Grease duct
Encyclopedia
A grease duct is a duct
that is specifically designed to vent grease
-laden vapor
s from commercial cooking equipment such as stove
s, pizza
oven
s, deep fryers and wok
s to the outside of a building or mobile food preparation trailer. Grease ducts are regulated both in terms of their construction and maintenance, forming part of the building's passive fire protection
system
. Even the cleaning schedule is typically dictated by the fire code and evidence of compliance must be kept on file by the owner.
as well as compliance with local fire codes to vent such vapours outside the kitchen and outside the building where the kitchen is located.
Grease, of course, is not only slippery, but also highly flammable. In fact, it qualifies as a hydrocarbon
due to its inherent chemistry
. Regardless of what state
it is in, vapour, liquid or solid, it ignites easily and burns very rapidly, necessitating special provisions to accomplish a fire-resistance rating
based on an internal grease fire as well as an external fire. Special provisions also include the necessity for proof that any adjacent firestop
must be compatible with the grease duct system.
96 as well as the local building code
s and fire codes. Cleaning takes place typically every 3 months, 6 months or annually, depending on the nature of the appliances below the hood. For instance, woks require quarterly grease duct cleaning, whereas normal stoves may necessitate the grease duct to be cleaned only every 6 months. Compliance must be proven through certificates issued by the cleaning and maintenance contractors. Purpose-designed fire suppression systems inside the hoods must also be routinely maintained. Proper cleaning must be enabled through the use of approved, fire-resistant access panels. Grease ducts should be kept as short as possible to minimise grease build-up.
, all welded
, per local codes, which is then externally treated with fireproofing
. Typical materials used for fireproofing are:
construction
sites, metallic ducts are typically installed by the sheet metal trade, whereas external wraps are usually installed by the insulators. Inherently fire-resistant systems are likewise installed by the sheet metal trade.
Duct (HVAC)
Ducts are used in heating, ventilation, and air conditioning to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air. Ducts also deliver, most commonly as part of the supply air, ventilation air...
that is specifically designed to vent grease
Vegetable fats and oils
Vegetable fats and oils are lipid materials derived from plants. Physically, oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides, as contrasted with waxes which lack glycerin in their structure...
-laden vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....
s from commercial cooking equipment such as stove
Stove
A stove is an enclosed heated space. The term is commonly taken to mean an enclosed space in which fuel is burned to provide heating, either to heat the space in which the stove is situated or to heat the stove itself, and items placed on it...
s, pizza
Pizza
Pizza is an oven-baked, flat, disc-shaped bread typically topped with a tomato sauce, cheese and various toppings.Originating in Italy, from the Neapolitan cuisine, the dish has become popular in many parts of the world. An establishment that makes and sells pizzas is called a "pizzeria"...
oven
Oven
An oven is a thermally insulated chamber used for the heating, baking or drying of a substance. It is most commonly used for cooking. Kilns, and furnaces are special-purpose ovens...
s, deep fryers and wok
Wok
A wok is a versatile round-bottomed cooking vessel originating in China. It is used especially in East and Southeast Asia.Woks are most often used for stir frying, but can also be used in other Chinese cooking techniques, such as in steaming, deep frying, braising, stewing, smoking, or making soup...
s to the outside of a building or mobile food preparation trailer. Grease ducts are regulated both in terms of their construction and maintenance, forming part of the building's passive fire protection
Passive fire protection
Passive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors...
system
System
System is a set of interacting or interdependent components forming an integrated whole....
. Even the cleaning schedule is typically dictated by the fire code and evidence of compliance must be kept on file by the owner.
Special hazard
The grease laden vapors are hot, to begin with. As the vapours cool down, the grease settles on colder items. It is thus important for occupational safety and healthOccupational safety and health
Occupational safety and health is a cross-disciplinary area concerned with protecting the safety, health and welfare of people engaged in work or employment. The goal of all occupational safety and health programs is to foster a safe work environment...
as well as compliance with local fire codes to vent such vapours outside the kitchen and outside the building where the kitchen is located.
Grease, of course, is not only slippery, but also highly flammable. In fact, it qualifies as a hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
due to its inherent chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
. Regardless of what state
State of matter
States of matter are the distinct forms that different phases of matter take on. Solid, liquid and gas are the most common states of matter on Earth. However, much of the baryonic matter of the universe is in the form of hot plasma, both as rarefied interstellar medium and as dense...
it is in, vapour, liquid or solid, it ignites easily and burns very rapidly, necessitating special provisions to accomplish a fire-resistance rating
Fire-resistance rating
A fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test. This can be quantified simply as a measure of time, or it may entail a host of other criteria, involving other evidence of functionality or fitness for...
based on an internal grease fire as well as an external fire. Special provisions also include the necessity for proof that any adjacent firestop
Firestop
A firestop is a passive fire protection system of various components used to seal openings and joints in fire-resistance rated wall and/or floor assemblies, based on fire testing and certification listings....
must be compatible with the grease duct system.
