A few years ago, Underwriters Laboratories (UL) gave medical power-strip manufacturers new guidelines regarding the approval of power strips for medical use. Essentially, UL said medical power strips approved under standards UL 544 or UL 2601-1 were no longer eligible to carry the UL mark for medical use. Furthermore, power strips approved under UL 1363 or UL 1449 could not be referenced as appropriate for medical applications, even if they were using medical-grade sockets. UL thinking was that power-strip manufacturers using these approvals and references for medical use were misleading the public into thinking the items were medically approved and acceptable for use under UL medical guidelines. At the time, this left the market empty of medically-approved power strips and left some medical-equipment manufacturers suddenly looking for alternatives that would meet the new requirements.

Requirements

A power strip with medical approval under the new UL guidelines must meet:

• Approval to one or more of the following safety standards: UL 60601-1, IEC 60601-1-1, EN 60601-1, CAN/CSA C22.2 No.601-1-M90, CAN/CSA C22.2 No.601.1S1-94, and CAN/CSA C22.2 No.601.1B-98

• On NEMA strips, look for outlet covers that can only be opened with the use of tools (for patient safety), as required by UL to prevent the inadvertent connection of equipment with standard plugs by unqualified personnel.

• Verify that leakage current and other critical specifications meet both medical standards and your requirements. If there are no leakage-current specifications, the strips may not be approved for medical use.

Medical cords

Several characteristics qualify cords used with North American medical equipment as hospital-grade. For one, the plugs are subject to special requirements from several standards:

• Medical equipment standards UL 60601 and CAN/CSA C22.2 no 60601-1

• Power supply cord standards UL 817 and CAN/CSA C22.2 no 21

• Attachment plug standards UL 498 and CAN/CSA C22.2 no 42

Second, hospital-grade plug patterns must conform to the NEMA 5-15 standard. However for hospital-grade patterns the blades are usually solid, instead of folded brass, and nickel plated. And the plug normally includes a cable retention device or strain relief to prevent stress on the plug's internal connections.

And lastly, it is imperative that the ground connection be reliably maintained to protect patients and medical staff. Although many hospitals prefer a clear plug so internal connections can be visually inspected, UL and CSA standards do not mandate clear plugs nor do they provide any restrictions on color. In fact, hospital-grade plugs and cords are frequently gray.

Leakage current

Leakage current flowing between line and ground in electrical equipment can, under certain circumstances, present a lethal shock hazard to users. The shock hazard usually depends on the amount of leakage current, accessibility of a “hot” surface to the user, and whether or not the user is well grounded. The susceptibility of a patient to serious injury or death increases with patient-connected medical equipment. The hazard comes from the low impedance path between patient and equipment, and the high probability that the patient will complete the fault circuit.