The rating handed out by the Insurance Services Office helps differentiate the abilities of fire departments across the country. These ratings are reevaluated on a regular basis usually every 10 years or when requested. This evaluation revolves around a few categories that focus on the quality of response that a fire department provides.

The main categories that are considered in a department's ISO rating are: staffing, training, water supply, 911 system, and community outreach. 50% of the rating comes from the quality of the department revolving around the staffing and training of the personnel at the department. 40% of the score comes from the water supply available in the area. The final 10% is focused on the 911 communication system used.

The ISO ratings range from 10, being the lowest, to 1 which is the highest rating a department can achieve. Less than 0.5% of departments are able to achieve an ISO rating of 1. These ratings allow for insurance companies to adjust homeowner's insurance rates. The better rating the local fire department achieves, the lower rates citizens may have on their insurance rates.