Current affairs As a fire grows, toxicity remains high unless there

is ventilation. Its significance grows if there is no ventilation, through carbon dioxide (CO2

), CO and

HCN. Toxicity is usually only tested in well ventilated conditions, but Dr Hull argued that it should only be tested in controlled, underventilated scenarios. He also covered the fraction of lethal dose (FED)

equation, which allows for an estimation of fire toxicity – 1 FED would kill 50% of the exposed population. Humans breathe quicker when there is more CO2

, and

might inhale HCN and other toxic chemicals, burnt polymers releasing substances such as hydrogen chloride (HCI) or nitrogen. Toxicity depends on material composition and conditions, with cabling materials releasing more HCI and CO, while polyisocurante (PIR) or polyurethane (PUR) foam can release HCI and CO, and levels increase in any underventilated scenario. Dr Hull asked Dame Judith about testing for toxicity,

and she replied that all materials should be examined on a risk case basis. He then covered the toxicity of polyamides that work as flame retardants, which often results in a huge increase in HCI and CO due to the presence of bromide. Insulation materials’ heat release sees foams peak

immediately but burn ‘pretty well’. Many victims died on Grenfell’s stairwells, and it was established that they had died of HCN poisoning. Exposure causes respiration to increase by a rate of four, and deprives the body of oxygen, resulting in unconsciousness immediately – it is also ‘rapid’ even at a low dosage. With CO, unconsciousness only comes quickly if there is a huge amount in the air – most Grenfell victims fell unconscious due to HCN and died due to the CO. The study looked at different insulation materials

with ACM, and found that PIR makes a ‘huge contribution’ to incapacitation compared to phenolic foams. The first test combined stonewool and ACM rated at A2, a combination ‘never found in UK high rises’. Here, ACM ‘disappears’ and offers no protection, while PIR and ACM was ‘not much different’, but saw more flames. However, phenolic foam and ACM saw ‘big piles’ fall off, and the test was stopped after 12 minutes as it posed a structural threat to the laboratory. All tests presented very little difference in heat

release, exhaust duct data showing that PIR particularly made a ‘relatively small’ contribution. CO2


CO and HCN were all present, and lethality would come from depletion of oxygen and increase in CO2


Dr Hull noted that we ‘don’t usually expect death from oxygen depletion’. A kitchen vent was constructed horizontally and then vertically from the rig, and during the PIR test, fire broke through the vent, causing oxygen to deplete and CO2

and CO to increase, so ‘all hell

broke loose’. HCN and CO levels were ‘right up’, and underventilation brought them inside, implications including a ‘significant contribution’ from PIR of HCN and CO.

Dr Hull noted that toxicity is the ‘biggest cause of death or injury, but is not regulated’, and material

composition has a ‘huge effect’ on toxicity. Yields of HCN and CO increase when toxicity grows, and the emphasis on insulation has left building regulations ‘way behind’ modern builds.

Legislative change?

Discussing how the Hackitt Review might affect development of new legislation, FPA principal consultant Howard Passey explored ‘where we are at the moment’, warning that ‘these are only recommendations’, and could change through implementation, while the idea of ‘layers of protection’ for buildings will be significant. At each step, all involved will need to understand how these ‘layers’ work, and apply regulations ‘effectively and correctly’. It will be important to ‘effectively design in safety’

and ensure an ‘effective change process’, Mr Passey then exploring potential changes to Approved Document B of the Building Regulations (ADB). Simplification had been ‘requested’ alongside easier implementation, with the Construction (Design and Management) Regulations 2015 an ideal benchmark because they provide oversight and a ‘template for the way forward’, with creation, maintenance and handover of relevant information ‘integral to legal responsibilities’. Doing this would mean applying details to ‘all types’ of multiple occupancy building. Broadly welcoming the combustible materials

ban, but adding that ‘we need to consider if the ban goes far enough’, Mr Passey then returned to the Hackitt recommendations, noting that they had drawn up responsibilities for each part of the construction process. He believed however that there FEBRUARY 2019 41


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