COVER STORY
AN APP-ROPRIATE MEASURE
What is the link between the Ministry of Defence and a smartphone app for calculating safe-wear times for chemical suits? The answer, Lakeland Industries explain, is Permasure.
When the MOD wanted to develop improved fabrics for protection against battlefield chemical warfare agents, they turned to a small UK company with an expertise in the polymers which provide barriers against chemicals. One result was a range of fabrics which not only offer chemical warfare agent protection but also effective protection against a wide range of chemicals. These fabrics form the backbone of the ChemMax range of chemical suits. The second result was the smart-phone app Permasure.
WHAT IS PERMASURE? Permasure is an easy-to-use app which, in simple
terms, calculates safe-wear times for chemical suits based on real-world conditions and the dermal toxicity of the specific chemical. It provides users with a much clearer understanding of how long a chemical suit can be safely worn to ensure harmful volumes of a chemical will not contaminate the wearer.
“But I already get safe-wear time from a permeation test result”
As a user of chemical suits, you might think that, but you’d be wrong. The assumption that a permeation test ‘breakthrough’ of, say, <480 minutes means that the suit can be safely worn for 480 minutes – or even that the suit can be safely worn at all – indicates a very common misunderstanding of what a permeation test tells you.
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Test ‘breakthrough’ is a measurement of when permeation of the chemical through the fabric reaches a particular speed – not when it first breaks through. Permeation tests also fail to account for variations in temperature, yet it is well-known that permeation rate increases with temperature; in summer permeation might be much quicker than indicated by a test. Finally, permeation tests completely ignore chemical toxicity – the fact that some chemicals have very high toxicity (a small amount can cause harm) whilst for others toxicity is low (a larger amount is required to cause harm).
The permeation test and its ‘breakthrough’ is not, and was never intended, to indicate safe-use and it may come as a shock to realise that a chemical may permeate through a fabric long before a test ‘breakthrough’ time. The consequence is many users of chemical suits are not as well protected as they think, or worse, believe they are protected when they are not.
Even the biggest chemical suit manufacturers can realistically provide only a limited range of test results – a few hundred chemicals at most. With 8,000 or more chemicals in use it is almost inevitable that the chemical involved in the incident attended by emergency response personnel is not on the list. So how can you be sure your chemical suit will protect you? Based only on test data, you can’t.
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