Cleaning Kitchen Hood Exhaust Systems to Minimize Fire Risk in Healthcare Facilities

The following article is from Environment of Care News, February 2023, Volume 26, Issue 2

Be sure that the ductwork is cleaned of grease all the way to the roof

Kitchens are the number-one origin site of fires in health care facilities, according to the National Fire Protection Association (NFPA). In fact, 54% of fires in health care settings start in kitchens.1 Consequently, over the past few years, Joint Commission surveyors have been focusing more and more on fire and life safety compliance in health care occupancy and large residential board and care kitchens, which is governed by NFPA 96-2011: Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations. (For a comprehensive, downloadable compliance checklist, see the “Toolbox” feature on page 15.)

One major kitchen compliance issue involves the inspection and cleaning of kitchen hood exhaust systems. This is a challenge that deserves more attention at health care organizations (HCOs), says James Kendig, MS, CHSP, HEM, Field Director-Surveyor Management and Development for The Joint Commission.

NFPA 96-2011, which is referenced by the “Environment of Care” (EC) and “Life Safety” (LS) chapters of the Comprehensive Accreditation Manuals (and their E-ditionR counterparts), requires kitchen exhaust systems (hoods, ducts, and exhaust fans), to be cleaned routinely, depending on the cooking equipment under each hood. For example, exhaust systems above charbroilers and fryers need more frequent cleaning and service than those above stack ovens, “star” ranges, or steamers.

However, what tends to happen is that exhaust hood assemblies are only superficially inspected and cleaned, notes John N. Ellis, MBA, CHFM, System Director of Facilities Management for Intermountain Healthcare in Salt Lake City, Utah.

I don’t know that kitchen hood cleaning is overlooked, but I think we don’t look far enough,” Ellis explains. “Facilities directors often think, ‘The hood is shiny; therefore, the exhaust system is clean.’ That’s not always the case.”

When inspecting or cleaning a kitchen hood, it’s critical to “look beyond the baffles and into the ductwork,” Ellis emphasizes. “I used to wonder how an entire restaurant could burn down because it had a kitchen fire,” he says. “But a fire isn’t contained in the kitchen if the duct-cleaning protocol is wrong.

As Ellis notes, “if a fire gets past the initial extinguishing system into a duct that is laden with grease, it can spread through the entire building. Our cleaning protocol must extend from the entrance of the hood up through to the exhaust pan on the roof. We have to clean every inch of that duct.” Unfortunately, that’s not what’s being done at many HCOs.

“Indeed, kitchen exhaust ducts are hidden hazards between the floors (and above the ceiling grids) of medical centers and hospitals across the country,” says Ellis. Look at the difference between the “Before Cleaning” and “After Cleaning” photos of a kitchen exhaust duct below.

Before Cleaning
Joint Commission 'Before' Photo
After Cleaning
Joint Commission 'After' Photo

A significant amount of grease can build up in a kitchen hood exhaust duct, increasing the risk of fire. It is critical for health care facilities to thoroughly clean kitchen exhaust ductwork all the way to the roof.

Dirty work

Cleaning a kitchen hood exhaust duct is dirty work, requiring specialized training and tools and the mettle of a chimney sweep. It can be done in-house but is frequently outsourced to a service contractor. Alas, kitchen exhaust system contractors often think that they are simply hood cleaning contractors, notes Ellis. “Many hood cleaning contractors do not have the equipment or the knowledge to go all the way through the duct and out to the roof,” he says. “We need to expand our view of the hood to encompass the entire exhaust system for the kitchen.”

When selecting a hood exhaust system cleaning contractor, it is thus important to find a company with the skills, equipment, and experience to clean the ductwork. Quiz prospects on their knowledge of NFPA 96-2011, and ask for references, Ellis suggests.

If cleaning exhaust ducts in house, put together a team that includes a heating, ventilation, and air-conditioning (HVAC) technician as well as a member of the kitchen staff, he advises.

Inspection procedures

Follow these steps when inspecting kitchen exhaust ducts, whether to evaluate the work of a contractor or to determine the interval between in-house cleanings:

  1. Go to the most-used cook line in your kitchen.
  2. Find the charbroiler and deep fat fryers.
  3. Remove one or two of the hood filters above the charbroiler and fryers.
  4. Find the ductwork rising from the hood plenum (the air distribution box “behind” the hood filters) and venting the grease-laden vapors from that equipment.
  5. Using a bright light-emitting diode (LED) flashlight that produces a good beam of light, shine light up and into the exiting grease duct. Lean into the cook line and inspect “up” as far as possible.
  6. Inspect and verify whether the duct is clean. (The ductwork is supposed to be as clean as the hood’s plenum.) The ductwork should not be greasier or dirtier the farther up you look. If it is, you know that your system is not being completely cleaned.
  7. If heavy grease buildup is found up the ductwork and you’re using a service contractor, call that company and ask it to complete the work per NFPA 96-2011. Since the contractor should have been providing that level of service all along, this cleaning should be done at no cost to your organization.

Additional guidelines

Compared to NFPA 96-2011, the 2021 edition of NFPA 96 has more specific guidelines related to the frequency of inspecting and cleaning kitchen exhaust systems. These newer guidelines don’t contradict the requirements in NFPA 96-2011. Ellis observes that NFPA 96-2021 guidance can be considered best practice recommendations (although The Joint Commission does not require compliance with the 2021 edition and still references NFPA 96-2011).

For example, the NFPA 96-2021 guidelines emphasize the need to clean hoods and ducts situated above high-demand, heavy-duty cooking equipment at least quarterly. For cooking equipment used less often, Ellis says, semiannual cleaning of the ductwork might be sufficient.

I would recommend that in a health care institution cooking for patients on a daily basis, clean these ducts at least quarterly,” Ellis advises.

Ellis also recommends conducting a risk assessment to evaluate the grease load that accumulates in the kitchen hood ducts. “A great way to do this,” he says, “is to clean your ducts to the bare metal, run your kitchen operation for one month, and then look at the ducts.” Any ducts that are coated with grease after this short interval should be cleaned more frequently than those that have little grease

You can prevent a lot of grease from going into the duct simply by managing grease filters properly,” Ellis adds. “Remove and clean them on a regular basis-at least monthly. Washing the filters thoroughly at least once a month protects those ducts from getting so greasy. But nothing keeps all grease away.”

1National Fire Protection Association (NFPA). Structure Fires in Health Care Facilities. Oct 2017. Accessed Dec 19, 2022.