Sources
Open now. No obligation.
This site does not perform the work it writes about. What it can do is be exact about the rules, and show you where every rule comes from so you can check it yourself. Every requirement, deadline and frequency stated anywhere on this site traces back to one of these.
NFPA 96: Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations
National Fire Protection Association. The standard that sets inspection and cleaning frequency by cooking volume. Local fire code adopts it.
Kitchen exhaust cleaning certification
IKECA. The certifying body most jurisdictions expect a cleaning contractor to hold.
Before you rely on this
Regulations change, and local authorities can be stricter than the state. Where this site says a rule varies by town, check with the office named on the page rather than relying on a summary.