Clearing the air on ventilation hygiene

View through duct
Before the involvement of BESA and the guidance it has issued over the years, engineers would often find dirt and debris from the installation process present in working ventilation systems.

Gary Nicholls, Managing Director of duct cleaning expert Swiftclean, and co-author of TR19®, looks at the long-anticipated TR19® Air specification and what this may mean for ventilation hygiene standards.

With awareness surrounding the importance of the impact of indoor air quality on occupants’ health and wellbeing has increased, a greater emphasis is also being placed on ventilation system hygiene.

Not only is this sharper focus welcome, but it is set to raise standards in the industry, as TR19® Air will provide a clear specification to guide property and facilities managers towards consistent best practice and compliance.

Thankfully, the days when ventilation systems could be handed over without being cleaned in readiness for use are long gone. The development over the years of first TR17 then TR19, issued by BESA (Building Engineering Services Association) has gone a long way towards ensuring that buildings are served by clean, well-commissioned ventilation systems, which transport air free of contaminants to the property’s occupants.

Before the involvement of BESA and the guidance it has issued over the years, we would often find dirt and debris from the installation process present in working ventilation systems.

TR19 (and its predecessor TR17) was drafted as the leading guidance document on ventilation hygiene to tackle the twin challenges of fire safety and indoor air quality. In the case of kitchen extract ductwork, the chief concern is fire safety. Cooking of any genre gives rise to airborne fat oil and grease (FOG) particles which, together with water vapour and hot air from the kitchen, are carried as an exhaust stream and expelled to the exterior of the property. However, as the hot air travels further from its source, it also cools, depositing FOG particles on the inner surfaces of the ductwork. Gradually, greasy deposits form on the surfaces of the ductwork, and these are a serious potential fire hazard.

In July 2019 a new specification, TR19® Grease, was born out of section 7 of the second edition of TR19. With the status of a specification, rather than a guidance document, TR19® Grease has become the standalone requirement with which commercial kitchens must comply. This represents a large step forward in catering fire safety. It is well recognised that many fires which start in the kitchen are made significantly worse and will spread further through the building if the ductwork is not TR19® Grease compliant.

The remainder of TR19 was then reissued, without section 7, as TR19®; which then entered a period of review which will result in the issuing of the now long expected TR19® Air.

The wait is over

We did originally expect that TR19® Air would follow fairly quickly on the heels of TR19® Grease, but it was delayed. Principally, it has been delayed by a review of the Regulatory Reform (Fire Safety) Order 2005, which was somewhat inevitable following the Grenfell fire disaster and the introduction of the Building Safety Act 2022.

Although we know that in this tragic case, the fire largely travelled up the outside of the building because of the cladding, it was important to discover whether there were any further lessons to be learned from the construction and maintenance of ventilation systems. In this case, ventilation systems were not implicated in the spread of the fire, but a poorly constructed and maintained system could undoubtedly add to the risk of the spread of fire.

Inside Ductwork
Ductwork itself must also be free of dust, lint or debris which could provide fuel for a fire; or cause an irritant for those building occupants suffering from asthma or other breathing difficulties.

Ventilation ductwork must be fitted with a fire damper at the point at which the ductwork creates an opening in the fire-resistant wall. Fire dampers comprise a set of steel louvres which close automatically in the event of fire to reseal the compartment created by the fire resistant wall, helping to delay the spread of fire. It is essential, therefore, that we can access fire dampers for annual testing to ensure that they work effectively.

Ductwork itself must also be free of dust, lint or debris which could provide fuel for a fire; or cause an irritant for those building occupants suffering from asthma or other breathing difficulties.

What can we expect from TR19® Air? Without doubt, this will place an even greater importance on access. It will also, like its counterpart TR19® Grease, be a specification, rather than guidance. It will, as with the current TR19®, require building managers to classify ventilation systems as high, medium or low according to their use.

Systems servicing laboratories, cleanrooms and operating theatres, for example, will be classified as high, because they demand particularly high air quality and fine HEPA filters. Less frequented areas such as boiler rooms or plant rooms may be classified as low, while most habitable areas will have a medium classification. TR19®Air will continue to contain helpful tables which set out the intervals at which ventilation systems should be cleaned according to their classification, purpose and frequency of use. TR19® Air will become a very clear specification which building and facilities managers can follow to ensure compliance throughout the property.

In order to ensure that the ventilation system is not circulating contaminants, it is vital that we can clean its entire length and that means that we must be able to access every part of it. We therefore expect that TR19® Air will improve accessibility. It is widely expected that there will be an increased requirement for access hatches, especially where there are turns in the ductwork, or access to fire dampers is required.

This could create something of an increased tension between TR19® Air, the soon to be specification for ventilation system compliance, and DW/144: Specification for Sheet Metal Ductwork, the specification for the design and construction of metal ductwork. DW/144 does not require the same frequency of access points for the construction of ductwork as TR19® requires for its ongoing compliance. If, as we expect, TR19® Air calls for more access points at shorter intervals, the practical gap between construction standard and compliance specification will widen.

It seems wise, therefore, to call for a revision to be made to DW/144 to fall in line with the requirements of ongoing compliance. In the meantime, with regard to access for future cleaning and compliance, it would seem sensible to design ventilation systems, from an access point of view, to comply with TR19® Air, rather than DW/144. This would avoid the situation in which additional access points need to be installed, at greater cost, in order to facilitate the very first system clean.

The importance of clean ventilation systems has been more widely acknowledged in recent years, as has the importance of using an expert cleaning contractor to provide compliance. BESA recommends appointing a cleaning provider registered with the Vent Hygiene Register (VHR), which is overseen by BESA’s certification arm, BESCA. VHR members must provide fully qualified, competent technicians who are fully trained and hold BESA training qualifications in ventilation system hygiene. VHR members will also be able to provide post-clean certification through BESCA, providing the facilities manager with proof of compliance.

By bringing more clarity and emphasis on clean air, TR19® Air is set to ensure that we can all breathe more easily.

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