National Fire Protection Association (NFPA) Code 96 states:
"The entire exhaust system shall be cleaned by a properly trained, qualified and certified person(s)."
Work of this nature takes specialized tools, equipment, and experience to properly and thoroughly clean the 'entire' hood exhaust system.
It is required to have a certificate of compliance indicating the name of a certified company, the cleaning date and the expiration date. It is also required to indicate if any inaccessible areas exist.