Sewer systems fall into the category "out of sight, out of mind" - they seldom excite interest. But when things go wrong with the air in the sewer system, they go very wrong. Consequences can be dramatic and devastating: sewer workers killed instantly by poisonous gas when they lift a sewer lid, or entire suburban blocks levelled by explosions. This book describes the atmospheric dangers commonly found in the sewer system. It provides easily-understood explanations of the science behind the hazards, combined with real-life examples of when things went dramatically wrong.