Are other sources of ground gas a risk

Historically there have also been incidents of methane migrating from coal mines and causing explosions in coal mining areas in the UK. 

As far as the authors are aware there have not been any explosions or other incidents in the UK caused by ground gas migration into above-ground buildings from natural soiu-ces such as alluvium, chalk, limestone and peat. There have not been any recorded incidents where either methane or carbon dioxide have migrated from undisturbed coal measures into buildings. 

An explosion occurred in a pumping station at Abbeystead, Lancashire, UK in 1984 (Hooker and Bannon, 1993). This was caused by methane accumulating in a tunnel constructed in coal measures strata. The source of the methane was 

---