Chandler Burning Index (CBI)

The Chandler Burning Index is a metric used to assess fire danger severity based on temperature and humidity. The higher the value, the greater the fire risk.

Formula

The CBI is calculated using the following formula:

CBI = (((110 - 1.373 * RH) - 0.54 * (10.20 - T)) * (124 * 10^(-0.0142 * RH))) / 60

Where:

• RH: Relative Humidity (%)

• T: Temperature (°C)

Fire Danger Levels

• Low (CBI < 50): Fires are unlikely to spread rapidly. Spotting is rare.

• Moderate (CBI 50–75): Fires can start from most causes and may spread briskly in grasslands.

• High (CBI 75–90): Fires start easily and spread quickly, especially in dry areas.

• Very High (CBI 90–97.5): Fires ignite and spread rapidly; spotting is common.

• Extreme (CBI > 97.5): Fires start instantly, spread uncontrollably, and are highly dangerous.

Use in Wildfire Management

CBI values help guide firefighting readiness, public warnings, and resource deployment. By monitoring changes in relative humidity and temperature, fire agencies can better assess short-term fire risks and adjust alert levels accordingly.

The CBI is particularly useful for:

• Determining burn bans and fire restrictions based on elevated fire danger.

• Supporting decisions on allocating aerial and ground firefighting resources.

• Issuing public fire danger warnings via signage or media during high-risk periods.

• Assisting land managers in assessing the safety of prescribed burns and controlled fire operations.

Its simplicity and reliance on widely available weather parameters make the CBI especially practical for regions without access to more complex fire modeling tools. However, for comprehensive risk management, it is often used in combination with other indices and local knowledge.

Limitations of CBI

While effective, the CBI does not account for wind, fuel moisture, or fuel load. Integrating it with other tools and local knowledge can improve decision-making.

Sources and References

• Arthur's Pass Fire Weather Index Calculator

• Stillwater Weather: Chandler Burning Index

• University of California – Original CBI Documentation (Craig Chandler)