by Lemuel L. (Speedy) Laster

Kitchen managers often think that their health & safety inspections are over after they find that the worktops are clean, the pots are bright and shiny, and the filter banks are grease free. They may be completely unaware that the biggest hazards may be invisible to them, higher up in the hood and ventilation system. If these areas do not receive regular inspections and maintenance performed by professionals who understand these systems and who are committed to doing a thorough job, it’s only a matter of time before serious problems will arise.

Hidden Hazards Revealed by Thorough Inspections

Here is a case in point. Recently, as part of our “Inspecting Commercial Kitchen Systems” two day seminar, I was leading a group through a site inspection of a CKV (Commercial Kitchen Ventilation) system. These site inspections are often the highlight of our seminar and receive rave reviews because they bring theory into crisp perspective. We were discussing the importance of getting up inside of the system, and looking behind the filter bank through the plenum area and into the lower ducting.  

Upon doing so in this case, we discovered that the extraction system was seventeen years old. We found a damper and decided to check it for functionality. At this point you may be thinking, “No big deal. There are many systems out there this age or older with dampers in their CKV’s” and you would be right. However, a fusible link held this one open. There was no record of inspection of this link since the time of commissioning. Why? Because it was not on the maintenance schedule. So why was this a problem?

The fusible link was still intact, and theoretically would have closed the damper in the event of overheating despite being seventeen years old. However, the N.F.P.A. 96 Standard requires replacement of these CKV damper fuses every six months and for very good reason. These systems are “dumb”. If a fusible link breaks as a result of old age, or fails for any other reason during the cooking process, the damper shuts down, and the H.V.A.C. returns the vapor, gas fumes and smoke from the cooking process back into the facility. Obviously this is a big problem.  

In this event, under normal circumstances, a trained kitchen staff would activate their fire alarm, turn the gas and electricity off and vacate the room following a rehearsed procedure. However, this particular kitchen was in a day-care facility for small children. You can imagine the panic and potential for serious injury that a rushed unrehearsed evacuation might cause. Remember,we are dealing with small children here.

The Importance of Proper Training

This case study demonstrates a major problem with CKV kitchen exhaust systems. An expert may succeed in a proper installation but may fail when it comes to technology transfer training. In other words, he may not clearly explain to the facility owner how they need to be maintained (ie. There is a damper and a fusible link that must be inspected). Even if they do, the facility owner may not follow through or pass the information along to specialized maintenance personnel. Inspectors may then fail to conduct an in-depth inspection, identify the problem and report it to the owner. Either way, the end result is the same and is all too common, the CKV contains a hidden hazard that poses a real health and safety risk.

The requirements of the governing codes are paramount in the protection of life and property.  It is vital that facility owners and inspectors know the different components of a CKV system, along with proper inspection techniques. The dangers involved with commercial cooking systems are many. As is illustrated above, you do not necessarily have to have a fire in an exhaust system to endanger lives.

About Speedy Laster

As a lead instructor, Speedy has traveled throughout the US, Canada, Europe and Asia  teaching Phil Ackland’s “Inspecting Commercial Kitchen Systems” course.  As a subject matter expert, he is a main contributor to Phil Ackland’s “Inspecting Commercial Kitchen Systems” reference manual.

About Phil Ackland

Phil is a member of the NFPA 96 Committee. He has written severalbooks on inspecting and the investigation of commercial kitchen systems fires. Thousands of kitchen managers, fire inspectors, fire investigators, building inspectors and other industry professionals throughout the US, Canada, Europe and Asia have attended Phil Ackland’s ICC accredited one and two day seminars.

Attend One of Our Seminars

Phillip Ackland Holdings offers two main courses focusing on Commercial Kitchen Systems, “Inspecting Commercial Kitchen Systems” and “Prevention and Investigation of Commercial Kitchen Fires”   Dates and locations for these seminars are posted and updated regularly on our website. If you would like to have a seminar scheduled in your area contact our event coordinator, Samuel Musico (sam@philackland.com).

Fire Investigations and Expert Witness Testimony

Phillip Ackland Holdings offers industry leading commercial kitchen fire investigations as well as expert witness testimony. Law firms and insurance companies call upon us to support and win their cases. Contact us at info@philackland.com to request a current rates sheet.

We Value Your Input

Please email us at info@philackland.com if you have suggestions, or points you would like to see included in this post.

