Emergency Standards » Employee Alarm Systems

The purpose of the employee alarm systems standard is to reduce the severity of workplace accidents and injuries by ensuring that alarm systems operate properly and procedures are in place to alert employees to workplace emergencies. [29 CFR 1910.165]

This section will help you to understand alarm system requirements for warning employees when a hazardous condition or event occurs.

OSHA's employee alarm systems standard applies to all employers that use an alarm system to satisfy any OSHA standard that requires employers to provide an early warning for emergency action, or reaction time for employees to safely escape the work place, the immediate work area, or both. [29 CFR 1910.165]

This standard also applies to you if an OSHA standard specifically states that you must install an employee alarm system. For example, some standards that specifically require or reference alarm systems include:

Businesspeople in a meeting

NOTE: This section applies to all emergency employee alarms installed to meet a particular OSHA standard. This section does not apply to those discharge or supervisory alarms required on various fixed extinguishing systems or to supervisory alarms on fire suppression, alarm or detection systems unless they are intended to be employee alarm systems. [29 CFR 1910.165(a)(1)]

The employee alarm system shall provide warning for necessary emergency action as called for in the emergency action plan, or for reaction time for safe escape of employees from the workplace or the immediate work area, or both. [29 CFR 1910.165(b)(1)] An employee alarm system can be any piece of equipment and/or device designed to inform employees that an emergency exists or to signal the presence of a hazard requiring urgent attention. National Fire Protection Association (NFPA) 72, National Fire Alarm Code, requires a fire alarm signal to be distinctive in sound from other signals and can not be used for any other purpose.

The two most common types of alarms are audible and visual devices.

The employee alarm shall be capable of being perceived above ambient noise or light levels by all employees in the affected portions of the workplace. Tactile devices may be used to alert those employees who would not otherwise be able to recognize the audible or visual alarm. [29 CFR 1910.165(b)(2)]

Audible Alarms:

Audible alarms include bells, horns, sirens, voice announcement systems, and other devices that can be distinguished above and apart from the normal sound level within the workplace. Temporal and voice signals are the most effective means.

  • Use temporal coded signals. Temporal coding is accomplished by interrupting a steady sound in the following manner: .5 sec ON; .5 sec OFF; .5 sec ON; .5 sec OFF, in a repeating cycle.
  • Use a distinctive three-pulse temporal pattern to signal an immediate emergency evacuation.

    Standard Audible Emergency Evacuation Signal. This signal shall consist of a "three-pulse" temporal pattern. Three successive "on" phases, lasting 0.5 second each, must be separated by 0.5 second of "off" time. Then, at the completion of the third "on" phase there must be 1.5 seconds of "off" time before the full cycle is repeated. Therefore, the total cycle shall last 4.0 seconds (0.5 second "on," 0.5 second "off," 0.5 second "on," 0.5 second "off", 0.5 second "on," 1.5 seconds "off"). [S3.41, Audible Emergency Evacuation Signal, American National Standard Institute (ANSI)]

  • Only use this signal pattern to notify personnel of the need to immediately evacuate the building. Total evacuation is not always desirable or necessary during an emergency therefore there should be a different signal pattern assigned to signify the need for relocation of the occupants from the affected area to a safe area within the building or for a "shelter in place".

NOTE: Audible notification devices such as horns, bells, or sirens are no longer recognized for new systems by NFPA 72, National Fire Alarm Code – only temporal signals or voice signals. For visual signals, only strobe lights are now recognized by NFPA 72 and the Americans with Disabilities Act (ADA). The following bells, horns and sirens, are only permitted in existing systems.



Vibrating bells are the most common signal device. Bells are commonly used in schools for fire alarms.



Horns produce a very loud distinctive sound that immediately attracts attention. Horns can be useful to call attention to critical situations. Signals other than those used for evacuation purposes do not have to produce the temporal coded signal.



Sirens produce a loud piercing wail that makes them ideally suitable for initiating a site-wide evacuation.

