Kitchen Grease Extraction System Cleaning

The kitchen extract system presents particular hazards due to the potential for the accumulation of grease. Accumulated grease within an extract system forms a hidden combustion load. Under certain circumstances flame or very high temperature within the duct can ignite the grease causing fire to spread rapidly through the duct.

The Health & Safety Executive and industry and insurance guidance and regulations stipulate that kitchen extract systems should be kept clean to minimise fire and other risks. Your insurers and the environmental health officer will expect you to risk assess and undertake routine and regular inspections and cleaning.

Review of Fire Safety Arrangements – Article 11 of The Regulatory Reform (Fire Safety) Order (RRFSO)  (England and  Wales) , the Fire (Scotland) Act 2005 and Fire Safety (Scotland) Regulations 2006,  and the Fire and Rescue Services (Northern Ireland) Order 2006 and Fire Safety  Regulations (Northern Ireland) 2010 require monitoring and review of fire safety   arrangements, the management teams of client and contractor shall  therefore conduct regular review meetings to ensure that the cleaning frequencies are sufficient to adequately control the grease levels in line  with this specification and to adjust frequencies as and when required, thus maintaining suitable fire  safety.

The B&ES document TR/19 Third Edition 2019 guidelines ‘Cleanliness of Ventilation Systems’ provides specific guidance on methods of measuring and defining cleanliness as a benchmark for good practice.  The frequency of cleaning should be adjusted by means of system testing (inspection and monitoring) so that surface grease deposit limits are not exceeded. The buildings insurance company should be consulted to ensure that the cleaning regime is compliant with the terms of their specific warranty. Any cleaning regime should be justified by a considered risk assessment. (The latest Fire Precautions Workplace and Management of Health & Safety at Work Regulations apply).


BESA TR19® Grease – Fire Risk Management of Grease Accumulation within Kitchen Extraction Systems

  • Unless recommended otherwise in a fire risk assessment undertaken by the client’s responsible person, all operational grease extract ductwork systems will usually require cleaning annually as a minimum.
  • Specific cleaning intervals stated by landlords, system designers or insurers should be identified by the owner/operator and notified to the cleaning and maintenance contractor.
  • Conditions and warranties within commercial liability/property insurance policies, should stipulate minimum cleaning frequencies for grease extract ductwork systems. However, some insurance contracts may require a higher frequency of cleaning than recommended in TR19®. Failure to comply with such requirements may invalidate the property insurance policy.
  • The frequency of cleaning should be sufficient to ensure that grease deposit limits of 200µm, as a mean across the system, are not exceeded.
  • All cleaning frequencies should be based upon accurate historical levels of grease accumulation to maintain grease deposit levels below 200 microns as a mean across the system.
  • In certain cases, sections of ducting may accumulate grease levels over 500 microns, often referred to as ‘hot spots’ or ‘high points’. Such areas should be cleaned urgently with the caveat that the extent of fouling at 500 microns and the level of risk posed should be considered. For example, 500 microns within the canopy plenum, immediately above the heat source would be a far higher risk than a small high point on a turning vane many meters away from the heat source. Interim cleaning of such high point areas should be introduced to the full system cleaning schedule where it is agreed that this is required to control the risk of high point grease level accumulation.
  • In the absence of data for historic grease deposit levels, such as a newly installed systems, time-and-usage-based methods can be used to estimate required initial cleaning frequency (see Table 4). Pre-cleaning micron readings and time periods between cleaning should be taken to accurately determine ongoing cleaning frequency so that grease levels are maintained below 200 microns as a mean across the system.

Table 4 will assist in establishing the initial cleaning frequency for the system in the absence of data on the historical pre-clean grease thickness levels and duration of days between each set of grease thickness readings

Notes to Table 4

  1. The canopy and extract plenum are areas with a high risk of fire. Consideration should be given to more frequent cleaning in accordance with insurers’ requirements.
  2. In addition to the scheduled specialist cleaning, a daily or weekly cleaning regime should be implemented on canopies, separators and associated drains and traps in accordance with manufacturers’ recommendations. Typically, these are be carried out by the kitchen operator to comply with the property insurers’ requirements.

Predictive Accumulation Assessment Table:

In order to quickly assist in selection of the correct cleaning intervals Table 5 assesses the required cleaning intervals against average grease accumulation that has built up over a number of days.

Notes to Table 5

  1. The frequency guidance table requires a simple calculation to define daily rate of accumulation in microns.
  2. To calculate daily rate take mean pre-clean system micron levels and divide by number of days since previous clean or opening of site and grease production.
  3. Select appropriate range to define the frequency of the risk control clean required to ensure micron levels do not exceed 200 as a mean between each cleaning visit.
  4. It should be noted that cleaning frequencies shown in Table 5 are indicative only and are based on historic usage of the system. They should not be seen as substitute to an actual cleanliness risk assessment undertaken by a competent person. When calculating the cleaning frequency seasonal variations and changes in the type and frequency of cooking should be taken into consideration. An additional risk assessment may be required as a result.

Examples of cleaning methods used, to attain the specified level of hygiene are found in Table 2

Note to Table 2

The techniques employed will be based upon the system type, accessibility, and level of contamination. The cleaning methods listed are considered as best practice. The list is not exhaustive and new technology is being introduced regularly. Therefore, it is critical that the cleanliness result of any method used shall meet the requirements of the post-clean verification.

Post Clean Reports & Certification

  1. An executive summary page that highlights the following key risks:
    • A clear statement (yes or no) indicating whether or not the system was cleaned in its entirety.
    • If no to the above question, state precisely what wasn’t cleaned and why not together with suggested solutions and recommendations.
    • A recommendation of a new cleaning frequency based on the pre-clean Grease Thickness Test readings. In order to calculate a frequency based on keeping grease levels below 200 microns as a mean across the system, the rate of build-up of grease needs to be assumed to be linear over time and therefore the recommended new frequency can be calculated using Table 5 and the guidance in the notes to the predictive accumulation assessment table.
  2. Micron readings for the stipulated test locations. The mean (average) micron reading across all micron readings taken.
  3. Other hazards that have been identified.
  4. Pre agreement with a client of a specific section or area that is not to be cleaned.
  5. A sufficient number of photographs of the system taken before and after cleaning that are representative of the system condition. These should be as per system testing and more if the duct length exceeds 10m. (See Clause 6.4)
  6. A schematic diagram or, as-installed drawing of the system layout showing the system in its entirety including known components, changes of direction, access panels, areas that have been cleaned and any areas that could not be cleaned.

Our post clean reports will be registered on the BESCA VHE scheme, or equivalent recognised scheme, in order to be compliant with TR19®.