Heating and Ventilating

It is essential to look ahead to how ductwork will be cleaned and maintained when designing and installing each system. Gary Nicholls explains why.
In an increasingly litigious society and with a growing number of regulations to which building managers must adhere, the behind the scenes expert cleaning of ventilation ductwork has rarely been more important. Not only can the victims of fires and their families take out civil actions against the owners of a commercial building should the worst happen; the responsible person - a legal term under fire regulations - can also be liable to criminal prosecution.

This is quite apart from the cost of fires in commercial kitchens. According to statistics from the Association of British Insurers, around £65m is paid out as a result of kitchen fires in commercial settings each year. However, in cases where the insurers deem that there has not been effective cleaning of kitchen extract ductwork and grease deposits are partly to blame, particularly for the spread of a fire, they frequently refuse to pay out, so that the cost of the fire falls on the building owner or its lessee.

With the increase of the open plan office, in particular with the rise of the call centre and its like, a healthy indoor atmosphere is essential for preventing the spread of illness and the loss of excessive numbers of working days to staff absence. Stale air also creates lethargy and decreases productivity. Cleaning ventilation ductwork in order to provide good quality indoor air is governed by Health & Safety requirements and is a legal obligation. Regularly cleaning ductwork also makes sound business sense as good air quality increases productivity and reduces absence.

Whether it's a question of maintaining a healthy ventilation system or fire prevention, cleaning ductwork at regular intervals isn't simply a case of cleanliness being desirable, it's critical in terms of preventing harm coming to the end users of a building and protecting the responsible person from prosecution. This means that cleaning must be regular, effective and thorough and by considering this at the outset, the m&e contractor can help.

Accessibility of ductwork
In part, how effectively a system can be cleaned will depend on how accessible the ductwork is to the cleaning operative. Most systems can be cleaned effectively, but the design and installation of some systems in the past have made it more difficult to clean thoroughly in every area. Some parts of the kitchen extract ventilation in commercial kitchens, for example, not only make it more difficult to clean, they also encourage the formation of the greasy and oily deposits which we would wish to eliminate.

There are a few considerations to bear in mind when designing ventilation ductwork which can help to ensure that regular effective cleaning can be carried out. The first issue to consider is access. As specialist cleaners we often find that existing ventilation systems which have been in place for some time were not installed with access in mind. Effective cleaning can and often does mean the operative actually entering the ductwork system to clean by hand, yet many older systems have no access points which allow this.

Of course, access points can be added at a later stage; we often find that we need to cut into ductwork and install an access door which will allow operatives to enter at regular intervals in the future. However, it is far better to assess what access will be required at the time of design and installation in order to make life easier for those who will maintain in on an ongoing basis.

Taking advice is a wise move
Taking advice from the specialist cleaning company that will carry out the regular cleaning is a wise move, as they will be able to explain the challenges of this from the cleaning operative's practical and experienced point of view.

Access doors should be installed at key locations such as bends and turns in the duckwork as these will be areas at which oil and grease are more likely to accumulate in the case of kitchen extract systems. Retrofitting them can be more disruptive to the fabric of the building than tackling this at the time of initial construction. The presence of an access door also serves as a handy reminder to building managers that regular cleaning must be carried out. It also affords the building manager a vital porthole through which to inspect the cleaning company's work.

The design of the ductwork is clearly also key; avoiding bends, twists and turns in the route over which the ductwork travels is essential. A right angle will often mean that hot or even warm air will come into contact with a colder surface at a right angle for example, and this rapid cooling of the air stream will result in it depositing more of the airborne fat, oil or water than if it had been allowed to carry on unimpeded.

However, from a practical perspective, any right angles or sharp bends which are necessary are also a key location for an access point to facilitate easier cleaning.

The regulations governing the cleaning of ventilation ductwork and fire prevention in kitchen extract ductwork require vigilance and adherence to a prescribed cleaning schedule.

Section 7 of TR/19 is recognised as the leading guidance document for controlling fire risk in kitchen extract systems. It currently suggests that kitchen extract systems in heavy use - 12 to 16 hours a day - should be cleaned at least quarterly. Those in moderate use - 6 to 12 hours a day - should be cleaned half-yearly. Finally, those in light use - two to six hours a day - should be cleaned at least once a year. TR/19 is under review by a B&ES technical committee, on which I currently sit.

The ductwork system should take the frequency with which it will need to be cleaned into consideration. Ideally it will take the shortest possible route to the outside of a building, using straight runs where possible. If possible, it is also best to avoid passing ductwork serving a kitchen through living accommodation or public areas to avoid the risk of the spread of any fire from the kitchen to other, particularly densely populated parts of the building.

Talking to the experts who will keep a system clean and compliant in the future is a wise move when planning it.

// The author is managing director of Swiftclean //