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Chemical suits - part 2

Workers in the emergency services can choose different levels of protective clothing to suit the circumstances.

The threat of terrorist attacks utilising chemical, biological or radiological agents remains at a high level. Protective suits have been available to the military for many years, but in recognition of the heightened terrorist threat, and indeed of the danger posed by an accidental release of toxic substances, there is a need to provide emergency services with suitable protective equipment in the event of an incident. Until recently, there were no specific standards covering this type of garment and therefore a new British Standard has been developed and published.

BS 8467:2006 Protective clothing – Personal protective ensembles for use against chemical, biological, radiological and nuclear (CBRN) agents covers categorisation, performance requirements and test methods relating to PPE products. There are no specific European standards covering CBRN for non-military use, and BS 8467 has been developed using existing test methods and protocol to facilitate ease of testing and the CE marking process. Whilst military protective clothing is exempt, occupational garments for non-military applications need to comply with the Personal Protective Equipment (PPE) Regulation.

BS 8467 contains performance requirements and test methods for protective ensembles including garments, gloves, footwear and eye, face and respiratory protection. Four levels of performance are recognised and these are known as categories A to D where A provides the highest level of protection and D the lowest.

The principle behind the categorisation in this standard is to provide emergency services personnel with a range of protection to suit the circumstances. For instance, people operating very close to the centre of an incident where the concentration of an agent is known to be high (or indeed where it is not known) require a very high level of protection. At the opposite extreme, emergency services operating a long way from the incident or where the risk level has already been established as low, require a lower level of protection, perhaps for wearing over a period of several hours.

Levels of protection

Category A covers the equipment required at the centre of an incident, and consists of gas-tight suits with independent air supply, protecting against CBRN agents in the form of vapours or gases. It is recognised that this type of protection might come at the expense of mobility and duration within the contaminated zone. Such ensembles should conform to EN 943-2, the standard for emergency team gas-tight suits.

Category B equipment can be worn for longer periods in situations where contact with contaminated surfaces and residual vapours may occur. Liquid-tight ensembles satisfying type 3a or type 3b emergency team PPE requirements as detailed in BS 8428 would provide the necessary protection.

Category C equipment is for use where the exposure is to low levels of known agents and where risk of skin contact is minimal. It is envisaged that such suits would be used in activities such as the rescue of casualties from a collapsed building so a high level of mechanical strength is required from the garment. Garments meeting EN 469:2005 – Protective clothing for firefighters, would meet this scenario’s requirements for physical strength, dimensional stability, surface wetting, resistance to chemical penetration, resistance to water penetration and resistance to ignition. However the thermal properties required in EN 469:2005 are not relevant.

Category D equipment would be used where only very low levels of contaminants exist, either because users are operating a long way from the centre of the incident or because users are operating a long time after the incident. The basic chemical suit could consist of a type 6 suit conforming to EN 13034:2005.

Image © Trelleborg Protective Products

Emergency workers at the heart of an incident require gas-tight suits with independent air supply

Threat from the atmosphere

Preventing inward leakage of airborne particulates is a key requirement. All categories of protection under this standard are required to meet an inward leakage performance level of 0.01 per cent or better for category A, 0.05 per cent or better for category B and 0.1 per cent or better for categories C and D. A range of test methods is described including using human subjects wearing the ensembles whilst walking on a rolling road in a test atmosphere. Other methods involve the use of a dynamic manikin in live agent tests. Test atmospheres for manikin type tests could be, for instance, distilled sulphur mustard HD, Sarin GB, Soman GD or V-agent. For human subject tests, an atmosphere with sodium chloride aerosols is used.

All materials used in the ensembles must also be assessed for their resistance to the permeation of distilled sulphur mustard HD, Sarin GB, Soman GD or V-agent. These tests are in addition to any permeation testing or penetration testing which the various items in the ensemble may have already undergone. For example, EN 943-2 includes a test bank of 15 chemicals – including both liquids and gases – which all components of the ensemble must protect against. The permeation test specified in BS 8467, however, requires a specific quantity of chemical to be applied to the test piece. For category A this concentration is 100g/m2, whilst for B, C and D it is 10g/m2. The maximum cumulative permeation over four hours should be no more than 1.25 µg/cm2.

Other components

Whilst this article concentrates on clothing, it is vital that suitable protection of the hands, feet, head/face/eyes and respiratory system is also provided. Normative references in BS 8467 detail harmonised European standards to be used covering these products.

All of the ensembles in BS 8467 are composed of several items of personal protective equipment and therefore they fall within the scope of the PPE Regulation unless manufactured specifically for the armed services or police.

Further information on SATRA's PPE certification and testing services is available at www.satra.com/ppe

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SATRA is able to test and certify protective clothing and equipment against the PPE Regulation. SATRA is also able to carry out the ongoing audit of production of such items. Please email ppe@satra.com for more information.