Commercial kitchen extract cleaning concerns a grease-conveying system that begins above the cooking appliances and continues to the final discharge point. It is a separate discipline from cleaning comfort-ventilation ductwork because the contaminant, system construction, access arrangements, cleaning techniques and fire implications are different.
A commercial kitchen extract system normally starts with the canopy or hood positioned above the cooking line. The canopy captures rising heat, steam, smoke, airborne grease and other cooking effluent, while removable grease filters intercept part of the grease before the air enters the internal plenum behind or above them. From the plenum, the extract passes into branch ductwork or a main duct, through horizontal sections, bends and vertical risers, then through or towards an extract fan before being discharged outside.
Every part of that route affects the cleaning task. The visible canopy may be easy to inspect and may receive regular surface cleaning, but it represents only the beginning of the system. The plenum, filter seating channels, transitions, fan casing, fan blades, discharge duct and weather termination can all retain grease. ASHRAE material treats commercial kitchen ventilation as a distinct technical subject, while its published terminology describes a hood as an assembly intended to contain and remove airborne grease, combustion products, smoke, odours, heat and steam.
Cooking produces an aerosol and vapour mixture containing oils, fats, moisture and fine particles. As that mixture travels away from the hotter cooking zone and meets cooler metal surfaces, part of it condenses or impinges on the duct wall. The resulting contamination can range from a soft oily film to a thick tacky layer or a harder, carbonised deposit, depending on cooking method, temperature, maintenance history and the location within the system.
This behaviour is unlike the mainly dry particulate found in many comfort-air systems. Grease can smear, run, pool, bind other particles and resist ordinary brushing. It may also soften when heated and spread across surfaces during cleaning unless loosened material and wash water are properly contained. Solvents or alkaline degreasers may be useful in some circumstances, but their selection has to account for the duct material, seals, coatings, food-area controls, waste handling and the possibility of residues.
Comfort-ventilation duct cleaning is addressed elsewhere on the site and should not be treated as an interchangeable method statement for grease extract work.
A clean-looking canopy does not demonstrate that the internal duct is clean. Filters remove only part of the grease carried by the airflow, and their performance depends on type, condition, fit and cleaning. Grease that passes the filters may deposit progressively along the route or accumulate at particular features where airflow changes direction, velocity or temperature.
Important areas include the rear of filters, canopy corners, plenums, low points, horizontal ledges, bends, transitions, fan housings and the section immediately before or after the fan. A roof-mounted fan can contain substantial contamination even when the lower canopy has been maintained. The discharge arrangement also matters because deposits may remain on the fan outlet, cowl, louvre or nearby surface.
A scope limited to "hood cleaning" can therefore describe a much smaller task than full kitchen extract cleaning. The wording should identify whether filters, canopy, plenum, all accessible ductwork, risers, fan, discharge section and external termination are included. Any part excluded because of isolation, access, construction or safety constraints should be stated before work begins and recorded afterwards.
Internal cleaning depends on physical access to the grease-contaminated surfaces. Existing panels may be too small, badly positioned, sealed behind finishes or blocked by services. Some systems have long runs with very few openings, while others pass through ceiling voids, shafts, plant rooms, roof spaces or occupied areas where access requires separate planning.
A concealed vertical riser is a common practical problem. Cleaning tools introduced from the bottom or top may not reach every surface, bend or offset, and loosened grease can fall to an inaccessible base. A riser inside a fire-resisting shaft may have inspection openings in the duct but no usable route through the enclosure. Decorative ceilings, fixed joinery or tenancy boundaries can further restrict the work.
Access panels should be suitable for the duct construction and should be positioned where they permit inspection, cleaning and verification, not merely where installation was convenient. Their covers, frames and fastenings should remain secure after repeated opening. Where a grease duct has been designed as a liquid-tight system, cleaning and access work should preserve that characteristic; ASHRAE Standard 154 material specifically addresses liquid-tight grease duct construction and testing.
Dry brushing and vacuum collection can be effective for loose dry debris, but a grease system often needs scraping, mechanical agitation, controlled chemical application, steam or pressure washing, or a combination of methods. The chosen technique depends on deposit consistency, duct material, access, drainage, electrical equipment and the ability to contain liquids and loosened contamination.
