This chapter discusses the concentrate on a few of the most common gases and vapours that are seen in industry and examine their implications for health and hygiene in the workplace. The occupational work environment may contain vast amounts of atmospheric contaminants, many of which can be categorised into gases and vapours. Although many gases are essential to life, air that is contaminated with hazardous gases and vapours risks workers’ health and wellbeing. Gases range from simple gases such as helium to complex hydrocarbon compounds found in the petrochemical industry. While some gases and vapours may be dissolved in the moisture of the upper airways, others can reach the alveolar regions of the lung, from where they may pass into the bloodstream. Fixed-location instruments typically are found in processing plants where fugitive gases and vapours can pose potential hazards to unprotected workers.