At IGD we are often asked by prospective clients if they really need a gas detection system and if so how does it fit into their risk mitigation scheme. Whatever the facility and activities being undertaken, risk assessments will be undertaken to analyse risks and evaluate how to eliminate and minimise them. Methods and approaches to do this are well documented with many standards, guides, codes of practice and courses available.
Yet still risk assessment and mitigation can be a minefield particularly when your main role is the management of a facility and your background is a completely different discipline. This article does not set out to repeat what has already been written by others. For an approach to risk assessment the best starting point is the HSE website which provides sound guidance and best practice. Our aim with this article is to consider the role that gas detection plays as part of an overall safety scheme.
Functional Safety Overview
When considering your facility and assessing risks you will consider if processes have to be undertaken and if materials have to be used. If so then control of the process and materials in a safe manner will be of paramount importance. As far as gases and vapours are concerned there are three basics to consider.
Flammable Gas Hazards
For flammable gases DSEAR regulations state that ‘no atmosphere should be above 25% of the Lower Explosive Limit where flammable gases or vapours are in use or could exist’. So if the facility uses or could generate flammable gases or vapours how you prove that will need to be considered.
Toxic Gas Hazards
Toxic gases will usually come under COSHH regulations and as such will be listed on the HSE’s document reference EH40. If the material has an EH40 listing then occupational exposure limits will be detailed. Another information source would be the Material Safety Data Sheets provided by the supplier, again these will list any exposure limits. Where exposure limits are listed you will need to consider how to show compliance.
Asphyxiant Gas Hazards
Asphyxiants are dealt with a little differently. Here the material is perhaps not flammable or directly toxic but will work to reduce Oxygen levels. Here the British Compressed Gases Association produce guidance note GN11 which states ‘that no-one should be exposed to an atmosphere with an Oxygen level lower than 19.5%’. Again you will need to consider how to demonstrate compliance.