⌂HouseSymptomsHOUSE INTELLIGENCE

12 complete symptom paths42 guides and 60 questions in each 1,460 Grade A articlesOne searchable, connected knowledge library 140 official sourcesEvidence context with explicit limits

Failure Fingerprint

Soot deposition on a cold surface

Airborne particles collect preferentially at cold or high-airflow patterns.

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Typical location

Cold framing lines, window edges and surfaces in particle-laden air

Timing fingerprint

Builds gradually during heating seasons or combustion exposure

Visible or audible pattern

Dry gray-black smudging that follows airflow or thermal patterns

Best separating check

Compare wipe texture, moisture history and distribution across cold lines

Evidence that weakens this cause

Soft or fuzzy material that regrows after damp conditions

Do not confuse it with

Open a side-by-side comparison

Surface growth vs soot depositionTexture, wetting and distribution help separate dark biological spotting from airborne particles.→