If you are planning, undertaking or interpreting gas investigations, this title should help you take sensible gas measurements and then make sense of those measurements. Understanding how hazards like methane, landfill gas and carbon dioxide could present themselves means postulating a conceptual model of the gas regime. But valid interpretation depends upon valid measurements. This book explains how to develop and, with further measurement and interpretation, to refine a model of the relation between the site and gases in the ground. It shows how the systems of measurement affect the values measured, how external conditions alter the gas regimes, and how, by recognising what has and has not been measured, the results of the measurements can be interpreted in the site context.