The risk posed by fires in ventilation systems means contractors and manufacturers must collaborate more effectively, says Kevin Munson
IN THE FIVE YEARS since the Regulatory Reform (Fire Safety) Order came into force, the pressure on building owners to carry out proper risk assessments has been intense. However, many remain completely in the dark about the role ventilation systems play in the event of a fire and a great number of buildings remain at risk as a result.
Air transfer ductwork has always presented a challenge to building designers trying to restrict the chances of a fire spreading. Fire and smoke dampers are the crucial element, but the steps needed to ensure they work effectively are often poorly understood - or simply ignored. The ductwork industry is trying to do its bit and the most professional contractors are in a position to provide detailed and targeted information about fire safety so end clients can assess their vulnerability and meet their legal obligations.
However, sloppy implementation of the Building Regulations regularly undermines the best intentions of the ductwork industry. For ductwork to perform well in a fire, a good standard of building work around the ventilation system is essential. Fire does not just pass along the ductwork; it can be outside and affect the penetration seal.
To achieve a compliant installation, the design and install team must follow a planned sequence and appoint a CDM co-ordinator to ensure good communications with all members of the project supply chain. The information must then be passed onto the end client who has ultimate responsibility (and faces the human and legal costs) if there is a fire in their building.
The crucial relationship is, however, between damper manufacturer and installer. Ductwork contractors regularly, and justifiably, complain that they are often hung out to dry by the process. They are the final link in the supply chain and so are on a hiding to nothing if the other professions do not do their jobs properly. Incomplete or inaccurate technical data supplied by the design team can make their task difficult - if not impossible. They are also usually expected to work to other people's designs, having had no input into the testing and specification of the chosen solution. Also, some damper systems perform brilliantly in laboratory conditions, but fail to come up to the mark in 'real life' situations.
This was a major motivation behind the production of the HVCA's Guide to Good Practice: Installation of Fire and Smoke Dampers (DW/145). This was spearheaded by the association's Ductwork Group and produced two years ago. Its intent has been approved by the Association of Smoke and Fire Protection (ASFP) and CIBSE - along with a wide range of other industry bodies and building insurers.
However, its recommendations have still not been widely adopted despite the fact that working to its guidelines would ensure far more installations are legally compliant. Issues that emerged during research for DW/145 included the importance of only installing dampers that have been tested in real site conditions. The guidance explains that all fire dampers should be tested according to BS EN 1366-2 and classified to BS EN 13501-3 as required by the Building Regulations. Air tightness and leakage rates should be evaluated according to Section 10 of BS EN 1366-2.
The testing is only meaningful if it represents 'real' conditions to show how the dampers perform in various types of wall or floor installations and when subjected to different pressures through the ventilation system. Damper manufacturers should be able to provide bespoke information for contractors and their clients to aid in decision making. They must also provide dimensionally detailed guidance on how the damper assembly is to be installed including any requirements for damper unit expansion.
Only tested dampers should be used and the installer must check on the stability of the dry lining partition to ensure the damper can continue to do its job in a fire. Also, many dampers are sold without a fixing arrangement.
Manufacturers' installation documents should provide contractors with detailed pathways towards compliant installations and they should link the guidance to product specific literature to help with decision making.
Professional damper installers also work to a comprehensive checklist that is signed off at the end of the job and manufacturers have a responsibility to make sure they help in establishing those checklists. The manufacturer should also co-operate to ensure their specified approach is practical on site and this might require input from a specialist fire safety engineer at design stage.
Fire strategy drawings produced by the design team should be specific to the project in hand and clearly indicate fire and smoke compartmentation, as well as the type and classification of the fire barrier and its construction. Manufacturers should be able to provide additional, specific guidance at all stages of the design process, as well as being available right up until the project is signed off to help the contractor with any problems they encounter on site.
A regular difficulty is that service penetrations are designated long before contractors are even on site, so are often either inconveniently positioned or simply impractical for the installation especially if multi-service openings are envisaged. Again manufacturers can play a role in supporting consulting engineers with specialist knowledge to minimise this type of problem occurring in the early stages of the programme.
The project team should aim for penetrations being formed 'as tested' with the damper assemblies coming complete with the fixing arrangement. All trades need to keep those penetrations free of all other services. It is also essential for the contractor to use the penetration seal system specified by the damper manufacturer.
Damper penetrations in dry lining partitions must be framed and designed to ensure the continuing stability of the partition as a whole. How the damper and ductwork is supported is another area of contention, but testing by the BRE has shown that 'clamped' damper assemblies continue to function and remain in situ during a fire so long as the arrangement is fully supported back to the slab.
It is important to make sure the damper fits perfectly into the ductwork and does not allow fire/smoke leakage around its edges and seals. System designers must also take future damper maintenance into account, which means allowing for practical access around and into the ductwork.
Issues like this must be flagged up and tackled as early in the process as possible because once ductwork and other services are installed, it is very difficult and expensive for the damper arrangement to be modified. DW/145 provides check lists for the design, installation and handover and if a potential problem is identified during the design process then the CDM co-ordinator is in a better position to resolve it.
Test standards have been in place for many years, but there were no nationally recognised criteria covering their integration into the building structure until DW/145 came along. In the past, it was left to various members of the project team to make their own decisions about how dampers should be installed - often those decisions were based on individual preference or opinion rather than certified test results and best practice.
Responsible manufacturers should be wholeheartedly behind the adoption of the recommendations in DW/145 and be geared up to provide project specific information at a stage when it is still possible to make changes. This, and keeping in close contact throughout the process, will help contractors deliver a compliant solution that keeps building occupants safe and building owners on the right side of the law.
// The author is managing director of Ruskin Air Management //