This text provides a reference source for finding out what methods and techniques are available for the detection of methane and other gases from the ground. The book also describes how to sample these gases and take measurements relevant to mitigating the problems they pose. While centred on methane and landfill gas, the book covers carbon dioxide and other hazardous gases too. There is comprehensive guidance on detecting gas, identifying the source, measuring and sampling different gases, and on the interpretation of the results. Also features the use of monitoring systems on site and within buildings.