09Jul / 2015
BS 8485:2015 – Code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings
BSI have just published the long awaited revision to the 2007 document.
Toxic, asphyxiating or explosive gases can leak from the ground and accumulate in buildings, posing health risks. The standard describes how to characterize sites and prevent the entry of carbon dioxide and methane into new buildings. This revision has now been substantially expanded and revised to reflect changes in good practice and reference other standards since the last edition was published.
The revised document provides the highest level of guidance in the UK on this subject and while keeping to the ethos and spirit of the simple point scoring system of design, it is much expanded to provide clearer guidance on:
- interpreting gas monitoring data
- selecting membranes
- changes to gas protection scores
- worked examples
- user flow charts
And in addition to methane and carbon dioxide it also provides recommendations through new annexes on radon and volatile organic compounds (VOCs).
Hazardous gases may be present in the ground naturally, or from contamination, mine working or buried wastes. Two of the major risks are methane, which is flammable (explosive in confined spaces) and an asphyxiant, and carbon dioxide, which is both toxic and an asphyxiant.
The standard provides guidance on site investigation, determining ground gas parameters and using those to identify protective design solutions. It is not prescriptive – recognising that there are many factors involved, that a range of design solutions are available for different situations, and that professional judgement is often needed. Emphasis is placed on justification and recording of risk assessments and design decisions so that the whole process will be transparent for consultants, developers and regulators.
Ground-Gas Solutions Comment
Ground Gas Solutions works hard to promote best practice in the contaminated land sector and believes that this document provides a further step forward to improved ground-gas protection for the UK construction industry. The document can be obtained from http://shop.bsigroup.com/ProductDetail/?pid=000000000030283600