Kitchen Hood & Duct Fire Sprinkler Systems

Australian Standard AS2118.1 specifies the requirements for the design, installation and commissioning of automatic fire sprinkler systems in buildings, including areas around commercial type cooking equipment in kitchens and associated ventilation systems. Where the cooking equipment includes a deep fat fryer, there are other considerations that installers and maintainers MUST take into consideration.

CEO, Firewize
11 Feb, 2021
Commercial Kitchen & Kitchen Hood

Buildings fitted with a required automatic fire sprinkler system designed to Australian Standard AS 2118.1 that include a commercial kitchen will also incorporate cooking equipment, kitchen hoods and associated ventilation systems (including exhaust ducts).

The Standard is prescriptive about the location of sprinkler heads as follows;

  1. under kitchen hoods, not more than 3.6 meters apart; and
  2. in horizontal ducts 4 meters apart;1 or
  3. at the head of a vertical rising duct.

Where the cooking equipment includes a deep fat fryer, there are other considerations that installers and maintainers MUST take into consideration.

AS 2118.1:2017 - Clause 5.9.14
Commercial type cooking equipment and associated ventilation systems Sprinkler protection shall be provided under hoods, and above cooking equipment and associated ventilation systems designed to carry away grease-laden vapours. Sprinklers shall be located not more than 3.6 m apart under hoods, 4 m apart in horizontal ducts, and at the head of all rising ducts. The first sprinkler in a horizontal duct shall be installed adjacent to the duct entrance.

The system shall be designed so that a cooking surface fire will operate the sprinklers protecting the cooking surface prior to or simultaneously with those protecting the connected ductwork.

Sprinklers shall be arranged to prevent water from directly impinging on the surface of deep fat fryers. Where this is accomplished by the provision of a shield or baffle it shall be located so that it will not interfere with the sprinkler discharge to the areas required to be protected.

When a sprinkler protecting the cooking surface operates, it shall initiate fire alarm control systems, and isolate the fuel supply to the cooking equipment.

Oil & Water Fire (they definitely do not mix)

We all know that oil (grease) and water don't mix, but this is particularly important when it comes to very hot oil. The issue arises because water when it transforms from a liquid to a vapour (steam) expands explosively over 1600x its original volume.

AS 2118.1 covers this circumstance with some direction for installers however there is some confusion about the requirements set out in the Standard.

AS2293.1:2017 Clause 5.9.14
Sprinklers shall be arranged to prevent water from directly impinging on the surface of deep fat fryers. Where this is accomplished by the provision of a shield or baffle it shall be located so that it will not interfere with the sprinkler discharge to the areas required to be protected.

In simple terms, installers must install fire sprinkler heads within kitchen hoods but must do so such that they do not create an new or exacerbate an existing fire from hot oil.

To achieve this, the Standard says this can be accomplished by provision (installation) of a shield or baffle, and this shield or baffle must be installed such that it will not interfere with the sprinkler discharge to the areas required to be protected.

Food health & safety

The Standard also covers the requirements for food health & safety offering guidance notes for installers as follows;

As far as practicable, piping should not be exposed under cooking equipment hoods, and care should be taken to comply with the requirements of the local health authority.

In most cases, this means the following;

  • fire sprinkler piping (as far as practicable) should be concealed within the kitchen hood.  This is to eliminate the risk from the accumulation of contamination and effect of subsequent cleaning; and
  • fire sprinkler heads should be installed such that are protected from damage or accidental operation. In this case, sprinkler heads may need to be installed with a protective cage;
  • many health authorities also require fire sprinkler heads and pipes in the vicinity of a kitchen hood may also require to be manufactured from stainless steel;
  • thread seal tape (also known pink PTFE tape) is the preferable method of sealing threaded components.

Maintenance of fire sprinkler heads in kitchen hoods and ducts

AS1851:2012 Front Cover

Australian Standard AS1851 sets out the requirements for the routine servicing (including yearly inspection) of automatic fire sprinkler heads in kitchen hoods and ducts as follows;

Table 2.4.2.3
Yearly Routine Service Schedule
Automatic Fire Sprinkler Systems (Wet Pipe Systems)

Item No. Item Action required and pass/fail requirement
3.14 Kitchen hoods and ducts INSPECT all sprinklers inside kitchen hoods and ducts and CLEAN if necessary to remove accumulated grease and any other foreign matter and verify that the sprinkler head is appropriate for this application.

The most common fire sprinkler heads defect that are identified in kitchen hoods and ducts is the excessive accumulation of kitchen waste, oil and debris.

Another common defect are faulty or missing sprinkler head protective cages. 

Its is also very common to see corrosion from automatic fire sprinkler heads that are not made from stainless steel.  In these cases the sprinkler heads and other components must be replaced.

If you are responsible for a commercial kitchen with fire sprinkler heads fitted and you observe any of the defects and excessive accumulation of grease or debris around your fire sprinkler heads, then ask us for a free quotation.