Question:
Electrostatic discharges (ESD) cause malfunctions and damages to industrial equipment and consumer electronics. Accordingly, ESD may affect the functionality and reliability of medical equipment. Due to the rapid technology development, interference to sensitive instrumentation could be critical for patient safety in hospitals. Do organizations in healthcare have electrostatic control and are there any reasons to be concerned?
Answer:
Without the control, static electricity and ESD can cause serious hazards to human safety in healthcare. Medical instruments and data processing equipment can be susceptible to ESD, especially when electromagnetic compatibility does not cover the complete system of instrumentation. ESD immunity testing based on a human metal connection ensures safety, but all the possible combinations of instruments with data processing and audio-visual systems are not necessarily tested. Disruptions and damages have been reported over recent years, but in most cases root causes of the ESD failures cannot be traced. ESD malfunctions and damages are generally classified as unknown electric failures.
Unprotected electronic devices are susceptible to electrostatic discharge. First, ESD control is essential in the manufacturing of medical equipment. Precautions must also be taken in maintenance and service, for example during the replacement of ESD sensitive devices such as discrete components or printed circuit board assemblies. Service and maintenance organizations in healthcare must develop an ESD control program in accordance with ANSI/ESD S20.20 or IEC 61340-5-1.
Secondly, malfunction or disturbance of medical equipment is not the only reason to control static electricity. Avoidance of electrostatic attraction (ESA) decreases airborne microbe contamination and improves overall cleanliness in healthcare. Without the control, increased deposition of microorganisms onto charged surfaces can contribute to the incidence of hospital infections.
Third reason to control static electricity is prevention of ignition of flammable gases, liquids and other materials. The use of flammable substances in healthcare facilities has decreased, but without the control, the risk of fires and explosions can still occur especially in laboratories, intensive care units and operating rooms.
Fourth concern is an electrostatic shock to people. ESD energy can be high enough to cause painful sensations to patients and healthcare personnel, resulting in involuntary movements, which can lead to accidents. Figure 1 shows an electrostatic discharge captured from the patient bed. In this example, electric potential of the bed was 14000 V and the discharge energy integrated over 1500 Ω human body resistance was approximately 20 mJ.
The risk of electrostatic hazards can be reduced to tolerable levels by grounding of personnel and other conductors, and by correct selection of materials. Several members of the ESD association joined the project team of technical committee of International Electrotechnical Commission TC 101 “Electrostatics” in 2015 to make hospitals safe and free from electrostatic hazards. The project team had 27 experts from ten different countries. In September 2018, IEC published the new international standard: IEC 61340‑6-1:2018, Electrostatic control for healthcare – General requirements for facilities.
Electrostatic control requirements in healthcare depend on the medical procedures, locations and activities. Grounding of personnel and other conductors is required in locations, where temporary losses of functions of medical equipment pose a significant risk to the life of patients. Electrostatic control can also be required in other medical locations depending on medical treatment or on manufacturer’s specifications of medical equipment. A selection of the materials to reduce residual charge levels is recommended in all locations.
End note: When electrostatic control is properly considered and implemented, there is no need to worry about electrostatic hazards in healthcare. To ensure safety, it is important to comply with the standards during service and maintenance and when new hospitals are built or when construction work is planned.
References
- M. Kohani and M. Pecht, Malfunctions of Medical Devices Due to Electrostatic Occurrences, Big Data Analysis of 10 Years of the FDA’s Reports, IEEE Access, March 9, 2018
- ANSI/ESD S20.20-2014 For the Development of an Electrostatic Discharge Control Program for –Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices)
- IEC 61340-5-1:2016, Protection of electronic devices from electrostatic phenomena – General requirements
- Viheriäkoski T., Kokkonen M., Tamminen P., Kärjä E., Hillberg J., Smallwood J., Electrostatic Threats in Hospital Environment, ESD Association, EOS/ESD symposium 2014
- IEC 61340-6-1:2018, Electrostatic control for healthcare – General requirements for facilities
Toni Viheriäkoski completed his technical supervisor studies in information technology in 1994 while working in Nokia Networks. After establishing a calibration and electrostatics laboratory services for Nokia, he transferred to Nokia Siemens Networks in April 2007 where he continued his work as an electrostatics specialist and senior sourcing engineer until he moved on to his own company, Cascade Metrology Oy, which was previously established in 2005. Toni received iNARTE ESD engineer certification in 2004. Currently, he is working in the field of electrostatics and ESD risk analysis for healthcare, medical, electronics, automotive and process industries.
Toni has written more than 30 publications related to electrostatics or ESD. He has been a chair of the Finnish STAHA Association since 2006. He was nominated a chair of the Finnish Standardization Committee SK101 in 2016. He is a member of WG17 and WG25 of EOS/ESD Association, WG5 of IEC TC101 and a project leader of IEC PT 61340-6-1.
Toni can be reached at +358 44 5688 599 or toni.viheriakoski@esdcafe.fi.