Requirements
In North America, grease ducts must be in compliance with NFPANational Fire Protection Association
The National Fire Protection Association is a United States trade association that creates and maintains private, copywrited, standards and codes for usage and adoption by local governments...
96 as well as the local building code
Building code
A building code, or building control, is a set of rules that specify the minimum acceptable level of safety for constructed objects such as buildings and nonbuilding structures. The main purpose of building codes are to protect public health, safety and general welfare as they relate to the...
s and fire codes. Cleaning takes place typically every 3 months, 6 months or annually, depending on the nature of the appliances below the hood. For instance, woks require quarterly grease duct cleaning, whereas normal stoves may necessitate the grease duct to be cleaned only every 6 months. Compliance must be proven through certificates issued by the cleaning and maintenance contractors. Purpose-designed fire suppression systems inside the hoods must also be routinely maintained. Proper cleaning must be enabled through the use of approved, fire-resistant access panels. Grease ducts should be kept as short as possible to minimise grease build-up.
Systems
A proprietary duct system that has its own inherent fire-resistance rating can be used, or a metallic duct, typically from 16 gauge sheet metalSheet metal
Sheet metal is simply metal formed into thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of different shapes. Countless everyday objects are constructed of the material...
, all welded
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
, per local codes, which is then externally treated with fireproofing
Fireproofing
Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
. Typical materials used for fireproofing are:
- ceramic fibres
- rockwool
- calcium silicateCalcium silicateCalcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and sometimes formulated 2CaO.SiO2. It is one of group of compounds obtained by reacting calcium oxide and silica in various ratios e.g. 3CaO.SiO2, Ca3SiO5; 2CaO.SiO2, Ca2SiO4; 3CaO.2SiO2, Ca3Si2O7 and...
- vermiculiteVermiculiteVermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite...
boards pressed and bonded with sodium silicateSodium silicateSodium silicate is the common name for a compound sodium metasilicate, Na2SiO3, also known as water glass or liquid glass. It is available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and automobiles... - intumescentIntumescentAn intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection and, in America, require listing and approval use and compliance in their installed configurations in order to...
s - endothermicEndothermicIn thermodynamics, the word endothermic describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the prefix endo- and the Greek word thermasi,...
materials, sometimes on their own, sometimes in combination with ceramic fibre
Trade jurisdiction
In North American unionisedTrade union
A trade union, trades union or labor union is an organization of workers that have banded together to achieve common goals such as better working conditions. The trade union, through its leadership, bargains with the employer on behalf of union members and negotiates labour contracts with...
construction
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
sites, metallic ducts are typically installed by the sheet metal trade, whereas external wraps are usually installed by the insulators. Inherently fire-resistant systems are likewise installed by the sheet metal trade.
See also
- Passive fire protectionPassive fire protectionPassive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors...
- Duct (HVAC)Duct (HVAC)Ducts are used in heating, ventilation, and air conditioning to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air. Ducts also deliver, most commonly as part of the supply air, ventilation air...
- Pressurisation ductworkPressurisation ductworkPressurisation ductwork is a passive fire protection system. It is used to supply a steady stream of fresh air to any area of refuge or designated emergency evacuation or egress route.-Purpose:...
- Smoke exhaust ductworkSmoke exhaust ductworkSmoke Exhaust Ductwork is typically protected via passive fire protection means, subject to fire testing and listing and approval use and compliance. It is used to remove smoke from buildings, ships or offshore structures to enable emergency evacuation as well as improved firefighting.-Means of...
- Circuit integrityCircuit integrityCircuit integrity refers to the operability of electrical circuits during a fire. It is a form of fire-resistance rating. Circuit integrity is achieved via passive fire protection means, which are subject to stringent listing and approval use and compliance.-Fireproofing:Providing fireproofing for...
- Kitchen exhaust cleaningKitchen exhaust cleaningKitchen exhaust cleaning is the process of removing grease that has accumulated inside the ducts, hoods, fans and vents of exhaust systems of commercial kitchens. Left uncleaned, kitchen exhaust systems eventually accumulate enough grease to become extreme fire hazards...
- Extractor hoodExtractor hoodAn extractor hood is a device containing a mechanical fan that hangs above the stove or cooktop in the kitchen. It removes airborne grease, combustion products, smoke, odors, heat, and steam from the air by a combination of filtration and evacuation of the air.-Name:The device is known as an...