Commercial kitchens that use solid-fuel cooking systems, such as hearth-type pizza ovens and those cooking systems that use wood, are at risk of fire caused by ignited creosote and grease deposits. Because creosote builds up due to restricted air supply, having a restaurant vent hood installed can spell the difference between a safe and unsafe commercial kitchen.

For the vent hood to work efficiently, however, they need to be cleaned properly and regularly as well. Otherwise, a chain reaction will occur.

What is creosote?

It is made up of condensed volatile gases that result from incomplete combustion of wood. It is created when wood smoke mixes with water vapor.

Creosote will cling to the interior of the oven and in the ductwork of an exhaust system. Because it is highly combustible, it increases the risk of fire.

According to the Chimney Safety Institute of America, the buildup of creosote is encouraged by certain conditions such as unseasoned wood, restricted air supply, and chimney temperatures that are cooler than normal.

It only takes 165 degrees F for wood tar creosote in ducts, hoods, and filters to be ignited. Considering that solid-fuel cooking requires a burning ember, flame, or spark, creosote-fueled fire is sure to happen.

How to Reduce Fire Hazards from Solid Fuel Systems

Chapter 14 of the NFPA 96, Ventilation Control and Fire Protection of Commercial Cooking Operations has provided requirements for installation and maintenance of solid fuel cooling systems.

Proper ventilation

Buildup of creosote and grease is higher if the oven and its exhaust system is not directly vented. The installation of a fully functional restaurant vent hood is an effective way to reduce fire hazard.

Regular cleaning and maintenance

• The combustion chamber must be scraped clean to its original surface once each week. In the first stage of creosote when it is still a flaky soot, it can be easily brushed away using a basic chimney brush.
• The combustion chamber must be inspected for defects and deterioration. If any are found, they must be repaired immediately.
• The exhaust system, including the restaurant vent hood, must be checked and cleaned every month by kitchen exhaust cleaning contractors. Professionals are required at this stage since glazed creosote has hardened and thickened, making it difficult to remove without the right equipment.
• Weekly inspection must be carried out with the flue or chimney if there is residue that might restrict the vent or “create an additional fuel source.”
• The flue or chimney must be checked for “corrosion or physical damage that might reduce the flue’s capability to contain the effluent.”
• Spark arrester screens must be cleaned before they become heavily contaminated and restricted. The screens are designed to “minimize the passage of airborne sparks and embers into plenums and ducts.” Left uncleaned, they will contribute to an increased risk of fires.
• The interior of the oven and the firebox must be cleaned daily. The process must be a part of your staff’s cleaning chores since it is a requirement of the standard “Solid Fuel Cooking Operations.”

Chapter 14 also recommends to use a system that automatically provides hot water and surfactant to clean daily the hood plenum and lower duct.

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