Compressed gases and liquids stored in cylinders at 29 psi or higher presents various hazards. Cylinders are heavy and potential release of pressurized gas can inflict physical harm. Once gas is released, it expands and displaces oxygen, resulting in asphyxiating conditions especially if released in a small space with inadequate ventilation. The gases themselves may be inherently toxic such as carbon monoxide, ammonia, arsine and many others or they may be flammable such as hydrogen, methane, propane and my others. The safe handling of compressed gases [docx] contains important hazard and controls information that researchers need to know when working with compressed gases.