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Chimney Standard
Anatomy

Thimble

The sleeved pass-through where a connector enters the chimney.

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All glossary terms

What is Thimble?

A fitting that allows a stove or appliance connector to pass through a wall into the flue while maintaining required clearance to combustibles. An unsleeved or improperly sized penetration is a direct path from flue temperatures to framing and is treated as a serious defect.

Related terms:Pipe ConnectorClearances

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Other terms in the glossary

Creosote
Condensed wood-smoke residue on the flue wall, graded by stage — and the stage is the finding that matters.
NFPA 211
The consensus standard governing chimneys, fireplaces, vents and solid-fuel appliances.
Inspection Levels
Three defined scopes — and the standard specifies when each is required, not which you prefer.
Flue
The passage carrying combustion products out — one appliance, one flue, correctly sized.
Liner
The barrier between combustion products and the building structure. A breach takes the flue out of service.
Crown
The sloped masonry cap on top of the chimney — the surface that fails first and costs most.
15+
Years in the field
NFPA 211
Checklist
48h
Written report
< 2hr
Response
Ready when you are

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Emergency

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Chimney fire, storm hit, active leak, or a flue you're not sure about? We answer 7 AM to midnight and the assessment ends in a written safe-to-use verdict — including a do-not-use notice when the evidence supports one. After-hours dispatch runs subject to crew availability.

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