Level of Hazards

LEVEL OF HAZARDS

High Level of Hazards

Whenever work is to be carried out on the MGPS, it is assigned a level of hazard depending on the nature of the work.

It is important to appreciate that the hazard level relates to risks to the patient, not to the system maintainer or operative.

Two levels of hazard are defined

Low Level of Hazards

• High hazard work is work on any part of the MGPS that introduces hazards of pollution and/or cross-connection or isolation of a patient supply other than for servicing terminal unit second-fix components.

• High hazard work will require subsequent tests for gas quality and/or identity and performance of fittings etc (including the ability to deliver the designed gas flow).

• Cutting and brazing a pipeline is classified as high hazard, as it is clear that both cross-connection and pollution are possible consequences of the work.

• There are instances where a cross-connection hazard may arise but the risk of system pollution is very small. Examples would be the servicing of terminal units with interchangeable components (that is, those not designed to BS 5682:1998 specifications) and the moving of pendants containing flexible hoses fitted with mechanical connectors (NISTs).

• Replacement of pendant hoses also carries a risk of cross-connection should NIST fittings be incorrectly attributed to a hose. This is a possibility when hose assemblies are not colour-coded as recommended. In this situation, the performance of a simple anti-confusion test by use of, for example, AVSUs and gas-specific probes may suffice; a gas identity meter check may be waived at the discretion of the Quality Controller (MGPS).

• If the risk of pollution is negligible and that of cross-connection is minimised by operational procedures, testing with a gas identity meter may not be necessary.

• Servicing of terminal units containing interchangeable components is a typical example. As these types of terminal unit may also require isolation of a ward, the risk of cross-connection can be minimised by replacing seals on the one gas system that has been depressurised. Other systems remain pressurised during the work. If formal gas identity meter-testing is not carried out, final proof of correct identity must be proved by mechanical testing using gas-specific proofing tools (for example certified gas-specific terminal unit probes).

• In all such cases, it is essential that procedures are agreed with the Quality Controller (MGPS) and are documented in the MGPS operational policy.

• Isolation of, say, a single compressor, or even a complete compressor system, for an oil change would be classified as low hazard, provided that the emergency reserve supply is active, capable of supplying system demand, and monitored during plant isolation.

• A vacuum system could be crucial to patient welfare. Complete isolation of a vacuum system is therefore classified as high hazard work, and will require provision of portable vacuum pumps and/ or ejector-type vacuum units.

• This applies to all work on the MGPS that does not give rise to a high hazard situation.

• Low hazard permits will cover all PPM inspections, but some remedial work may require issue of a high hazard permit; for example, examination of a leaking terminal unit may reveal that the supply to the ward will require isolation in order to allow replacement of a damaged first-fix component.

• Much low hazard work will involve maintenance of terminal units either on a PPM basis or as an emergency repair (replacement of second-fix components).

• Terminal units that comply with BS 5682:1998/ BS EN 737-1:1998 incorporate components such as indexing pins and shapes which are gas-specific. It is therefore not possible to assemble the terminal unit in such a way that the wrong gas is delivered (other than by a wilful act). Servicing of these terminals is therefore low hazard work. However, during re-assembly the gas-specific features should be checked to ensure that they have not been damaged. The removal of gas-specific features from second-fix assemblies (for example locating pins) must not be used as a method of overcoming incorrectly installed first-fix components.

• Terminal units complying with BS 5682:1998 include an automatic isolating valve. Some earlier terminal units include a manual isolating valve.

• When working on individual terminal units fitted with an integral isolating valve or check valve (which operates automatically when the socket assembly is removed), it is not usually necessary to interrupt the supply to other adjacent terminal units.

• Terminal unit termination blocks should not be left unattended with the socket removed, unless a blocking plate has been attached.

• In some cases, the hazard level may appear high, for example changing bacteria filters on a central vacuum plant. However, this task would be classified as low hazard, as patient risk is low, even though maintenance staff should take special precautions against infection.

• Risks to personnel working on the MGPS may arise from the work procedures or work environment, for example microbiological exposure, brazing (hot work) and work in confined spaces. Working with these risks may require issue of additional permits appropriate to the risks. These permits may run concurrently with the MGPS permit, and they should be referenced on part 1 of the MGPS permit.