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Fire Safety for Healthcare Premises – Electromagnetic Interference – Part 139

August 3, 2020 1:15 pm

In LWF’s blog series for healthcare professionals, our aim is to give information on best practice of fire safety in hospitals and other healthcare premises. In part 138, LWF discussed visual alarms and looked at radio-linked systems. In part 139, we consider the impact of electromagnetic interference on fire alarm systems.

BS 5839-1:2017 – Fire detection and fire alarm systems for buildings. Code of practice for design, installation, commissioning and maintenance of systems in non-domestic premises talks about how fire alarm systems can be affected by sources of electromagnetic interference. This can be from sources such as radio and cellular telephone transmissions, voltage transients etc.

The interference can cause unwanted fire signals, system faults and malfunctions. In a healthcare environment, the potential for such sources is almost innumerable as it encompasses phones held by members of the public and equipment used to treat patients, such as diathermy equipment.

While it is not possible to eradicate all possible sources of electromagnetic interference, it is possible to investigate those fire alarm systems which are less prone to interference issues and to consider installation parameters. Factors such as the type of cable used, the method of termination and the material from which items such as junction boxes are manufactured may all impact on the immunity of the fire alarm system installation.

In situations where adequate care in choice of fire alarm system and installation procedures has not been taken, mutual interference has been known between fire alarm circuits – e.g. confusion between loops in an addressable system.

The Electromagnetic Compatibility Regulations 2005 and BS 5839-1 provide the requirements which must be complied with in healthcare buildings.

It is imperative that installation design and installation practices should aim to minimise the susceptibility of the installation to electromagnetic interference. Particular care must be taken in the selection of cable, the continuity and equipotential of screens along their length, the bonding of metal parts – such as the door of a control panel and the panel’s enclosure – and the termination of cables.

Further guidance on the abatement of electrical interference can be gained from HTM 06-01.

In Part 140, LWF will discuss how the main and standby power supplies should be configured for a fire detection and alarm system in a healthcare environment. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact LWF on freephone 0800 410 1130.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.

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