ventilation Air from InsideBuildingOrRemoveDoor intoAdjoiningRoom,Option3Ventilation GrillsInto Adjoining Room,Option 2VentilationGrillsInto AdjoiningRoom,Option 112"12"Figure 3 - Ventilation Air from OutdoorsOutletAirVentilatedAtticOutletAirInletAirInlet Air VentilatedCrawl SpaceToCrawlSpaceTo Atticnent openings: one within 12" of the ceiling andone within 12" of the floor on the wall connectingthe two spaces (see options 1 and 2, Figure 2). Youcan also remove door into adjoining room (seeoption 3, Figure 2). Follow the National Fuel GasCode ANSI Z223.1/NFPA 54, Section 5.3, Air forCombustion and Ventilation for required size ofventilation grills or ducts.Ventilation Air From OutdoorsProvide extra fresh air by using ventilation grills orducts. You must provide two permanent openings:one within 12" of the ceiling and one within 12"of the floor. Connect these items directly to theoutdoors or spaces open to the outdoors. Thesespaces include attics and crawl spaces. Follow theNational Fuel Gas Code ANSI Z223.1/NFPA 54,Section 5.3, Air for Combustion and Ventilation forrequired size of ventilation grills or ducts.IMPORTANT: Do not provide openings for inletor outlet air into attic if attic has a thermostat-controlled power vent. Heated air entering the atticwill activate the power vent.