What is the clearance factor?
The clearance factor is a coefficient that indicates how many times the height (or width) of a heat source must be maintained as a minimum distance to combustible materials. It is used when safely positioning stoves, fireplaces, chimneys and other heat sources.
How does the clearance factor work?
Every heat source radiates heat to its surroundings. The closer a combustible material is to the source, the greater the fire risk. The clearance factor expresses the ratio:
Minimum distance = clearance factor × relevant dimension of the source
For example: a stove with a clearance factor of 3 and a height of 400 mm requires a minimum distance of 3 × 400 = 1,200 mm to combustible materials.
Factors that determine the clearance factor
- Type of heat source — an open fireplace has a higher factor than a closed stove
- Surface temperature — higher temperatures require more clearance
- Insulation — an insulated chimney has a lower clearance factor
- Surrounding material — the combustibility of adjacent materials plays a role
Applications
- Stoves and fireplaces — the clearance factor determines the minimum distance to timber floors, furniture and walls
- Chimneys — the clearance factor must be observed at penetrations through roofs and floors
- Industrial installations — ovens and dryers use clearance factors
- Building regulations — codes specify minimum distances based on clearance factors
Related terms
- Fire safety
- Chimney
- Fire resistance
- Insulation
- Fire prevention
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