FAQ [Health Devices Sep 1996;25(9):347]

Hospital: What is an acceptable leakage current limit for electronic devices (e.g., personal computers) used in non-patient-care areas, such as a nurses station?

ECRI: Devices used outside the patient care vicinity, including nurses stations and the clinical laboratory, should adequately ensure staff safety. Grounding or double insulation is preferred, but household, office, or maintenance appliances that are not commonly equipped with grounding or double insulation can be used. ECRI recommends that leakage currents not exceed 500 microamperes; however, we recognize that this limit is not always practical. Leakage currents up to 3,500 microamperes may be considered appropriate where no special requirements or risks exist—for example, in situations where the user is not likely to be grounded or where contact with conductive surfaces that could become energized is not likely.

Although leakage currents as high as 3,500 microamperes may be felt, or even cause an involuntary reaction, they are allowed in some standards applicable to nonmedical products. For example, an American National Standards Institute (ANSI) standard, ANSI C101-1992, which applies to household items (including computers), specifies a leakage current of 500 microamperes for portable appliances that can be moved from one place to another within the home. However, an exception allows leakage currents of up to 3,500 microamperes, under some circumstances, for devices that require electromagnetic-interference-suppression (EMI-suppression) filtering to comply with Federal Communications Commission (FCC) regulations.(1) The second edition of an Underwriters Laboratories (UL) standard, UL 1950, allows up to 750 microamperes for handheld equipment and up to 3,500 microamperes for portable and stationary equipment.(2)

Notes

1. American National Standards Institute. American national standard for leakage current for appliances. Northbrook (IL): Underwriters Laboratories; 1992. ANSI C101-1992.
2. Underwriters Laboratories (UL). Safety of information technology equipment, including electrical business equipment. 2nd ed. Northbrook (IL): UL; 1993. UL 1950.