HE AVERAGE person in the street could be forgiven for assuming the term ‘non combustible’ means that the material does not burn under any circumstances, and will immediately reference common masonry materials such as brick and stone. We know, however, that the technical definition is a derivative output of a range of tests which can be satisfied by the individual materials presented, or by their construction into systems with other materials that might protect any combustible elements from participating in fire. The problem with the latter approach is that there must be strict adherence to realism with the end use application, and the list of what needs doing to satisfy this can be extensive, complex and controversial. While scale and fire size are easily understood
RISCAuthority insight T
Dr Jim Glockling asks what is more important, material ‘combustibility’ or ‘participation’, when it comes to construction
• lead to an overall increase in the heat output of a fire
• • • •
raise the temperature of the fire
increase the amount of smoke from the fire increase the toxicity of the fire
contribute to fire spread through flaming droplets or surface spread
Our reason for taking this approach is that these may not necessarily be defined by the established tests, leading to poor understanding of the different performances under fire that can be expected from materials which may respond in a number of ways: 1. Ignite easily and sustain flaming thereafter – this is easily understood.
(but even then not necessarily dealt with well), dealing with real world relevant issues such as installation accuracy (or inaccuracy), wear and tear, abuse, repair and alteration over time is very complex – yet no less important. It does seem strange to me that we are quick to accept the need for fire testing (an inference that the world is imperfect and lots of things have gone wrong to result in a fire), yet assume that the built environment is immune to imperfection (testing on perfect specimens). The key thing is that the ‘person-in-the-street’
view of non combustibility (bricks and mortar) provides protection against fire in its most passive resilient form, and the building essentially remains as safe as it started from birth through to its end of life (all other things being equal). The same might not be true of building systems and products that demand the assured maintenance of combustible material encapsulation for ongoing safety, or the life assurance of fire retarding chemical compounds. We believe a more appropriate approach could be a testing regime that determines a material’s potential ‘contribution’ to a fire. When a fire occurs, and lives are potentially put at risk, what is important then are some simple basic performance criteria, and we should be defining whether their presence could:
10 JULY/AUGUST 2018
www.frmjournal.com
2. Ignite only after a sometimes sizeable ignition source is applied, but sustain burning thereafter (less obvious, and perhaps a feature of flame retarded materials).
3. Do not sustain burning, but contribute to increasing the heat release rate of a fire, impacting on it from another source (not obvious without specific equipment and perhaps a feature of materials that char).
4. Do not ignite, or contribute to increasing the heat release rate of an impacting fire – this is easily understood.
Knowledge of these different participation types is essential to forming a good understanding of where materials may be safety deployed. The challenges presented by meaningful built up system testing (the vehicle for the use of materials that can participate by one of three mechanisms described earlier) are anticipated to be so difficult to overcome to the satisfaction of all stakeholders that the simplest and most robust solution is viewed as being the specification of materials that cannot (in their component material parts) participate in fire, at a level that may lessen the safety of people by increasing a fire’s heat release rate, spread, temperature, smoke production, and toxic by-product generation
Dr Jim Glockling is technical director of the FPA and director of RISCAuthority
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