Industrial hygiene is the science and art dedicated to the anticipation, recognition, evaluation, and control of workplace hazards that may cause worker injuries or illnesses. The industrial hygienist, while concerned with physical safety, focuses on the prevention of worker illnesses caused by workplace exposures to various chemicals, substances, and elements. The industrial hygienist must be capable of anticipating workplace hazards. The evaluation process may require the use of specialized sampling equipment to actually quantify the workers' exposure to the specific hazards. There is a wide variety of industrial hygiene sampling equipment available for air sampling. This chapter discusses the type and applications of the most commonly used equipment and media. The types of air sampling that can be performed include: grab sampling, personal sampling, area sampling, integrated sampling, and direct reading. Direct-reading instruments are valuable tools for detecting and measuring worker exposure to gases, vapors, aerosols, and fine particulates suspended in air.