OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

January 23, 1991

Mr. David A. Kruger
GAI-Tronics Corporation
P.O. Box 500228
Houston, Texas 77250-0228

This is in response to your letters of May 31, 1990, (addressed to the Occupational Safety and Health Administration (OSHA) Regional Office in Dallas, Texas) and of September 29, 1990, addressed to the OSHA National Office, concerning the requirements of the OSHA standard at 29 CFR 1910.165, which pertains to employee emergency alarm systems. In your earlier letter, you had a series of questions that pertained to this standard, and the following paragraphs will hopefully address your concerns. We apologize for the delay in our response.

With respect to 1910.165(b)(2) you requested clarification of the word "perceived." OSHA interprets "perceived" to mean employees shall be able to hear, see, or feel an alarm signal to the extent necessary to understand what it means. If an establishment uses an alarm system that uses sound as a means of signaling its employees, then the sound must be loud and clear enough to be understood by all employees of that establishment, irrespective of where the employees are located within the establishment. Employees must understand the meaning of each such alarm signal. There may be instances where establishments have alarm systems with loudspeakers installed in such a manner that employees may hear the alarm but cannot understand the signals because the same signals are coming from other parts of the plant. Such instances (where employees may get confused because of loudspeaker arrangement) will not meet the requirements of the standard.

Your second question pertained to 1910.165(b)(3), specifically, with respect to the phrase, "to perform actions designated under the emergency action plan," contained in this standard. After an employee becomes aware of an emergency situation, the next step involves actions to be performed by that employee. Generally, the actions include evacuation, or emergency response to mitigate an emergency situation. The alarm need not announce by voice the actions to be taken by employees. However, under the requirement of this standard, when employees become aware of an emergency condition, they shall follow and perform the actions for which they have been trained under their emergency action plan. For instance, some employees under their emergency actions plan may evacuate the plant in a safe manner, and some may be required to participate in actions responding to emergency.

In response to your third question, which pertained to 1910.165(b)(4), we interpret that the method by which priority is given to emergency messages over non-emergency messages (where a communication system also serves as the employee alarm system), could be either by manual or by automatic systems.

Your next question related to the first sentence of 1910.165(c)(1), that pertains to approval of the emergency equipment. The term "approved" used in this standard means that the equipment is listed or approved by a nationally recognized testing laboratory (NRTL) described in the OSHA standard at 29 CFR 1910.7. At present, OSHA recognizes [19] NRTL's. You may contact them at the addresses given in the enclosed list. [Or see the
Nationally Recognized Testing Laboratory web page.]

The fifth question pertained to the second sentence of 1910.165(d)(3). Your question was: "Does the back-up means of alarm need to meet the requirements of the primary means of alarm?" The back-up means of alarm is not required to meet all of the primary means; however, it must be capable of effectively providing alarm service equivalent to the primary means. The standard gives examples of other means of alarms that may be used when the primary systems are out-of-service. In other words, the back-up system need not be a duplicate of the primary system.

Your final question was related to the first sentence of 1910.165(d)(4). This sentence of the standard requires that the systems that are "capable" of being supervised are supervised. This standard does not require that all employee alarm circuitry installed after January 1, 1981, be capable of being supervised. However, if certain systems installed have the capability of being supervised, then only those systems need to be supervised. Please refer to Appendix A of 1910.165 for examples and a variety of ways that may be used to continuously monitor the system to assure it is operational and to identify trouble in the system and give a warning signal.

In your second letter you questioned the use of tone only systems and their applicability to larger chemical plants. You described scenarios where employees may have to go through the contaminated areas in order to reach a designated "muster area" or may walk into a hazard if the nearest phone happens to be in the wrong direction. Your question with regard to tone only systems is: "Given the restraints of radio and phone, how does a tone only system comply with the requirement of the standard?

During an OSHA inspection, if it is determined through employee interviews that they are not trained to perform proper actions, such as walking away from contaminated areas (that is to walk upwind from the contaminated areas) in order to either use a phone or to evacuate the area, then citations may result for violation of the OSHA standards, particularly of [1910.38], 1910.120(l) and 1910.120(q). Employers may choose tone only systems, among other alarm systems, provided their employees are trained to take appropriate actions.

Your letters requested for each of the above questions, whether your system would meet OSHA requirements, if they are installed to meet all OSHA requirements contained in 1910.165. Although safety features of the alarm systems described by you seem to meet our requirements, OSHA neither approves nor endorses any products, since the products may be mis-applied during installation, or misused during their usage. Therefore OSHA cannot guarantee the reliability of your systems nor can we accept its functionality, unless the systems are assessed on a case-by-case basis through employee and management interviews at the site of and after installation.


Patricia K. Clark, Director
[Directorate of Enforcement Programs]

[Corrected 6/2/2005]