Mechanical scraping may be needed for thick or carbonised deposits. Chemical degreasing can soften films but requires controlled dwell time and complete removal. Pressure washing may clean large accessible surfaces efficiently, yet it introduces water that can escape through defective seams, enter electrical equipment, migrate into occupied areas or collect in hidden low points. Fan motors, controls, fire-suppression components and nearby appliances may need protection or isolation.
The objective is not simply to pass equipment through the duct. The method should remove deposits from the internal surfaces without spreading contamination, damaging the system or leaving a new hazard behind. Waste grease, contaminated wash water, disposable sheeting and used absorbents should be contained and removed through an agreed route.
Kitchen extract work can combine several hazards in one task. Roof access may involve ladders, fragile surfaces, unprotected edges or work beside a rotating fan. Internal entry into a large duct or plenum may create confined-space concerns where access, ventilation, rescue or isolation is inadequate. Electrical supplies, automatic controls and fire-suppression equipment may need to be made safe before work starts.
Cleaning teams may also encounter sharp sheet-metal edges, unstable access panels, hot surfaces, chemicals and heavy grease released overhead. Work in a live food premises requires separation from food preparation and control of contamination. Where a new access opening is cut or welded, the activity should be planned as hot work, with the surrounding grease condition, combustible materials, fire precautions and post-work checks considered before the task begins.
Competence therefore includes system recognition, cleaning technique, isolation, work at height, chemical handling, contamination control and the ability to stop when access or conditions make the planned method unsafe. A person who can clean a visible canopy is not automatically competent to assess and clean a concealed multi-storey grease duct.
A suitable scope starts by identifying the system and its route. It should name the canopy, filter bank, plenum, branches, main duct, horizontal sections, vertical riser, fan, discharge duct and termination where present. It should state the approximate route, known access panels, expected isolation arrangements, working areas, required protection and whether new access will be needed.
The scope should also define the cleaning outcome and the evidence expected. Representative before-and-after photographs should be linked to named locations rather than supplied as unidentified close-ups. The completion record should show which sections were reached, which were not reached, the reason for any restriction, the condition of the fan and discharge, and any defect that prevented effective cleaning.
No primary document could be produced establishing a kitchen extract contractor approval scheme in any emirate or a legally set cleaning interval anywhere in the UAE. Dubai Municipality publishes its Indoor Air Quality for Healthy Life document as technical guidance rather than a binding standard, and it does not establish a kitchen grease-extract cleaning rule.
Kitchen extract removes a process emission rather than conditioning a space, which puts it closer to the family of systems described in an introduction to local exhaust ventilation as engineering plant.
No primary document could be produced establishing a kitchen extract contractor approval scheme in any emirate or a legally set cleaning interval anywhere in the UAE. Dubai Municipality publishes its Indoor Air Quality for Healthy Life document as technical guidance rather than a binding standard, and it does not establish a kitchen grease-extract cleaning rule.
Any part excluded because of isolation, access, construction or safety constraints should be stated before work begins and recorded afterwards. A partial result should not be described in language that implies complete coverage.
No. The canopy is only the visible capture point, while the extract system continues through filters, the plenum, ductwork, risers, the fan and the discharge arrangement. A completion record should make clear which of those parts were included.
A vertical riser may be concealed inside a shaft, offset between floors or accessible only from one end. Effective cleaning may require properly positioned access panels and a safe means of collecting material released from the duct walls.
Some mechanical tools may form part of the method, but dry brushing alone may not remove tacky or carbonised grease. The equipment and process should be selected for the actual deposit and should control loosened grease, liquids and chemical residues.
The fan should be explicitly included or excluded in the scope. Grease can collect on blades, inside the casing and around the discharge, affecting cleanliness, balance and the continuity of the cleaned route.
The inaccessible section should be identified by location, with the reason and its likely extent recorded. The record should recommend a practical remedy, such as improved access, alteration of an enclosure or a separate planned intervention, rather than presenting a partial clean as complete.