Cleaning an exhaust system would have to depend on how frequently the kitchen is used and what type of system that has been installed. Kitchen exhausts have hoods and ductwork to remove smoke from kitchens, but some of the exhaust gases have a residual impact on the ductwork. Generally, it is advisable to clean every three months, but if the restaurant uses wood-burning or charcoal-burning stoves, you should clean as often as two weeks, the type of fuel and how much food you cook can also be a determining factor. 

For solid fuel cooking, you should clean the exhaust systems on a monthly basis. Clean exhaust systems in kitchens that cook meals moderately on a semi-annual basis and kitchens that cook a lot of food every 24-hours. Open cooking, Chinese cooking that involves cooking on the wok should quarterly cleaning. Clean exhaust systems in restaurants that use low volume cooking, for instance, seasonal restaurants even less frequently. These are baseline requirements for cleaning, but local fire codes and the type and quantity of food might require different cleaning frequencies. 

Employees should wipe down the hood box with a non-reactive soap and water every day to protect the hood from grease. Restaurants that use solid fuel should have the spark arrestors in the wood cleaned on a daily basis. Some restaurants clean filters on a weekly basis to get rid of grease buildup but some clean daily to avoid the challenges that come with either soaking the hood filter overnight or scrapping filters to get rid of grease. Cleaning filters can also be dependent on health codes for the restaurant; some require washing in three-compartment sinks, and others allow running through a dishwasher. 

The design of hoods installed in restaurants is a very important thing to observer, as some hoods come with other filters that you should maintain or replace regularly.  Exhaust systems that have pollution control equipment also come with pressure sensors to give the users a sign that the filters are full and need to be changed;  solid fuel users with charcoal filters should change these units bi-annually or quarterly. The staff should wash filter cells by hand using detergent and hot water bi-annually. It is important to regularly inspect the parts of the exhaust system that can be cleaned with a water-wash or have self-cleaning hoods to prevent grease buildup.