IF YOU CAN’T STAND THE HEAT … FACING THE CHALLENGE OF COMMERCIAL KITCHEN FIRES

Every year restaurant fires, typically starting in the kitchen, risk the lives and livelihoods of staff and diners and cost proprietors millions of dollars in lost revenue and repairs. Yet these fires are preventable with appropriate suppression systems, effective cleaning and grease removal regimes, and safe working practices.

BOB GRIEVE

Around 26,210 cafes and restaurants in Australia employ over 111,200 people and have a total value of around $14 billion. These establishments operate in a climate of tight margins and strong competition, so efficiency and cost-effectiveness have never been more important.

They can quickly become undone by an out-of-control kitchen fire.

Australian kitchen fire statistics are difficult to come by, but the National Fire Protection Association (NFPA) reports an average of 11,100 fires take place in eating and drinking establishments every year across the US, half of which originate in the kitchen.

Obviously, cooking equipment poses a particular problem, with builtup grease from flammable cooking oil in deep-fat fryers, cooking ranges, and cooking grills increasing fire risk.

This equipment needs to be cleaned and maintained regularly, but it is equally vital to protect the ductwork because grease vapours given off when cooking nearly all types of food will accumulate on the hood, in the ducts, and on the fan of the exhaust system. This residue is combustible at approximately 370°C, while a cooking appliance flare-up can easily reach 1,100°C, potentially causing an uncontrolled fire that can be quickly ‘sucked’ through the entire length of the duct.

Protecting the cooking equipment is only part of the kitchen fire safety equation. It is equally vital to protect the ductwork.

But there are solutions: ‘tailored’, bespoke or engineered systems; pre-engineered systems; and portable hand-held extinguishers can all help to ensure that the only thing on fire in the kitchen is a flambé.

Tailored fixed fire suppression systems are, as the term implies, designed for the conditions and needs of the individual kitchen.

Pre-engineered systems do not require the involvement of a design engineer beyond the original product and system configuration. They are made of pre-designed components and are, by far, the most popular solution for commercial kitchen fire suppression.

Portable extinguishers, while no substitute for pre-engineered fixed suppression, also have a valuable role to play in ensuring kitchen fire safety.

Unfortunately, water suppression tends to be ineffective, particularly when compared with the quick knock-down, cooling, and smothering action of wet chemical systems.

A report by the Fire Equipment Manufacturers’ Association titled Wet Chemical Pre-Engineered Restaurant System/Water Sprinkler System

Comparison concluded that:

“… water sprinkler systems do not always compare favourably with wet chemical systems, and, in fact, there are some important reasons why wet chemical systems are most often preferred by the industry’s authorities having jurisdiction and end users … … pre-engineered wet chemical systems provide complete protection to all hazards simultaneously and are UL tested and listed specifically for restaurant hazard applications. Agent characteristics, simultaneous coverage, and specific test criteria make preengineered wet chemical systems the state-of-the-art fire protection system for restaurant application and the choice of the industry’s buying influences.”

There are a number of relevant standards that can give good guidance, depending on the type of system installed. These include:

„ UL 300 Fire testing of fire extinguishing systems for protection of commercial cooking equipment, first introduced in 1994, but since amended and updated

„ AS/NZ 1668 Set-2012 The use of

„ AS 1851-2012 Maintenance of fire protection systems and equipment

„ AS 2118 Automatic fire sprinkler systems

„ AS 3772-2020 Pre-engineered fire protection systems for cooking equipment

„ NFPA 96-2021 Standard for ventilation control and fire protection of commercial cooking operations

„ NFPA 13-2022 Standard for the installation of sprinkler systems

„ NFPA 17a-2021 Standard for wet chemical extinguishing systems

„ LPS 1223 Requirements and testing procedures for the LPCB certification and listing of fixed fire extinguishing systems for catering equipment.

UL 300 is a fire test method that applies to pre-engineered extinguishing systems intended for the protection of commercial cooking areas, protecting appliances, plenums, and ducts.

It considers the characteristics of these systems, including their selfcontained supply of extinguishing agent, which is generally available in limited quantities and is discharged over a short period of time.

Pre-engineered kitchen fire suppression systems should be installed to AS 3772 and tested to UL 300 to ensure that they are able to extinguish test fires quickly, providing assurance to business owners, fire brigades, regulators, and insurance providers alike.

It is vital that suppression systems are performance tested. However, this can really only be achieved with a pre-engineered system—by definition, tailored, bespoke, or engineered solutions cannot undergo any performance testing regime. Performance is substantiated only by theoretical calculation, so these solutions do not comply with UL 300. The most sophisticated of these pre-engineered systems can be triggered automatically or manually and offer the option of either:

„ an ‘appliance-specific’ design, where nozzles are aimed at the particular fire hazard areas of each appliance

„ an ‘overlapping’ design, where discharge nozzles are configured to overlap and provide a ‘fire-free zone’ across a group of appliances, protecting them even if they are replaced or rearranged under the hood.

Both types quickly detect and suppress high-temperature cooking oil fires, using proven fusible-link, pneumatic tubing, and Linea detection and release system technology. This ensures that, when the system detects a fire, the gas or electric power to appliances is cut off immediately.

By definition, tailored or engineered solutions cannot undergo any performance testing regime. Performance is substantiated only by theoretical calculation, so these solutions do not comply with UL 300.

The ‘appliance-specific’ design invariably provides the most economical use of the suppression agent. It reduces the size or number of storage cylinders and associated hardware needed.

Until the early 1990s, the predominant fire suppression agent for kitchen systems was dry chemical powder but, with the advent of UL 300, these were superseded by higher-performing wet chemical systems. No dry chemical systems have ever passed the UL 300 testing standard.

The most advanced wet chemical suppression agents used in preengineered kitchen fire suppression systems ensure that vapours in the cooking appliance, plenum, and ductwork areas are contained and cooled. These advanced formulations quickly knock down flames and cool hot surfaces, while generating a robust vapour-securing blanket that helps prevent reignition. A bonus of this suppressant is that, with a nearly neutral pH, it is exceptionally friendly to cooking equipment and does not damage stainless steel surfaces.

Portable suppression Agent selection is equally important when considering portable hand-held extinguishers, due to the nature of Class F fires that involve cooking oils and fats such as olive oil, maize oil, sunflower oil, lard, and butter.

Portable extinguishers are a valuable first line of defence and, like fixed kitchen fire suppression systems, are subject to a number of regulations and standards, including:

„ AS/NZS 1850-2009 Portable fire extinguishers—classification, rating, and performance testing

„ AS 2444-2001 Portable fire extinguishers and fire blankets— selection and location

„ AS/NZS 1841.1-2007 Portable fire extinguishers—general requirements

„ AS/NZS 1841.3-2007 Portable fire extinguishers—specific requirements for wet chemical type extinguishers

„ UL 300, which stipulates that because of the risk of Class K fires— the US equivalent of Australia’s Class F fires—a Class K portable fire extinguisher is now required in all commercial kitchens.

In Australia, pre-engineered systems are installed to AS 3772, and are supported by authorised distributors and the manufacturers. Inspection and testing is carried out every six months with mandatory component replacement and cleaning. Training is provided by the manufacturers to UL and NFPA standards.

Delta Fire Australasia Pty Ltd is a fire protection company located in Queensland, NSW, and Victoria with particular expertise in special hazards fire systems.