Oxygen and fuel gas cylinders used for welding and cutting must meet the requirements of DOT and CGA (Compressed Gas Association) standards. Cylinders must be securely fastened in an upright position and protected from falling or being knocked over. Cylinder valves must never be closed or opened quickly as this can cause dangerous pressure surges. Storage areas must separate oxygen from fuel gas cylinders by at least 20 feet or use a non-combustible barrier at least 5 feet high. Oxygen cylinders must never be stored in the same location as grease, oil, or flammable materials as oxygen accelerates combustion. Acetylene cylinders must be stored in an upright position and must not be used if lying on their side. Manifold systems must have proper pressure gauges, check valves, and flashback arresters to prevent backflow of gases. Regulators must be sized and maintained properly to control pressure according to the work being performed. Hoses must be color-coded: red for fuel gas, green for oxygen, blue for inert gases. Hose connections must be secured with clamps or fittings appropriate to the gas being carried. Welding cables and clamps must maintain proper electrical contact for arc welding. All personnel performing gas welding or cutting must be trained and certified. Hot work permits must be obtained and fire watches must be stationed throughout the operation. Fire extinguishers must be available at all welding operations.