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RELIABLE VENTING
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SPILLAGE POSSIBLE
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SPILLAGE LIKELY
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Chimney
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installed inside building envelope
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half in/half out
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installed outside envelope
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higher than top of envelope
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same height as envelope
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lower than top of envelope
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sized to match appliance outlet
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one size smaller or larger
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too big/too small
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high mass
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moderate mass
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low mass
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well insulated
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some insulation
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not insulated/air cooled
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straight up
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slight offset
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severe/multiple offset(s)
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sealed
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somewhat leaky
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leaky
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Flue pipe (if applicable)
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sized to match appliance outlet
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one size larger or smaller
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too large/too small
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straight up
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one elbow
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more than one elbow
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tight joints
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loose joints
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leaky joints
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no obstructions/major leaks
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key damper or barometric draft control
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flue pipe heat exchanger
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total length less than 6'
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between 6' and 10'
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more than 10'
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Appliance
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gas/propane appliances
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sealed/direct vent
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induced draft
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draft hood
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oil-fired appliances
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sealed with induced draft
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induced draft
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barometric draft control
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woodburning appliances
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gasketed doors
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leaky doors
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open — no doors
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adequate internal flow area
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somewhat restrictive
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very restrictive internally
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updraft — no internal by-pass
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sidedraft/downdraft/catalytic — internal by-pass damper
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high mass
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moderate mass
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low mass
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round firebox outlet
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rectangular firebox outlet
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slot firebox outlet
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EPA certified (stable combustion)
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some combustion design (may smolder)
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no combustion system (may smolder)
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Building environment
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The relative tightness of the building envelope is a factor in venting performance but a reasonably tight envelope does not necessarily contribute to spillage and a loose envelope does not guaranty reliable venting. The related features are the total mechanical exhaust capacity and how it is used.
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balanced ventilation
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no ventilation system
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exhaust-only ventilation
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no large mechanical exhausts
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moderate exhaust capacity
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high volume mechanical exhausts
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