In the commercial kitchens and restaurants, the deep fat fryer is one of the most susceptible appliances for serious fires.

What is a Deep Fat Fryer?

Illustration of how grease can accumulate in the flue gas exhaust of a typical deep fryer.

A deep fat fryer (also called a fryolator, French fryer, or open vat fryer) is a vat, or multiple vats, filled with cooking oil that is heated by burners running through tubes underneath.  The tubes may serve as a heat exchanger for a gas burner, or electric coils. Baskets of food are submerged in cooking oil heated from 163ºC to 191ºC (325ºF to 375ºF).

What Causes Deep Fat Fryers to Ignite?

There are three primary reasons for ignition:

1. Poor Mechanical Maintenance
   Open fryers are particularly susceptible to poor mechanical maintenance.  Normal cooking temperature for deep fryer vegetable oil is about 191ºC (375ºF).  Thermostat malfunction is a primary cause for deep fryer fires in restaurants. If a thermostat malfunctions, cooking temperatures can rise. At 218ºC (424ºF) oil starts to smoke.  Smoke production will increase as the temperature rises.  Auto ignition takes place at approximately 273º to 420ºC (523º to 788ºF),depending on the type of oil, the amount of impurities in it and usage.  New “high-temperature” fryers are designed to maintain the heat of the oil longer and cook at higher temperatures (much closer to auto-ignition), making these units a more significant fire risk.  Appliance manufacturers should be involved in notifying end-users that new “high-temp” fryers require upgraded fire-extinguishing systems.
2. Fryer Chimney Grease Buildup
   In nearly all fryer designs, the flue gas exhaust vent for the heat from the burner elements (whether gas or electric) goes up the back of the unit behind the vat.  With repeated splashing a substantial coating of grease can build up and harden on top of and around this exhaust stack (like creosote in a wood burning chimney).  This residue provides an excellent fuel source especially if some of the buildup falls close to the burner elements below.  Most new fryers are constructed with the chimney open at the bottom, so any debris that falls down the gas flue chimney should fall straight to the floor.
3. Inadequate Clearances to Combustibles
   NFPA 96 requires a clearance of at least 406 mm (16 in.) between fryers and any open flame burners.  A 203 mm (8 in.) metal or tempered glass panel can be used to achieve this clearance. If this clearance is not met, open flames can ignite the  cooking oil.

There must be a 16” gap between the fryer and any open flame. This can be achieved with a spacer (8”and 8”).

What to do if Your Case Involves a Deep Fat Fryer Fire?

Thermostatic controls and electronic ignitors are sophisticated components ensure that your subject expert has a solid understanding of the workings of the deep fryer involved.  If the deep fryer was the original source of the fire (point of ignition), the appliance should be saved, examined, and tested in a professional lab.  Onsite probing or disassembly of the controls should be avoided. A laboratory examination of the fryer can reveal that the safety devices have been tampered with, there has been an overheating of an empty vat causing metal fatigue, and/or improper or inadequate maintenance of the unit has recently taken place.

See additional articles on philackland.com.

Phil Ackland has been in the field of commercial kitchen fire investigation and education for over 40 years. https://www.philackland.com/. He sits on the NFPA 96 committee, has been a qualified expert witness and is a consultant to attorneys and insurance companies. He has written a series of books on these systems.  The most recent A Guide for Commercial Kitchen Fires – Prevention and Investigation. His seminars have been attended by 1000’s of fire inspectors and fire investigators. https://www.philackland.com/courses/

Mark Finck has extensive expertise in all aspects of commercial cooking equipment and a comprehensive background in kitchen operations.  Mark has served on the NFPA 96, ASHRAE and other safety code committees. He is a subject matter expert in commercial kitchen ventilation, appliances and flame broilers.     https://www.philackland.com/fire-investigation/the-associates/mark-finck/

In the introduction to understanding fires in commercial kitchen exhaust systems, commonly called restaurant grease fires, we highlighted the importance of understanding cooking appliances, combustible grease, and the effects of fire spread.

In this article we will discuss the purpose of fire investigation. The fundamental Origin and Fire Cause Objectives of a fire investigation are to:

• Determine the origin of the fire, the location where the ignition source and the fuel came together to start a fire.
• Determine the fire cause, the circumstances or conditions that brought the ignition source, fuel, and oxygen together resulting in the fire.
• Determine the development and spread of the fire.

