Cause of Device-Related Incident
External factors

Clinical Specialty or Hospital Department
CCU / ICU / NICU; Clinical/Biomedical Engineering; Continuing Care; Nursing

Device Factors
*Not stated

Document Type
User Experience Network (UEN) reports

External Factors
Medical gas and vacuum supplies

Mechanism of Injury or Death

Support System Failures
*Not stated

Tampering and/or Sabotage
*Not stated

User Errors
*Not stated

Nurse Call Systems [15-614]; Pillow Speakers [17-198]

Use of Nurse Call Pendants and Pillow Speakers by Patients Receiving Oxygen Therapy

User Experience Network™ [Health Devices Dec 1996;25(12):477-9]


Our nurse call pendants and pillow speakers bear a notice stating that they are not to be used in locations where oxygen is being administered. We understand that other institutions are permitting patients who are receiving oxygen to use these controls. What should we do?


An oxygen-enriched atmosphere (OEA) is an atmosphere in which the concentration of oxygen exceeds 23.5% by volume. A high-concentration OEA (often approaching 100% oxygen) normally exists in an oxygen tent, croup tent, incubator, oxygen hood, or similar device. In such locations, the use of nurse call pendants and pillow speakers may be a concern. However, these devices are most likely to be used in lower-concentration OEAs—specifically, in or near the "site of intentional expulsion" (SIE) of oxygen from an oxygen-administration device such as a nasal cannula or a face mask. NFPA 99-1996 defines an SIE as "all points within 1 ft (0.3 m) of a point at which an oxygen-enriched atmosphere is intentionally vented to the atmosphere" (Section 2.2).

We believe that the fire risk posed by nurse call pendants and pillow speakers (and other low-voltage control pendants) is very low in the most common applications, even if the pendant is brought within the 1 ft zone of an SIE. This is because of the low voltages and currents in the controls, the typically low probability of there being any ignitable fuels in components that are subject to arcing or sparking, and the lack of hot components in these devices. Moreover, although many institutions are presumably using pendants not listed for oxygen use, we are aware of no reports of pendant-caused fires.

Some of the confusion surrounding this issue may arise from NFPA's recommendations on the subject. Section 7- of NFPA 99 states: "Electrical equipment used within oxygen delivery equipment shall be listed for use in oxygen-enriched atmospheres, or sold with the intent to be used in oxygen-enriched atmospheres." However, the 1996 edition of NFPA 99 has added a section (A-7- to its appendix stating that "the intent of 7- is to advise users to specify appliances that meet higher requirements where the hazard is higher, but not to overspecify where the hazard is minimal. Thus, as they are ordinarily used, nurse call buttons, pillow speakers, etc., do not need to be listed for use in oxygen-enriched atmospheres." In other words, when used in SIEs (not in high-concentration OEAs), these devices need not be listed for use in an OEA.

The appendix material does caution, however, that "these requirements apply only to the intended use. The user must exercise vigilance to guard against an unintended use or an accidental failure, which can vastly increase the hazard." In our opinion, NFPA 99-1996 does not intend the use of nurse call buttons or pillow speakers in areas of especially high oxygen concentration (e.g., approaching 100%), such as would be found in oxygen tents or hoods.


  1. Do not permit the use of nurse call or pillow speaker pendants in enclosed spaces having a very high concentration of oxygen, such as oxygen tents or hoods, unless the pendants are labeled for use in an OEA.
  2. Permit the use of nurse call and pillow speaker pendants in low-concentration OEAs, such as the SIE around patients receiving oxygen by nasal cannula or face mask.
  3. If you encounter applications for which you feel additional precautions are needed (for example, using speakers and pendants in areas with reduced ventilation), consider one or more of the following measures:
  • A series of curves (Figures 9-[a] through [f]) published in NFPA 99-1996 provides safe-design criteria for circuits used in OEAs. Your clinical engineering personnel may be able to determine, with the help of information from the manufacturer of your system, whether voltages and currents to which the pendants are exposed remain within the safe regions defined by these curves.
  • Tether the pendant to an object near the bed. The tethering should not be easily defeated by the patient, but should keep the pendant within the patient's reach. Properly tethered, the device will be prevented from being brought in so close that the patient might, for example, fall asleep with it near the mask or cannula. Alternatively, the pendant can be bracketed to the bedrail instead of being tethered.
  • Replace the usual control with one that is pneumatically connected (e.g., using a squeeze bulb and tubing) with switches or other electrical control devices attached to the system wall panel.
  • Determine whether the original manufacturer has specialty pendants or accessories that are approved for use in an OEA.


  • Nurse Call Systems [15-614]
  • Pillow Speakers [17-198]

Cause of Device-Related Incident

External factor: Medical gas and vacuum supplies

Mechanism of Injury or Death


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