BS 8478 – Breathing Gases for Diving and Hyperbaric Applications
This standards is virtually impossible to achieve using air produced by standard breathing air compressors and the low levels of contaminants required cannot be effectively measured by conventional methods; it makes a laboratory test the only reliable method.
The HSE is well aware of the practical problems that this standards poses for recreational diving operations. A European version of this Standard is being developed. No doubt, when the EN standard is published, further HSE guidance will follow. In the meantime, ASSET Members are advised to ensure that they are producing air, particularly for the production of Nitrox or Tri-mix, to the highest practicable standard.
Meeting the low oil level required will be the greatest challenge. Adding a high volume, low velocity secondary filter (as recommended in the ASSET Nitrox Manual) that provides maximum "Dwell" of the air being filtered will go some way to achieving this.We also recommend that filters are replaced in good time and that any air purity test is carried out at the end of the filter's life not when it is new. This will ensure a "worst case" measurement.
Additionally, we recommend that, in addition to any quarterly "in house" testing that may be carried out, a laboratory test is carried out at least 6 monthly intervals. A relatively economical and practicable laboratory test is available from Aquatron in Glasgow. http://www.airpurity.com/how_apa.htm
Please also read the following HSE guidance:
BS 8478 – Breathing Gases for Diving and Hyperbaric Applications
British Standard 8478 specifies requirements for the composition and purity of breathing gases, other than compressed air, for diving and hyperbaric applications. It specifies reduced levels of contaminants compared with those required to meet the compressed air standard, BS EN 12021. HSE supports British Standards as a means to enhance safety and provide guidance to industry. In particular HSE endorses the need for increased gas purity, over and above the levels required in BS EN 12021, where equipment is exposed to oxygen levels greater than 21% and for gas mixes used at increased depths. Compliance with a British Standard is, however not a legal requirement but their observance provides a means of demonstrating that appropriate risk controls have been applied. It is open to gas manufacturers/providers to produce gas to their own standard provided these also apply appropriate risk controls. Ultimately it will be up to the courts to decide if such other standards are sufficient.
HSE is aware that areas of the recreational diving industry have concerns with some aspects of BS 8478. It is believed these concerns are based on whether the demanding purity criteria are justified for all gas mixes used in recreational diving, as well as the potential impact the standard could have on the continued use of Nitrox in the recreational sector.
BS 8478 is currently being considered as a basis for a new European standard. When this European standard is finalised it will supersede BS 8478 which will then be withdrawn. The process for developing the new standard is now underway within Europe and the resulting standard will almost certainly be different in some respects from the current BS 8478.
In the interim period before the European standard is finalised and published HSE expects the recreational diving industry to take all reasonably practicable steps to minimise the contaminants in the gases other than air which they provide, and where practicable to meet the contaminant criteria detailed in BS 8478. These steps should include robust systems of work to ensure that any impurities are maintained at the lowest levels practicable as well as periodic tests to ensure the contaminants are maintained at these low levels. BS 8478 currently requires testing at least every 6 months.
In the event of diving incidents where gases other than air have been used, the breathing gas composition and purity criteria in BS 8478 will continue to be referred to as part of the investigation process. Should these investigations lead to legal proceedings, and the gas provider did not follow the requirements in BS 8478, it will be up to a court to decide if the steps taken to ensure the purity of the breathing gas were sufficient.
Recreational diving gas providers may wish to take account of the views of their insurers when deciding their course of action.
The process for developing the new European standard is now underway. Stakeholders within recreational diving are urged to actively participate in this process to ensure the new European standard both enhances safety and is workable for all sectors of the diving industry.
E062:0616 May 2006
HSE issues precationary advice after dive cylinder valve fails
The Health and Safety Executive (HSE) has issued precautionary advice to dive shop owners and any other people carrying out gas analysis on diving cylinders after an incident at a dive shop where two people were injured after a valve was ejected from a cylinder.
The incident happened during gas analysis of a Draeger rebreather four-litre steel cylinder, which had been charged with Nitrox. A charging adaptor had been supplied by the customer and was still fitted to the cylinder valve. The cylinder did not have a ‘boot’ that would have allowed it to stand upright unsupported. Instead, the person carrying out the gas analysis held the cylinder upright with one hand.
As the cylinder valve was opened to allow a low flow of gas for analysis there was an unexplained increase in flow causing the cylinder to rotate violently, injuring the hand of the person holding it. As a result, he let go and the cylinder spun off into the shop. A member of the public was injured trying to stop the spinning cylinder with his foot, as he tried to stop it hitting his son. At this point the valve, still fitted with the charging adaptor, was ejected from the cylinder. The cylinder flew out of the dive shop and travelled a further 20 metres before coming to rest outside. The valve travelled about three metres within the shop.
Despite being analysed by scientific and engineering specialists, it is still not clear why there was an increase in gas flow or what caused the cylinder valve to be ejected.
Diving cylinder advice
However, HSE is issuing precautionary advice to reduce the risk of a similar incident happening. In particular, when a charging adaptor is fitted to the cylinder, there is a possibility that if struck it will affect the torque applied between the cylinder and cylinder valve. To reduce the probability of this happening charging adaptors should only be fitted immediately before charging and removed immediately afterwards.
Charging adaptors which are used with pure oxygen or oxygen enriched (oxygen greater than 21 per cent) gases should be suitable for use with oxygen. In order to maintain their ‘fit for oxygen’ status when not in use they should be stored to maintain that status – for example, placed in a clean transparent bag, which can be sealed closed and then placed in a second similar bag.
Furthermore, when carrying out any checks that require the cylinder valve to be opened the cylinder should be secured in a manner that:
allows both hands of the checker to be free.i.e. one hand to operate the valve and the other to hold any test equipment; and does not allow the cylinder to fall over or be dropped.
Note to Editor
The relevant Local Authority normally enforces safety at dive shops. However, due to the nature of the incident, it was agreed that HSE would lead the investigation.
Nitrox is a generic term for oxygen/nitrogen gas mixes with an oxygen content greater than 21 per cent. The cylinder in question contained 40% oxygen.
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Oliver Glackin020 7717 6016
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HSE information and news releases can be accessed on the Internet www.hse.gov.uk/
HSE
Diving Cylinder Labels
(Revision 1)
Please note: if you would like a copy of this information and pictures of sample labels please email me at: fmmeinert@aol.com
or contact the HSE.
For ASSET Qualified Technicians we are able to email you printer ready templates for you to add your own details. Please email me with your Name and ASSET Membership Number/s and I will email you the full guidance information and the label templates.
