The dangers of kitchen grease are well documented. According to the National Fire Protection Association (NFPA) the frequency of exhaust system cleaning should typically be based on the type of cooking that you do.

how often should I clean restaurant kitchen hood
Although your restaurant’s baffle filters can, and should, be cleaned frequently by kitchen staff, a professional company should be hired to clean the entire exhaust system. This includes removing grease from not only the hood but also the duct and fan. Failure to have your kitchen exhaust on schedule increases your chances of a fire. Protect your investment. Remove the grease.

Westchester County Hood Cleaning
Fairfield County Hood Cleaning
Putnam County Hood Cleaning
Dutchess County Hood Cleaning