RISCAuthority Seminar
a higher concentration of toxic gases. Styrofoam meanwhile emits carbon monoxide, while stonewool does not burn, and only the binding material – depending entirely on the manufacturer – will burn. In terms of acute toxicity, the gases released
by these materials have an ‘immediate effect’ on people, including smoke obscuration which causes impaired vision and irritation. Irritant gases create breathing difficulties but, depending on concentration, can cause lung inflammation and death; while chronic, long term effects can persist if an individual survives. Asphyxiant gases meanwhile create confusion and then loss of consciousness, with carbon monoxide and hydrogen cyanide most culpable here – survivors of Grenfell were treated with cyanide kits. Carbon monoxide provides a slow ‘insidious’ toxification by quickly replacing oxygen and remaining stable in the blood, whereas hydrogen cyanide is far more toxic, rapidly circulating to the lungs, heart and brain and causing unconsciousness. This gas is a ‘major cause of rapid incapacitation’
– Polish house fire deaths examined found a soot presence in 80% of deaths (if the percentage is above 50%, carbon monoxide is to blame). Of these people, 83% died in the room of fire origin close to the furniture or floor containing toxic materials. Professor Stec then examined the fraction of lethal doses (FEDs) in fires, and the toxicity of certain polymers and the gases they create, before looking at insulation materials in the same way. Stonewool and glasswool emit the least number of gases, while PIR emits the most. Referring back to chronic toxicity, she remarked that firefighters suffer most with this due to the increased absorption of soot particulates through their skin and throat. As flame retardents increase fire toxicity,
many of these materials have been banned in Europe and replaced. Professor Stec explained that the bigger threat now is from soot on walls, in ash and in residues, which if inhaled can achieve deep lung penetration. Phosphorus fire retardents are increasingly used due to bromine and chlorine source retardents being banned, but she pointed out that these can potentially emit neurotoxins, and so are restricted in sofa or chair foams, but are used on buildings.
Timber construction
Dr Rory Haddon of the University of Edinburgh spoke on the fire risks in modern timber construction, and cited examples of such construction including the proposed ‘Matchstick’
FOCUS
tower at the Barbican in London. Asking why timber was ‘having a renaissance’, he noted that this was not regarding timber frames but cross laminated timber beams, which are lightweight, can be quickly constructed and appear natural, though they behave in a way in fire that is ‘difficult to predict’. The panels are made by gluing individual
panels together in a sandwich, and this provides efficient structural performance, but also a ‘unique set of risks’. While all materials present some risk element, Dr Haddon highlighted the myths around timber, including that it doesn’t burn, but chars. To this, he retorted that the length of time campfires last are enough to suggest that charring still radiates heat and continues a fire. Another myth is that it burns in a ‘slow,
predictable manner’, though he didn’t disagree with this so much as the claim that if timber can achieve 120 minutes’ fire resistance, a building constructed with it can survive for two hours, calling this a ‘huge misconception’. While sprinklers may help in such an event, you ‘can’t blindly apply one solution to this issue’ and can miss other challenges posed, with 120 minutes’ resistance not two hours of real time in a fire.
On the idea of timber burning slowly but
predictably, he notes that fires increase rapidly at the start and then remain steady when a solid piece of timber is burned. However, cross laminated timber when exposed to the same tests has ‘huge spikes’ of heat and flame. Solid wood in this sense is ‘predictable’, but engineered products are not.
www.frmjournal.com JULY/AUGUST 2018 41
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64
