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One of the hardest fire protection elements in a building to assess is the fire stopping capability of penetration seals. Bob Settle outlines the types of system available, and what risk assessors should be looking for in buildings.
Compartmentation and the provision of protected corridors and stairways are fundamental concepts in the fire safety provisions embodied in regulations. These objectives are achieved by the incorporation of fire resisting barriers – walls and floors, within a building to provide areas of relative safety.
Unfortunately, modern buildings are full of services, cables, pipes, ductwork and so on, which often need to pass through these fire resisting elements and so have the potential to compromise the protection that they are designed to provide. This can be mitigated by the method used to seal around these services. But even when ‘tested’ materials are used, if the product has not been tested in a construction of the type being used, with a service similar to that which exists and in the same orientation, fire protection can be seriously compromised. Equally, the potential for some of the proprietary systems to produce dangerous levels of smoke production is often unknown.
Risk assessments
Since 1999, buildings that are used for employing people have had to be subject to a fire risk assessment audit under duties imposed by the Fire Precautions (Workplace) Regulations (Amended 1999). This included buildings that were already the subject of a fire certificate issued under the Fire Precautions Act 1971.
In October 2006, England & Wales saw the introduction of the Regulatory Reform Order (RRO) and a year later, Scotland implemented the Fire (Scotland) Act 2005. The RRO repealed the Fire Precautions Act and replaced it with the need for the ‘responsible person’ to carry out, or have carried out, an ongoing fire risk assessment of the premises for which he/she is responsible. It automatically embodies the requirements of the ‘workplace’ regulations’ – as employees are also persons ‘in and around’ the building – and also extends the duty to non-employees. So fire safety moves away from a prescriptive base to a totally risk based system. The fire and rescue service’s role in this process is no longer that of the inspecting authority, but essentially that of the auditor of the risk assessment process. The responsible person, normally the premises owner, takes legal responsibility for the safety of all building occupants.
The objective of these risk assessments is to demonstrate that, in the event of fire, the health and safety of people in and around the building is not at risk. This process extends much further than the audits that were performed to ensure that fire certificate conditions were being satisfied, as were previously undertaken by the fire service under the Fire Precautions Act.
Principles
The services that exist in a modern building are not only plentiful, they can be extremely diverse. Some of the services will have the tendency to burn or melt – large cables or plastic pipes, for example – while others will have the ability to conduct heat from the fire zone to the protected areas. Fire, therefore, has the capacity to exploit the apertures through which these services pass, particularly if the aperture size increases as a result of material burning away or melting. Guidance published in support of regulations generally treats all such penetrations as ‘fire stopping’. There is no bespoke test referred to in this guidance, so it is up to manufacturers to carry out tests, often of their own design, to demonstrate that their products can maintain fire resistance. So the purchaser has the responsibility to ensure whether the test undertaken was realistic and/or applicable, especially in the context of the penetrating service that is being sealed.
Most service penetration seals are tested by analogy to the fire resistance test procedure BS 476: Part 20: 1987. The degree by which the test stresses the sealing system is normally governed by the attitude of the product manufacturer, who can opt for a demanding test or an ‘easy ride’. The lack of a bespoke test means regulatory guidance is very generic in its approach. It permits fire stopping with a variety of cementicious materials, or mineral ‘wool’ products, which may be used as an alternative to proprietary seals. As a consequence, many of the seals that will appear in a fire safety audit may never have been tested at all, and are applied solely on the basis of being listed as suitable in the guidance. The new EN 1366-3 test will improve this when its revision is completed, but a fire risk assessment in existing buildings is unlikely to find an EN tested seal.
With these generic materials there is no guidance as to installation, nor any recognition that they can be rendered ineffective by movement in the service during exposure to high temperature. It is inevitable that services will sag, bow and twist when heated at high temperatures, all of which will have a profound influence on the ability of the seal to provide safe conditions on the protected face. It must also be recognised that a proper barrier should prevent the passage of cold smoke, hot smoke and products of combustion as well as fire and flame – if life safety is to be assured. Yet the materials listed may only satisfy the smoke tightness aspect if installed perfectly and designed to accommodate the anticipated movement in the actual service being sealed when it is hot. Rammed-in, loose fill mineral rock fibre may not have the capability of containing any of the listed hazards, yet this will probably be one of the most common systems found in any penetration sealing audit, especially in older buildings.
Any fire risk assessment auditor must be convinced that the penetration sealing system is matched to the services penetrating the element, and indeed, is able to provide the fire separation within a wall or floor of that type and be retained in position during periods of high thermal movement. Intumescent based penetration sealing systems, on the other hand, are designed to: respond to changes of shape or size of the aperture as a result of movement; resist the penetration by cold smoke in their non-activated state; and provide a ‘hot smoke’ seal when activated.
Different strokes
When auditing plastic pipes, it is important to recognise that the guidance in support of regulations permits 40mm diameter plastic pipe to pass though a fire separating wall – without the need for a heat activated sealing system solely to be fire stopped to the structure. The risk assessing auditor must again feel confident that the development of a hole of that size, which may happen quickly as the plastic melts, will not jeopardise the life safety conditions on the protected side of such a barrier. Similarly, while it is easy to recognise that a pipe closing device exists, it is not sufficient to assume that the type fitted is able to seal the pipe in question. There are a variety of materials from which plastic pipes are manufactured, some of which are more difficult to seal than others. Equally, the selected device must be able to demonstrate its ability to close off pipes not only of the material, but also of the diameter and wall thickness in use. Evidence of its ability to work should always be sought.
It is also vital that pipe closers are physically fixed back to the construction into solid material using fixings that do not melt. They cannot be retained by skim coats of plaster, or by mastics and adhesives – only by fixings that are not compromised by heating and that extend into the non-fire damaged material.
Further guidance on the selection of penetration sealing systems is to be found in the IFSA Code of Practice Sealing Apertures and Service Penetrations to Maintain Fire Resistance, obtainable from the secretariat. But this may not completely answer all of the questions regarding suitability, so you should also liaise with potential providers of the seals systems for any proposed remedial solution.
To conclude, cementicious rigid materials are less likely to maintain fire resistance when the services expand, distort or bow, or the element distorts significantly. Unsealed fibrous materials are unlikely to provide the smoke tightness embodied in the regulatory requirements and enshrined in the life safety codes. A system that can be shown to satisfy an audit will be supported by test evidence which relates to both the active service, the substrate being penetrated (i.e. the wall or floor), and the orientation of the seal relative to the element – vertical element/horizontal service, for example.
If the audited installed seal cannot be supported by test evidence for the particular application, it should be replaced by a system that can be.
Bob Settle is chairman of the Intumescent Fire Seals Association. For the full IFSA guide to penetration seals go to www.ifsa.org.uk/news.php