Passive control: the problems involved in the selection of suitable materials for use in enclosed environments and conforming to different international legislation

摘要

The selection of materials suitable for use in submarines is complex. There is a need to achieve technical suitability to maximise operational capability. There is also the necessity to comply with through-life requirements including health and safety, occupational, and environmental legislation. In selecting materials the risk to crew and the vessel must be reduced to as low as is reasonably practicable (ALARP). Submarine crews are enclosed for continuous periods each possibly lasting up to 90 days. For this patrol cycle the Royal Navy (RN) has to comply with UK legislation and additional requirements to adjust for the unusual working and living patterns that are encountered in an isolated environment. When selecting materials different types of hazards have to be considered: inherent, particulate, and fire toxicity hazards, the latter resulting from early onset of fire conditions (e.g. off-gassing because of overheating) through to complete combustion. The passive control process utilised by the RN aims to avoid or limit the use of toxic materials within the confines of the submarine to achieve the following aims: (1) Acute and chronic health risks to crew will be minimised ALARP; (2) Mental and physical crew performance must be unimpaired; (3) Submarine installed equipment must not be degraded to an unacceptable level; (4) Other risks must not be aggravated by the introduction of new contaminants in the submarines atmosphere. In this paper, the authors describe in detail the different types of hazards to be mitigated and the difficulties involved in trying to provide suitable hazard identification to the key stakeholders: builders, maintainers and operators. The information collated by the toxicologist enables key stakeholders to minimise risk to ALARP during normal use, and also considers potential hazards that might be generated when a product suffers damage. The purpose is to give confidence that hazard and risk information relating to the most technically suitable materials is assessed correctly and that materials selected conform to UK, European, and RN policy even when procured from countries external to Europe. It is important to ensure that any toxic substances introduced into the enclosed atmosphere comply with relevant exposure standards. There can be many different nations involved in the supply chain each controlled by various national and international governing bodies defining their own acceptable safety criteria. Consequently, the relevant safety criteria need to be evaluated in context of the RN's requirement for a sealed environment, and assessment must be made as to whether the hazards and risks determined for the enclosed environment are manageable during routine operation and emergency conditions, especially if a compromise in material selection was inevitable due to maintaining operational capability. The requirement for material selection is not exclusive to the enclosed breathable atmosphere of submarines but all sealed atmospheres isolated against harsh environments.