Fire officials along with local and state entities use the National Protection Agency (NFPA) codes as a guide line for their jurisdiction. They have the right to use the NFPA codes as loose or as strict as they like. The NFPA was founded in 1896 and has thousands of members worldwide. 

Take a look at NFPA Code 96, chapter 11.6 & Table 11.4 below and see what it says about kitchen exhaust hood
cleaning? The exhaust hood cleaning industry hinges on this code.

If a restaurant uses solid fuel cooking such as wood, the cleaning and/or the inspection must be done monthly
because burning wood gives off a lot of ash which mixes with grease and it is very flammable. If a restaurant is a
24- hour operation and is high-volume it needs to be cleaned on a quarterly basis. If a restaurant does moderate
cooking than it needs to be cleaned every six months or twice a year. And low-volume cooking operation such as
churches, day cares and such need to be cleaned once a year

Table 11.4 Exhaust Hood System Inspection Schedule of NFPA Code 96 

✓ Solid fuel cooking (wood) …………………………………………Monthly

✓ High volume cooking, 24 hr, charbroiling, wok. ……Quarterly 

✓ Moderate cooking ……………………………………………………..Semi- Annually 

✓ Low volume +cooking like churches ……………………… Annually