ELECTRICAL SAFETY
or in open areas. In such situations, an active shielding system is the only available option. In the case of extremely sensitive medical and laboratory equipment such as scanning electron microscopes and electron lithographs, additional protection alongside a passive shielding system may be required to successfully mitigate intrusive magnetic fields. Small scale active shielding involves creating a protected zone using a cage made up of coils. A controller sends a current into the coils and produces an opposite, negative magnetic field and the fields effectively cancel each other out. The small scale active system coils can take the form of a wall mounted system or a free standing cage around the sensitive instrument itself. A more complex situation arises from the need to protect entire buildings, such as schools and medical facilities, from magnetic field radiation being emitted from nearby transmission lines or substations. Because installing a passive shielding system onto the entire side of a building is neither practical nor fiscally feasible, a large scale active system remains the only mitigation solution. Using a similar technique to the small scale active system, a free standing coil is mounted alongside the property line that produces a magnetic field of equal strength in the opposite direction, effectively redirecting the magnetic field away from the medical facility or school. As new hospitals are constructed,
project developers, consultants, engineers and medical staff frequently ask the question, “How can we increase efficiency when developing new medical facilities?” But what about existing medical facilities? Electromagnetic field surveys
conducted on site can provide immediate insight into the scope of electromagnetic field radiation in an existing structure (Figure 2). With this knowledge, retro-fit shielding systems can be designed and installed to bring existing structures up to date in terms of efficiency and optimal performance standards. To further protect the optimal performance of medical equipment in facilities, annual electromagnetic field surveys can help to prevent potential problems due to intrusive magnetic fields.
Conclusion Technology has been at the forefront of medical facility efficiency, advancement and reliability. However, as technology is continuously advancing and improving the quality of healthcare, our reliance on this technology ultimately increases alongside it. As a result, protection from intrusive electromagnetic fields that have the potential to jeopardise the optimal running of medical facilities should be taken seriously and addressed during the early design stages.
58
9ft
6ft
3ft
Electromagnetic field levels (mG) High mG
Low mG
Figure 2. Graphical representation of electromagnetic field finite element analysis simulation field survey. Graphical representations of data collected during an electromagnetic field survey can provide immediate insight into the scope of electromagnetic field radiation in an existing structure. This allows for the development of the most effective mitigation solution to be designed and installed.
After the proposed electrical equipment is finalised, the strength and extent of its magnetic field can be modelled and superimposed onto architectural drawings, immediately depicting what areas of the medical facility will meet GOS requirements for electromagnetic field levels in new medical facilities. From there, mitigation strategies can be discussed and implemented to protect the optimal running of medical facilities. Furthermore, alongside other annual maintenance procedures, electromagnetic field surveys can be undertaken to verify that electromagnetic field levels remain within acceptable limits.
Whether it is simply rearranging the location of patient care rooms and procedural areas where sensitive medical equipment is used or installing an electromagnetic shielding system to eliminate the intrusive magnetic field in its entirety, the consequence of electromagnetic field interference in medical facilities will vary. It could be as simple as an unforeseen ‘blip’ on a monitor or as serious as the delay of an audible alarm or migration of a device that leads to an interruption in patient care. Implementing effective electromagnetic field exposure prevention and mitigation solutions gives patients, their families and healthcare professionals, peace of mind that the optimal performance of the medical facilities we depend on are protected from potentially harmful electromagnetic fields.
References 1 World Health Organization. (2005) Electromagnetic Fields and Public Health: Intermediate frequencies (IF). [
www.who.int/peh-emf/publications/facts/ intmedfrequencies/en/].
2 International Agency for Research on Cancer. (2011) IARC Classifies Radiofrequency Electromagnetic Fields as Possibly Carcinogenic to Humans. [
www.iarc.fr/en/ media-centre/pr/2011/pdfs/pr208_E.pdf].
3 Canada H. (2015) Safety Code 6: Health Canada’s Radiofrequency Exposure Guidelines –
Canada.ca. [
www.canada.ca/en/ health-canada/services/environmental- workplace-health/reports-publications/ radiation/safety-code-6-health-canada- radiofrequency-exposure-guidelines- environmental-workplace-health-health-
canada.html].
4 Toronto Public Health. (2008) An Assessment of Health Implications Associated with Exposures to Electromagnetic Fields in and next to Hydro Corridors in the City of Toronto. [
www1.toronto.ca/city_of_toronto/toronto_ public_health/healthy_public_policy/hphe/ files/pdf/emf_backgrounder.pdf].
Further reading l National Cancer Institute. (2016) Electromagnetic Fields and Cancer. [
www.cancer.gov/about-cancer/causes- prevention/risk/radiation/electromagnetic- fields-fact-sheet].
IFHE
l Witters D. (2000) Medical Devices and EMI: The FDA perspective. [
www.fda.gov/ MedicalDevices/
ucm106367.htm].
IFHE DIGEST 2018
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