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I Provision for combustionand ventilation air must be in accordance with Section5.3, Air for Combustionand Ventilation, of
the National Fuel Gas Code, ANSI Z223.1-1atest revision, or applicable provisionsof the local building codes.
WARNING
Be sure to provide enough fresh air for combustion.
Enough air insures proper combustion and assures that
no hazard will develop due to the lack of oxygen.
Youmustprovideforenoughfreshairtoassurepropercombustion.Thefire
in theboilerusesoxygen.It musthaveacontinuoussupply.Theair in a
housecontainsonly enoughoxygentosupplylhe burnerfor ashorttime.
Outsideair mustenterthehouseto replacethatusedbytheburner.Study
followingexamples1and2 to determineyourfreshair requirements.
EXAMPLE1: Boiler Locatedin UnconfinedSpace
Anunconfinedspaceis definedas aspacewhosevolumeis not lessthan
50cubicfeelper1,000Bluperhourof thelotalinputratingof allappliances
installedin thatspace.
Ifyour boileris inanopenarea(unpartitiouedbasement)in aconventional
house,theairthatleaksthroughthecracksarounddoorsandwindowswill
usuallybeadequateto provideair forcombustion.Thedoorsshouldnotfit
tightly.Donotcaulkthecracksaroundthewindows.
Equipmentlocatedin buildingsofunusuallytightconstructionshallbepro-
videdwith airfor combustion,ventilation,anddilutionol fluegasesusing
themethodsdescribedin example2Borshall bespeciallyengineered.The
authorityhavingjurisdictionmustapprovespeciallyengineeredinstalla-
tions.
EXAMPLE2: Boiler Locatedin ConfinedSpace
/L All Air from Insidethe Building:Theconfinedspaceshallbepro-
videdwithtwopermanentopeningscommunicatingdirectlywithanaddi-
tional room(s)of sufficientvolumeso thatthecombinedvolumeof all
spacesmeetsthe criteriafor anunconfinedspace.Thetotalinput of all
gas:utilizationequipmentinstalledin thecombinedspaceshallbecon-
sideredin makingthis determination.Eachopeningshall havea mini-
mumfreeareaof onesquareinchper1,000Btuperhourolthetotalinput
ratingof all gasutilizationequipmentin theconfinedspace,butnot less
that100squareinches.Oneopeningshallbewithin12inchesof thetop
andonewithin12 inchesof the bottomof theenclosure.Theminimum
dimensionof airopeningsshallnolbelessthan3 inches.
B. All Air from Outdoors: Theconfinedspaceshallcommunicatewiththe
outdoorsinaccordancewithmethods1or 2.Theminimumdimensionof
airopeningsshallnot belessthan3 in. Whereductsareused,theyshall
beof thesamecross-sectionalareaas the freeareaof theopeningsto
whichtheyconnect.
1. Twopermanentopenings,onecommencingwithin 12 inchesof the
top,andonecommencingwithin12inchesoftheboltom,oltheenclo-
sureshallbeprovided.Theopeningsshallcommunicatedirectly,orby
theducts,withtheoutdoorsor spaces(crawlor attic)thaifreelycom-
municatewiththe ouldoors.
a)Wheredirectlycommunicatingwiththeoutdoorsor wherecommu-
nicatingto theoutdoorsthroughverticalducts,eachopeningshag
haveaminimumtreeareaof 1sq. in. per4000Btuperhourof total
inputratingof all equipmentin theenclosure.(SeeFigure3A.)
b)Wherecommunicatingwiththe outdoorsthroughhorizontalducts,
eachopeningshal!havea minimumfreeareaof 1sq.in. per2000
Blu perhourof totalinputratingof all equipmentin theenclosure.
(SeeFigure3B.)
2. Onepermanentopeningcommencingwith12 inchesof thelop of the
enclosure,shallbepermittedwherethe equipmenthasclearanceofat
NOTE
If you use a fireplace or a kitchen or bathroom exhaust
fan, you should install an outside air intake. These
devices will rob the boiler and water heater of combus-
tion air.
least1 inchfromthesidesandbackand6 incheslromIhefronlof the
appliance.Theopeningshall directlycommunicatewithIhe outdoors
or shallcommunicatethrougha verticalor horizonlalductto theoub
doorsor spaces(crawlor attic)thatfreelycommunicatewiththeout-
doors,andshallhaveaminimumfreeareaof:
a) 1sq. inchper3000Btuperhourol theIolalinputof aftequipment
locatedin lheenclosure(SeeFigure4),and
b)Notlessthanthesumof theareasof allvenlconnectorsinthecon-
finedspace.
Figure 3A - FRESH AIR DUCT CAPACITIES (Btuh) i
Fresh Air
Duct Size
3"x 12"
8" x 8"
8" X 12"
81/2" X 16"
1 Square Inch per 4,000 Btuh
100% Free 75% Free
Area Area
1/4"Wire Metal
Mesh Louvers
144,000 108,000
256,000 192,000
384,000 288,000
512,000 384,000
25% Free
Area
Wood
Louvers
36,000
64,000
96,000
128.000
I 3B - FRESH AIR DUCT CAPACITIES (Btuh) I
Figure
1 Square Inch per2,000 Btuh
Fresh Air
Duct Size
3" x 12"
! 8" x 8"
8"x 12"
81/2" x 16"
100% Free 75% Free
Area Area
V4" Wire Metal
Mesh Louvers
72,000 54,000
128,000 96,000
192,000 144,000
256,000 192,000
25% Free
Area
Wood
Louvers
18,000
32,000
48,000
64,000
I FRESH AIR DUCT CAPACITIES (Btuh) i
I
Figure
4
1 Square Inch per 3,000 Bruh
100% Free 75% Free 25% Free
Area Area Area
Fresh Air V,¢'Wire Metal Wood
Duct Size Mesh Louvers Louvers
3" x 12" 108,000 81,000 27,000
8" x 8" 192,000 144,000 48,000
8" x 12" 288,000 216,000 72,000
8V2"x 18" 384,000 288,000 96,000
5