The applicable standards for HVAC and kitchen exhaust cleaning mostly spell out intervals for inspection, with cleaning to be done as it is found to be needed by the inspection. That often plays out differently for HVAC vs. kitchen exhausts.
HVAC systems
For HVAC systems, the answer is actually pretty simple. The NADCA* ACR** standard calls for inspection of commercial air handling units, supply ducts, and return ducts once a year. (For residential and marine supply and return ducts, it’s every two years, but once a year for all AHUs.)
In our experience, a lot of commercial ducts don’t really need to be cleaned at these intervals, and in fact, most are not, unless there has been some sort of smoke or fire incident, or a construction project which generated a lot of dust.
*National Air Duct Cleaners Association
**Assessment Cleaning Restoration
Kitchen exhaust systems
The stakes are usually a lot higher in maintaining a kitchen exhaust system because we are talking about accumulations of fuel which sit right above a heat source and are capable of conducting a fire right through a building. For that reason, most state fire marshals including the Illinois Fire Marshal have adopted the NFPA* 96 Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations as the standard for their states. And inspections in most cases reveal a need for cleaning.
The NFPA 96 schedule for inspection of grease buildup is as follows:
- Systems serving solid fuel cooking operations**: Monthly
- Systems serving high-volume*** cooking operations: Quarterly
- Systems serving medium-volume cooking operations: Semiannually
- Systems serving low-volume**** cooking operations: Annually
*National Fire Protection Association
**Additionally, in solid fuel systems, the combustion chamber must be scraped to its original surface weekly, and the flue or chimney must be inspected weekly
***Examples include 24-hour cooking, charbroiling, and wok cooking
****Examples include churches, day camps, seasonal businesses, and senior centers
These are minimum frequencies – depending on the amount of grease accumulating in a system, it may be wise to clean more often.
Stay clean, and stay safe!