Black spots around a window

Small dark marks can come from surface mold, soot deposition, dirt held by condensation or degraded sealant.

∴

Urgency profileInvestigate

Use timing, location and checks to separate competing explanations.

Do not identify growth by color alone

Pattern, moisture history and surface temperature are more useful than color. If marks return, examine humidity, airflow and the coldest edges.

Observe→Distinguish→Control source→Verify

Living dossierPublished knowledge is connected and improved as new cases, images and outcomes are added. Updated 2026-07-20.