Gas Blending - Hazards

Hazards

There are several hazards with gas mixing:

• cylinders are being filled with high pressure gas. If there is any damage or corrosion in the pressure vessel or valves of the cylinder, this is the occasion when they are most likely to fail structurally.
• oxygen supports combustion; if it comes into contact with fuel and heat the three ingredients for a fire exist. Fires in the presence of high concentrations of oxygen burn more vigorously than those in air. A fire in the presence of high-pressure gas may cause cylinders to fail.
• other high pressure equipment such as whips, compressors, gas banks and valves are being used, which can cause injury if the pressure is released
• there are dangers of fire from the fuel and electric power supplies of the compressor
• there are dangers of injury from the moving parts of the compressor
• there is the possibility of asphyxiation due to the presence, in a confined space, of large volumes of gases that contain no oxygen, such as helium

It is possible for gas blenders to create toxic and dangerous gas mixes for divers. Too much or too little oxygen in the mix can be fatal for the diver. Oxygen analysers are used to measure the oxygen content of the mix. In good blending sites, the contents are analysed in the presence of the diver who acknowledges the contents by signing a log.

It is possible that poisonous additives, such as carbon monoxide or hydrocarbon lubricants, will enter the cylinders from the diving air compressor. This is generally a problem with the compressor maintenance or location of the air input to the compressor though it can be from other sources.

Poisonous additives can also get into the breathing mix if any material inside the blending valves or pipes burns, for instance when adiabatic heating occurs when decanting or boosting oxygen.