Civil Defense Sirens of O'ahu

Aloha & welcome to!

I created this website to share information about O'ahu's outdoor warning system. Despite my extensive knowledge of Oahu's siren system, I'm not affiliated with the local emergency management agency. This website, including all of it's content, was created on my own personal time.

A brief history of Oahu's siren system...

Since the mid 20th century, large outdoor warning sirens were installed across the state of Hawai'i. These sirens are used to warn the public of all natural & man made disasters. At the end of the 20th century, Hawai'i began replacing their cold war era "legacy" sirens with newer models. Despite the extensive systemwide upgrades, a handful of legacy sirens still remain within the system today. These legacy sirens are mostly EOWS, Thunderbolt & Thunderbeam variants, all produced by Federal Signal Corporation. All of Hawai'i's active legacy sirens have been upgraded with cellular & satellite antennas. The entire statewide siren system is controlled via cellular/satellite, Hawai'i no longer uses VHF radio for activation. The newer, modernized sirens feature battery backup, and are capable of operating without grid power. Almost all of the new sirens currently being installed in Hawai'i are Modulator 6024B's, manufactured by Federal Signal. Most of the newer sirens in Hawai'i are painted green, especially on O'ahu. However, some older sirens are still painted yellow from the cold war "civil defense' era. There are also a handful of sirens that are painted brown, and a select few that are painted white.

All outdoor warning sirens in Hawai'i are tested on the first business day of each month. During this test, all sirens will sound a steady "alert" tone for 1 minute. After the monthly alert signal test, the sirens within Campbell industrial park's hazmat zone will also test the hazmat "whoop" tone. This whooping tone is used to notify the public of a hazmat emergency within the Campbell industrial park area, such as a chemical spill. The whoop tone can also be used for various other hazmat emergencies across the state, such as volcanic activity warnings. In the event of a national emergency, the wailing "attack' tone will be used to notify the public. The wailing attack warning signal is reserved for national emergencies only, and this signal is not tested during regular monthly testing. O'ahu is also home to several military installations. Each installation has it's own siren system, but most installations test their warning sirens alongside the state system every month. 

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