Portable Radio

Workplace Announcement System:

Speakers can be used to play a live or recorded voice message. They are often ideally suited for large workplaces where phased or guided evacuations are needed.

Visual Alarms:

Visual alarms use steady, flashing, or strobe lights to alert workers to an emergency situation in areas where noise levels are high, especially where ear protection must be worn and audible signals may not be heard or may be misunderstood. Visual signals also provide an effective way to alert workers with hearing loss about an emergency. Strobe lights are recognized as the most effective means. Only strobe lights are now recognized by NFPA 72 and the Americans with Disabilities Act (ADA).

Provide visible signals in restrooms, in other general and common use areas, and in hallways and lobbies. Common use areas also include:

  • Meeting and conference rooms,
  • Classrooms,
  • Cafeterias,
  • Filing and photocopy rooms,
  • Employee break rooms,
  • Dressing, examination, and treatment rooms, and
  • Similar spaces that are not used solely as employee work areas. [Americans with Disabilities Act Accessibility Guidelines, ADAAG 4.28.1 General].

NOTE: It is not always possible to fix the occupancy of a room or space or anticipate its use by a person with a hearing impairment. Visual alarms are particularly important in those common use spaces where a person may be alone.

Strobe Light

Flashing/Steady Lights:

Speakers can be used to play a live or recorded voice message. They are often ideally suited for large workplaces where phased or guided evacuations are needed.

Flashing light

Strobe Lights:

Strobe lights use high intensity flash tubes that are ideally suited for areas where high ambient light levels make traditional rotating or flashing lights difficult to distinguish or where ambient noise makes audible signals difficult to hear.

For an alarm system to be effective, you must have an emergency action plan that addresses how employees, including disabled workers, will be informed that an emergency exists and how they should respond. The alarm system must inform all affected employees that an emergency exists and what their immediate response should be based on the alarm sequence. This plan should include:

  • The preferred means of reporting emergencies, such as manual pull box alarms, public address systems, radio or telephones. The employer shall post emergency telephone numbers near telephones, or employee notice boards, and other conspicuous locations when telephones serve as a means of reporting emergencies. Where a communication system also serves as the employee alarm system, all emergency messages shall have priority over all non-emergency messages. [29 CFR 1910.165(b)(4)]
  • Procedures for sounding emergency alarms in the workplace. For those employers with 10 or fewer employees in a particular workplace, direct voice communication is an acceptable procedure for sounding the alarm provided all employees can hear the alarm. Such workplaces do not need a back-up system. [29 CFR 1910.165(b)(5)]
  • A current list of key personnel, such as the plant manager or physician, in order of priority, to notify in the event of an emergency during off-duty hours.

For alarm systems to provide adequate notification in the event of an emergency, the employer shall assure that all devices, components, combinations of devices or systems constructed and installed to comply with this standard are approved. Steam whistles, air horns, strobe lights or similar lighting devices, or tactile devices meeting the requirements of this section are considered to meet this requirement for approval. [29 CFR 1910.165(c)(1)]

The employer should assure that the alarms which are installed are:

  • Capable of being heard, seen, or otherwise perceived by everyone in the workplace. [29 CFR 1910.165(b)(2)]
  • Distinctive and easily identified by all employees as a signal to evacuate the work area or perform actions identified in your emergency action plan, such as "shelter-in-place". [29 CFR 1910.165(b)(3)]
  • Supervised if they were installed after January 1, 1981 and contain circuitry that is capable of being supervised. These systems must also provide positive notification to assigned personnel whenever a deficiency exists in the system. [29 CFR 1910.165(d)(4)]

Alarm Selection Guidelines:

Did You Know?

Research indicates high-intensity xenon strobe lamps to be the most effective and white light the most discernible. Colored lamps, particularly red, were found to be ineffective even at very high intensities.

