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It also requires the provision of 'safe systems of work' and appropriate rescue plans.
Health and Safety at Work Regulations 1999
Under the Management of Health and Safety at Work Regulations 1999 (SI 3242), employers are required to assess the risks of each process and task undertaken in the enterprise.
In order to minimise risk, practices and training must be aligned to the results of these assessments. If you start with legislation you really need to be complete so HASAWA 1974 should also be referenced.
The use of industrial gases may affect the gaseous composition of the atmosphere within a working environment.
Many processes, such as welding and cutting, not only consume oxygen from the air around but may also create gaseous contaminants.
Ultra violet light from electric arc welding may also affect the oxygen in the atmosphere in close proximity to the weld.
- one of the most dangerous risks associated with gas use is asphyxiation caused by the reduction of oxygen in the atmosphere due to gases leakage
- systems used to carry gases to their point of use should be leak free. All joints must frequently be tested with an approved leak test solution
- it should be noted here that when working with cryogenic liquids such as nitrogen, the expansion of liquid gas into its vapour state may create an additional risk of asphyxiation
- one litre of liquid nitrogen will expand to 683 litres of nitrogen gas. Nitrogen gas does not support life
- attention must be given to vessels used for storing gases in their liquid form as open vessels will constantly leak gas into the environment
- pressurised vessels are fitted with relief valves and burst discs which may allow gas into the working area
There are special guidance notes on the storage of cryogenic gases within buildings.
The British Compressed Gases Association has also published a Code of Practice (number CP30) which gives guidance on the safe use of liquid nitrogen dewars.
There are special guidance notes for entry into confined spaces where it is suspected that the atmosphere is dangerous. Breathing apparatus will be required and the user must know how to operate it. Help should be summoned immediately. It is important to note the time of entry into the suspect area and the condition and contents of breathing apparatus.
- the use of fuel gases such as acetylene, propane and hydrogen may create the risk of explosion
- leaks of fuel gases into the working environment allow the creation of flammable or explosive mixtures in air
- the flammability range of each fuel gas is different: some gases have a very low 'lower limit' which means that in a poorly-ventilated working environment an explosive mix can be rapidly created
- additionally, the energy required to ignite some flammable mixtures is very low, thus increasing the risk further
- fuel gases are also asphyxiants; leaks will reduce the amount of breathable oxygen in the vicinity.
- in order to understand where leaks will accumulate it is important to know for each gas used if it is heavier or lighter than air
- the risk of fire is significantly increased when the atmosphere has greater than normal oxygen content
- this may happen if an oxygen system is leaking into the work area
- materials which do not usually burn in air may do so in an oxygen-enriched atmosphere
- the amount of energy required to ignite a material in an oxygen-enriched atmosphere is also reduced
- great care must be taken if individuals are exposed to an oxygen-enriched atmosphere as clothing and hair absorb oxygen. If you suspect this may have occurred, removed all individuals into the fresh air immediately. They must remain there for at least 15 minutes to normalise the situation. The source of the leak must be traced and sealed off.
Toxic gas leak
- extreme care must be taken to prevent the leakage of toxic gas into the working area
- toxic gases are asphyxiants
- the risk of leakage is minimised by the correct management of the working atmosphere
- adequate ventilation is vitally important
- some production situations may require forced ventilation in order to ensure the working atmosphere remains normal in terms of the breathable oxygen content
- contaminants such as carbon dioxide and carbon monoxide (which are often present as the products of combustion) must be removed to a safe place
- gas monitors indicate the level of gas in an area
- gas monitors are specific to a gas
- gas monitors are also available to assist in the indication of increased risk
- monitors indicate where a problem exists, but they do not solve the issue
- full risk assessments are vital
- it is important to understand that operators may be adversely affected by an abnormal atmosphere and may be unable to judge situations and react at normal speed
- entry into confined spaces must be covered by a 'safe system of work' (e.g. Permit to Work scheme), based on a method statement
- the requirement to personally check and inspect
- clear information
The system should address the following points:
- the requirement for proper authorisation of the designated work to be carried out
- the need to clearly state the hazards, any limitations and the time period permitted for the work
- the precautions to be taken
- the need to identify the person in direct control of the area and the equipment upon which the work is being carried out
- the requirement for continuous control and recording of work, the precautions and the checks made
- the need for the permit to be clearly displayed
- the possibility that the work may be interrupted
- the possibility that other works / other permits may have to be cross-referenced for interactions which could affect safety (e.g. by a control person aware of isolations prevailing, etc.)
- the need to provide a formal issue procedure
- the need to provide a formal completion procedure