13
•Airintaketerminalmustnotterminateinareasthatmightcontaincombustionaircontaminates,suchasnear
swimmingpools.SeeSectionIVformoreinformationonpossiblecontaminates.
6) PermittedTerminalsforVerticalVenting(VentOptions6,7)-Arodentscreenisinstalledintheendofthevent
pipe.VentmanufacturerpartnumbersforthesescreensareshowninTable4.Theairinletterminalconsistsofa180
degreeelbow(ortwo90degreeelbows)witharodentscreenasshowninFigure6.4.
7) VerticalVentTerminalLocations(VentOptions6,7)-Observethefollowinglimitationsonthelocationofall 
verticalventterminals(seeFigure6.4):
• Thetopoftheventpipemustbeatleast2feetaboveanyobjectlocatedwithin10feet.
• Theverticaldistancebetweentopoftheventandairinletterminalopeningsmustbeatleast12”.
• Thebottomoftheairinletterminalmustbeatleast12”abovethenormalsnowaccumulationthatcanbe
expectedontheroof.
• Theairintaketerminalmustbelocatedontheroofandmustbenofurtherthan24”horizontallyfromtheexhaust
pipe.
8) Wallthimbles–Wallthimblesarerequiredwheretheventpipepassesthroughcombustiblewallswithlessthanthe
requiredclearanceshowninTable4.2orasrequiredbylocalcodes.Ventmanufacturer’swallthimblepartnumbers
areshowninTable6.5.
9) PitchofHorizontalpiping–Allhorizontalventpipingmustbepitched¼”perfootsothatanycondensatewhich
formsinthispipingwillruntowardstheboiler.
10)Verticalandhorizontalsectionsofpipingmustbeproperlysupported.Seeventsystemmanufacturer’sinstructions
formoreinformation.
11) FireStops–Userestopswhererequiredbycodeorbytheventsystemmanufacturer.Consultventsystem
manufacturer’sliteratureforinformationonsuitablerestops.
Figure 6.4: Vertical Vent System (Vent Options 6,7)