The core idea
Combustion odor, soot or alarm events can signal unsafe venting and should stop normal self-help investigation.
How the mechanism works
Depressurization, blocked flues or appliance faults can spill combustion products into occupied space.
When it becomes relevant
Typical trigger: Appliance operation, exhaust fans, cold starts or wind.
Evidence that supports this interpretation
- Odor or soot appears near combustion equipment
- Alarms activate
- Symptoms change with exhaust devices
Evidence that weakens it
- The equipment is verified off and isolated
- The odor is clearly non-combustion
- Qualified testing has ruled out spillage
What this concept cannot prove alone
A single observation, image or meter reading cannot confirm the complete failure pathway. Use this concept to form better questions, compare alternatives and decide which safe observation would be most informative next.
Safety and professional boundary
This is a hard safety boundary: do not perform smoke tests, disable alarms or continue appliance operation.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
