Factory-built fireplaces and chimneys are systems, not generic collections of interchangeable parts. Model identification can change what components, clearances, terminations and modifications are permitted.
Before condemning or approving an installation, identify the appliance and chimney system when possible. Photograph labels, model numbers, components and modifications. Locate authoritative manufacturer documentation rather than relying on a visually similar product.
Missing labels or unavailable instructions create uncertainty. That uncertainty should be documented rather than replaced with a guess.
Use the official source
VerifySweep summarizes concepts for professional education. It does not reproduce or replace copyrighted code or standard text. Consult the official publication for exact requirements.
Educational content only. Codes, standards, listings, manufacturer instructions and local amendments can change which requirement applies to a specific installation.