An example of the purpose of an investigation applied to commercial cooking equipment related fire investigation would be as follows:

• The origin (location) of the fire was in the area of a deep fat fryer.
• The fire cause was the ignition of cooking oil in the fryer, and the ignition was brought about by the failure of the fryer’s high limit switch.
• A fire resulted. It spread into the hood and duct system, where the accumulation of grease residues was a factor in the spread of the fire into the rest of the building.

In many cases, the purpose of the investigation may go beyond determining fire origin and cause, and include the examination of circumstances that led to property damage, bodily injury or loss of life — the cause of the loss. Further, the investigative assignment may require that the investigator determine, through analysis of the facts, the responsibility of a party or parties regarding those circumstances or conditions that brought about the cause of the loss.

In the above fryer fire example, in investigating the cause of the loss, the investigator may conclude that the fire spread beyond the hood and duct system to involve the structure due to an operational failure of the fire-extinguishing system. A detailed examination of the cooking and exhaust equipment and its installation and maintenance may determine that other parties are responsible for the failures. (Note: The 2004 edition ofNFPA 921 Guide for Fire and Explosion Investigations makes an important distinction between the terms “Fire Cause” and “Cause.” See NFPA 921 Chapter 3, Definitions.)

The scope of a specific fire investigation will depend on the role of the investigator. Typically, a fire department investigator or fire marshal will be concerned with the three fundamental Origin and Fire Cause objectives listed above in addition to the determination of whether the cause was accidental or intentional. The findings may lead to improved fire prevention.

A fire investigator retained by an insurance company may have a broader responsibility beyond Fire Origin and Cause to also make a determination regarding those factors contributing to the Cause of the Loss. Further, with the assistance of engineers or equipment experts, an examination and analysis may include the determination of specific equipment failures and parties responsible for those failures.

By Phil Ackland

Series Introduction

This is the introductory article to a series on better understanding fires in commercial kitchen systems. Over the next few months we will be adding to this series with various topics that a fire investigator needs to know when investigating commercial kitchen fires.

Fires involving commercial cooking equipment are a significant part of the U.S. fire problem. According to NFPA statistics an annual average of 11,100 fires take place in eating and drinking establishments. The origin of one-half of these fires was in the kitchen – the location of heat producing appliances.

Applying the principles of fire investigation in commercial kitchens requires an understanding of:

• the operation of the commercial kitchen
• how the cooking appliances relate to each other
• the production of combustible grease accumulations
• how those accumulations affect the spread of a fire
• the expectations of the fire resistant construction installation
• the maintenance of the exhaust system and the operation of the fire suppression system

Stages of a kitchen grease fire

Food preparation requires heat, in most cases supplied by natural gas. Cooking food results in the production of grease vapors, which are drawn up into the exhaust system by a fan. These combustible grease residues rapidly recondense within the exhaust system, accumulating a fuel load over time and retarding the ability of the exhaust and suppression system from operating as designed. Cooking appliance malfunction, excess oils or human error will cause ignition of oils and create sustained flare-ups (uncontrolled burn). The impinging heat (flames) from the initial uncontrolled burn can have sufficient energy to ignite the grease residue on filters and in the hood, creating spread.

Once ignition within the hood area takes place, several factors will determine whether combustion continues and the intensity of the uncontrolled burn, including:

• continuing heat from the initial uncontrolled burn on the appliance
• the proximity of the appliance to the hood area
• failure of the fire suppression system to operate as designed
• grease accumulation within the exhaust system
• actions (or lack of action) by the kitchen staff

Under normal conditions, air movement provided by the fan supplies all the oxygen necessary to sustain burn. This air movement now encourages the fire up into the ductwork. Radiant heat from a fire within the duct often ignites structural materials, spreading the fire out of the exhaust system and into the building. If the fire reaches the fan, heat from the melting of aluminum fan will drip onto combustible roofing materials, igniting these surfaces.

This is the ‘typical’ spread of a serious, building-damaging kitchen fire. There are, of course a number of other variables.

Nearly all of these possibilities are supposed to be prevented by proper construction, installation and maintenance to fire and building codes standards. But, simply put, many commercial kitchen exhaust systems are not installed or maintained according to the Fire Code.

By Phil Ackland