Emergency Warning Sirens

Emergency Alert Siren[1]
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Sirens are still the most effective method to warn the population at large in the shortest amount of time. People who may be outdoors at ball games, in their yard, or anywhere else where they are not in contact with the normal news media channels such as radio, TV or local public address systems.

In the United States, there is no national level alert system. Normally, sirens are controlled on county or local level, or, in Hawaii, on state level. Sirens are usually used to warn of impending natural disasters, as well as threats of military attacks, which in the United States are rare. To find out your community’s siren policy, check with the local emergency management agency. Here are some examples that sirens are used:

Throughout the Great Plains, Midwest, and South, they are used to warn the public to take cover when a tornado warning is issued.

Emergency alert sirens are generally required in areas within a ten-mile radius of nuclear power plants.

Coastal communities, especially in northern California, Oregon, Washington, Alaska, and Hawaii use siren systems to warn of incoming tsunamis.

In the South and East Coast (except from Texas, Maine and New Hampshire), they use sirens to inform people about approaching hurricanes.

In Pierce County, Washington there is a system of sirens set up along the Puyallup and Carbon River valleys to warn residents of volcanic eruptions and lahars from Mt. Rainier.

Some U.S. volunteer fire departments, particularly in rural areas, use sirens to call volunteers to assemble at the fire house, but to a decreasing degree than in years past due to technological advancements. Some areas utilize their sirens as a last resort, relying more on cellular and paging technology; however, a decreasing number of rural brigades are outside the range of wireless communications and rely on sirens to activate the local volunteer brigade.

Many college campuses in the U.S., especially in the wake of the Virginia Tech shooting, have begun installing sirens to warn students in the event of dangerous incidents. Here is FEMA list of emergency communications plans from campuses of various sizes, case studies and lessons learned, and guidelines which may be relevant to emergency preparedness planning.


Federal Standard Usage

Emergency alerts sirens, commonly know as a civil defense siren (also colloquially referred to as an air raid or tornado siren), were initially designed to warn of air raids in World War II, they were adapted to warn of nuclear attack and of natural phenomena such as tornadoes.

The U.S. Federal standard regarding air raid signals is defined in FEMA’s Outdoor Warning Systems Guide, CPG 1-17, which describes the Civil Defense Warning System (CDWS) and its warning signals. The language was slightly revised by FEMA’s National Warning System Operations Manual 1550.2:

The U.S. Federal siren standards are as follows:[2]

  • Attack Warning – A 3 to 5 minute wavering tone on sirens or a series of short blasts on horns or other devices. The “Attack Warning” tone is the iconic, rising-falling sound of an air raid or nuclear attack, frequently heard in war movies. It was once reserved for imminent enemy attack, but is today sometimes used to warn of severe weather, tsunamis, or even fire calls, depending on local ordinance.
    (Click to hear a “wavering tone”.)
  • Attention or Alert Warning – A 3 to 5 minute steady continuous tone from sirens, horns, or other devices. Local government officials may authorize use of this signal to alert the public of peacetime emergencies. The “Alert Warning” is widely used by municipalities to warn citizens of impending severe weather, particularly tornadoes. This practice is nearly universal in the Midwest, where intense and fast moving thunderstorms occur frequently. In seaside towns, the “Alert” may also be used to warn of a tsunami.
    (Click to hear a “steady tone”.)
  • A third distinctive signal may be used for other purposes, such as a local fire signal. There is no standard “Fire” signal in the United States, and while the use of sirens by volunteer fire departments is still common, it is diminishing.

Many cities in the U.S. periodically sound their sirens as a test, either weekly, monthly or yearly, at a day and hour set by each individual city.



  1. Image Source: http://en.wikipedia.org/wiki/File:Federal_Signal_Thunderbolt_1003_head.jpg [Accessed April 10th, 2013]
  2. FEMA – National Warning System Operations Manual 1550.2: http://www.fema.gov/pdf/library/1550_2.pdf