To get the most from an alarm system, follow these guidelines when selecting devices:

  • Make sure the alarm's sound is as different from the background noise and light as possible. Audible alarms should exceed the ambient noise level by at least six decibels. The light intensity for visual alarms should be at least 75 candela.
  • Use alarms with integrated audible and visual signals to accommodate the hearing and visually impaired, and for areas where a person may be working alone. This includes areas such as restrooms, storage areas, offices, and similar areas. (These devices are available for about the same cost as an audible or visual signal alone).
  • Avoid using strobe devices that flash at rates above five flashes per second (fps). Rates above five fps can trigger seizures in people with certain forms of epilepsy. When multiple devises are used, either synchronize or reduce their flash rate so that the combined rate does not exceed five fps.

Protection of Alarms:

To make sure devices stay operable, follow these guidelines:

  • Alarm system components that may be exposed to corrosive environments should be either made or coated with a non-corrosive material.
  • Position alarm devices away from or out of contact with materials or equipment which may cause physical damage.
  • Alarms that are installed outdoors and need to be shielded from the weather to work properly must be protected with a canopy, hood, or other suitable device.
  • All devices should be securely mounted to a solid surface, such as screwed to a junction box with a mounting plate or other appropriate method that prevents them from putting pressure or stress on attached wires or tubing.

Alarm Placement Guidelines:

To ensure your alarm system provides adequate coverage, follow these guidelines when placing alarm devices:

  • Put at least one visual alarm in each room and any other general usage areas (guest restrooms, meeting rooms) which may be occupied by those with hearing impairments. You may need more than one alarm per room for those that exceed the manufacturer's spacing requirements. For example, if your alarm is rated for 50 feet, install alarms so they are evenly spaced with no more than 50 feet between devices.
  • Mount visual and audible devices 80 inches above the highest floor level within the space or six inches below the ceiling, whichever is lower.
  • Manually activated devices for use in conjunction with alarms must also be:
    • Unobstructed, conspicuous, and readily accessible. [29 CFR 1910.165(e)] Make available an emergency communications system such as a public address system, telephone, portable radio unit, or other means to notify employees of the emergency and to contact local law enforcement, the fire department, and others. [29 CFR 1910.165(b)(4)]

Employee alarm systems are important life safety devices and must be maintained in an operating condition at all times except during repairs or maintenance. [29 CFR 1910.165(d)(1)]

Routing Test and Maintenance:

  • Test the reliability and adequacy of non-supervised employee alarm systems every two months. Use a different actuation device in each test of a multi-actuation device system. [29 CFR 1910.165(d)(2)]
  • Maintain or replace power supplies as often as necessary to ensure a fully operational condition. Provide a back-up means of alarm when systems are out of service, such as employee runners or telephones. [29 CFR 1910.165(d)(3)]
  • Use properly trained persons to service, maintain, and test employee alarms. [29 CFR 1910.165(d)(5)]
  • Do a visual check to ensure that employee alarm devices are not obstructed/installed in a manner that would prevent sound or light from reaching or entering the protected areas.
  • Restore all employee alarm systems to normal operating condition as soon as possible after each test or alarm. Spare alarm devices and components must be readily available in sufficient quantities and locations for prompt restoration of the system. [29 CFR 1910.165(c)(2)]

Employees must know what types of emergencies may occur and what course of action they must take. Make sure all your employees understand the function and elements of your emergency action plan, including types of potential emergencies, reporting procedures, alarm systems, evacuation plans, and shutdown procedures. Discuss any special hazards your workplace may have such as flammable materials, toxic chemicals, radioactive sources, and/or water-reactive substances. Your training should address the following:

  • Individual roles and responsibilities.
  • Threats, hazards, and protective actions.
  • Location and operation of manually activated pull stations and communication equipment.
  • Emergency response procedures.
  • Evacuation, shelter, and accountability procedures.
  • Location and use of common emergency equipment.
  • Emergency shutdown procedures.

When your employees know how to sound an alarm and/or notify emergency personnel at the first sign of an emergency, it may make the difference between life and death.