The 'M&Ms' of ISO's Fire Class Rating Systems Explained

The Insurance Services Office rating system can be daunting, but a Firehouse Expo presenter explained the myths and mysteries surrounding it.


“The results of your work is what really counts,” Curl said. “It’s not about ISO. It’s about the service you provide to your communities.”

Curl explained that 50 percent of the score comes from examinations of fire department training, equipment, locations and a myriad of other elements controlled by the fire department.

Forty percent of the score is derived from the water supply system in a community, even those without hydrants and only static water supplies, Curl said. And Gibson, the ISO manager, said it is possible for departments without hydrants to get full credit for water supply provided they are able to deliver adequate water flows from other sources.

The final 10 percent comes from the communications system, Curl said, adding that it’s often a function of the county or other department. ISO evaluators will check out the services dispatch provide and assign a grade accordingly which is then all factored into an algorithm Curl said.

“Don’t think they’re out just to get you,” Curl said. “They’ll work with you. They’ll give you help. And at the end of the day, what you do, or don’t do, will show.”