Grease in Ventilation Systems is Largest Fire Risk In Commercial Kitchens

According to government statistics, roughly half of all structural fires in the United Kingdom are a direct result of or related to the use of cooking equipment. This is true of private residences, "public buildings", and structures clearly designated as clubs and restaurants.

Fires remain a leading cause of kitchen accidents, both in professional and private buildings. In private kitchens the leading fire causes are:

  • inattention
  • distractions
  • clutter
  • inappropriately used equipment
  • inappropriate cooking techniques
  • lack of appropriate fire suppression

Research conducted in the United Kingdom indicates that as many as 70 percent of all commercial kitchen fires originate in the ventilation systems of these establishments.

How This Happens

Commercial "vents and hoods" work by remove cooking fumes and particulates from the interior environment and leads them outside of the building. While most of this cooking waste passes without issue, some of the heavier waste (such as fat) sticks to the exterior and interior of ventilation systems. This buildup occurs on the range hoods themselves as well as the grease filters leading up to ducting and within it. In the case of grease fat particulates (which are highly flammable), waste can accumulate until it forms a thick paste. When in liquid form and used for cooking, this material can be ignited at 400 to 435 degrees Celsius. The solidification and caking of this cooking grease does not affect its flash point. The grease is also highly flammable in any form.

In the case of ventialtion system fires, active cooking is usually involved:

  • 1. Something is cooking in an open pan on a burner.
  • 2. Intentionally or otherwise, flame leaps up.
  • 3. The flame ignites built up grease on / in the range hood.
  • 4. If the flame ignites built up grease on the cooking hood filters, the hood's fan can help to propel this new flame up into the system's ducting.
  • 5. Built up grease in this ventilation ducting further propels the fire along to upper floors of a building and even its roof.

The Consequences Of Dirty Ventilation Systems

Unfortunately, the scenario described above is an all too common in commercial kitchens. Thousands of restaurant fires are reported annually. It's estimated that as many as 64 percent of them are caused by dirty hood and vent systems. What's more, this is an especially dangerous type of fire when it enters the ventilation system itself, it becomes even more difficult and dangerous to suppress. Structures with a fire propelled within its interior walls often suffer massive damage throughout the entire building, or are total losses.

How To Prevent Grease Extract Ventilation System Fires From Happening

Because of the frequency of these fires, regulations are in place that require kitchen owners to have systems both cleaned and maintained. In the United Kingdom, standards and guidance concerning the use of commercial kitchens is overseen by the Health and Safety Executive (HSE). This oversight has increasingly focused on kitchens used by professional catering concerns. Guidance on grease extraction ventilation systems (specifically gas powered ones) is also included. The 1992 Health, Safety, and Welfare Regulations specifically state that all workplaces must provide adequate ventilation for both staff and visitors. While it does not mandate specific ventilation systems, the document does focus on the hospitality and catering industries, and the importance of adequate ventilation systems for them.

The HSE document does indicate specific guidelines for the installation of gas powered ventilation systems in commercial kitchens. These systems are broken down into types that reflect system size and the exchanges of oxygen and carbon dioxide that they produce. These guidelines also apply to kitchens that use solid fuel and charcoal for cooking. Currently, the only national law that would be applicable in the case of malfunctioning ventilation systems is the Health and Safety at Work Act of 1974.

This law requires all building managers and owners to provide a safe occupancy environment for employees, tenants, and other visitors. The law also requires owners and supervisors to accept responsibility for all building issues affecting safety, including malfunctioning or poorly maintained equipment. While the HSE does not specifically compel UK restauranters and caterers to meet ventilation maintenance standards, it offers good advice in the form of a HSE newsletter.

Among its recommendations:

  • 1. The ventilation system should be appropriate for the size of the kitchen and the type of work being done there.
  • 2. The ventilation system should be professionally installed to insure peak performance and avoid malfunctioning. If a ceiling vent as opposed to a canopy (hood) system is to be used, it should be installed by professional engineers.
  • 3. Commercial kitchen owners and supervisors should establish regular system cleaning schedules conducted either by staff or professional services. Inspections should be annual. And systems should be as easy to clean and as fireproof as possible.
  • 4. When new kitchens are built, designers should be aware of systems so that kitchens can be built around them, including safety exits.

For more information, see our Maintenance Guide for Commercial Ventilation Systems and our tips on Cleaning Baffle Grease Filters.

Fires caused by dirty ventilation systems continue to be the leading cause of restaurant fires, but they don't have to be. With a proper understanding of these systems' needs, both businesses and lives can be saved.

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