Ductwork cleaning is booming

« Back to blog home15 Sep 2016 by Indepth Hygiene

Ventilation hygiene is enjoying a period of sustained growth because its role in fire prevention is now more widely understood, according to BESA Ventilation Hygiene Working Group chairman Richard Norman*.

Commercial kitchen extract ventilation systems are being cleaned with greater regularity than ever before. Better and more regular fire risk assessments and improved understanding of the danger posed by poorly maintained extract systems means more commercial kitchen operators are taking this issue seriously.

The demand for professional ventilation hygiene services is at an all-time high and clients are shortening the periods in between cleaning visits. In some very busy commercial kitchens, the grease extract ventilation is being cleaned every two weeks.

However, while the level of professionalism across the industry is also improving, too many cleans are still not being carried out properly. Every ventilation hygiene company should be asking: Does my work comply with industry best practice? Is the system fully clean? Are clients being provided with compliant work supported by proper post-clean reports?

Anything less is dishonest because it is taking money under false pretences and immoral because an incomplete extract clean leaves building occupants exposed to greater fire risk.


Post-clean reports are becoming increasingly sophisticated and should all include system schematics and photographs to clearly show clients the pre and post-clean condition of their system. The availability of wearable technologies and digital cameras means full and detailed system assessments are easy to do.

Over half of all fires attended by fire fighters in the UK involve cooking equipment in restaurants, canteens, hotel kitchens and fast food outlets. The potential for accidents in these fast paced, highly pressurised environments involving flammable cooking oil, naked flames and heat sources is clear. As a result, this is an area of high priority for insurance companies.

According to a study by the fire and security organisation IFSEC, around a quarter of the estimated 24,000 accidental fires in non-domestic buildings each year are caused by cooking appliances. Commercial kitchens are at the highest risk and local authority environmental health officers are also becoming increasingly aware of the need to seek help from specialist building services maintenance firms to reduce fire risks.

Extract systems in kitchens can be a source of high fire risk if they are not kept clear of grease and other residues. According to the London Fire Brigade, there are 10 serious fires in the capital every week started by kitchen appliances and, in a large number; the damage is made more serious because the fire spreads to other parts of the building through dirty ventilation ductwork.

Since the introduction of the Regulatory Reform (Fire Safety) Order (RRO) 10 years ago, building owners and managers have faced far more stringent requirements to carry out fire risk assessments and manage those risks effectively.

As a result, ductwork cleaning has become a much more dynamic process with regular reviews of cleaning programmes and regular monitoring of contamination levels particularly in very busy kitchens. After every clean, part of the reporting process should be to review the frequency of cleans – up or down – to make sure the process meets the safety requirements cost-effectively; and takes the type of cooking and its associated risks into account.

The average contamination threshold across the system that should trigger a clean is 200 microns of accumulated grease or dirt deposits. It is important, therefore, that systems are regularly checked and the build-up of contaminants measured. Most professional ventilation hygiene firms will offer to evaluate the system and make a recommendation about the frequency of cleaning. It is up to the client whether they accept this advice, but it should be taken into account in any fire risk assessment – and insurers are increasingly interested in this kind of technical detail.

Most commercial kitchens insist that their contractors meet the standards imposed by the ventilation hygiene industry’s Guide to Good Practice: ‘Internal Cleanliness of Ventilation Systems’ (TR/19), which is published and updated by the Building Engineering Services Association (BESA).


Since it first appeared in 1998, TR/19 has been widely accepted within the building engineering services sector and by insurers as the standard to which ventilation systems should be cleaned – it was thoroughly revised and updated in 2013.

The updated TR/19 (2

nd edition) provides clarity about when and to what standard grease extract systems should be cleaned, and provides a detailed explanation (in the absence of micron measurements) of the frequency of cleaning required based on the type of cooking and the hours of kitchen usage. Having an accurate micron measurement is the best method for establishing a cleaning regime tailored to the establishment in question and this can be established after an initial clean and then a follow up visit to monitor how quickly grease is building up.

This will also help building owners to meet their obligations under the Regulatory Reform (fire safety) Order 2005 and stay on the right side of fire officers who have the power to close down a building if they are not satisfied that the extract systems are safe.

It is also absolutely not acceptable to use wording such as: "All accessible areas were cleaned" in post-clean reports. This is not compliant with TR/19. It might be that no part of the system is ‘accessible’ in the strictest sense of the word and there are some disreputable firms, who are providing only superficial cleaning (and sometimes no cleaning at all), but trying to claim their activities are compliant with TR/19.

To comply with the RRO and TR/19, a post-clean report should include an executive summary page that highlights the key risks along with a full system schematic and photographs showing the condition of the duct before and after cleaning.

The report must also provide a clear ‘yes’ or ‘no’ as to whether the system was cleaned in its entirety. If the answer is ‘no, then a reason must be given and a solution suggested.

The report should also include other hazards that have been identified and micron readings for the parts of the system tested leading to a mean (average) micron reading for the complete system. The current cleaning frequency should also be recorded and if the hygiene company believes a higher frequency of cleaning is needed, based on the micron readings, then that should be clearly indicated to the end client.

According to TR/19, if an area is not accessible you have to make it accessible by fitting access panels or using equipment that can reach into all areas. If this is really not possible, then you have to clearly explain this to the client and provide a suggested course of remedial action. The post-clean report should contain a schematic that clearly shows where the system has been cleaned and where not – with reasons.

The good news is that we are seeing more compliant cleans being carried out since action on accessibility was clarified by BESA this year. Many organisations, including some major hotel and restaurant chains, are now addressing the poor standard of ventilation hygiene service they had been receiving and, as a result, the risk of fire in these premises is falling significantly.

*Richard Norman is managing director of Indepth Hygiene.

Copies of TR19 Edition 2 (2013) can be purchased online at: www.theBESA.com.