Safety and standards

Because the contents are under pressure and are sometimes hazardous materials, handling bottled gases are regulated. 
Regulations may include chaining bottles to prevent falling and damaging the valve, proper ventilation to prevent injury or death in case of leaks and signage to indicate the potential hazards If a compressed gas cylinder tips over, causing the valve block to be sheared off, the rapid release of high-pressure gas may cause the cylinder to be violently accelerated, potentially causing property damage, injury, or death. 
To prevent this, cylinders are normally secured to a fixed object or transport cart with a strap or chain.
In a fire, the pressure in a gas cylinder rises in direct proportion to its temperature.If the internal pressure exceeds the mechanical limitations of the cylinder and there are no means to safely vent the pressurized gas to the atmosphere, the vessel will fail mechanically. 
If the vessel contents are flammable, this event may result in a fireball.
Oxidisers such as oxygen and fluorine will produce a similar effect by accelerating combustion in the area affected. 
If the cylinder's contents are liquid, but become a gas at ambient conditions, this is commonly referred to as a boiling liquid expanding vapour explosion (BLEVE).
Medical gas cylinders in the UK and some other countries have a fusible plug of Wood's metal in the valve block between the valve seat and the cylinder.
This plug melts at a comparatively low temperature (70 °C) and allows the contents of the cylinder to escape to the surroundings before the cylinder is significantly weakened by the heat, lessening the risk of explosion.
More common pressure relief devices are a simple burst disc installed in the base of the valve between the cylinder and the valve seat. 
A burst disc is a small metal gasket engineered to rupture at a pre-determined pressure. Some burst discs are backed with a low-melting-point metal, so that the valve must be exposed to excessive heat before the burst disc can rupture.
The Compressed Gas Association publishes a number of booklets and pamphlets on safe handling and use of bottled gases.