Test is normally on the first Wednesday of the month at noon. In an actual emergency, those hearing the siren should shelter indoors to avoid potential harm from an ammonia release.

Bayer Biopharmaceutical in West Berkeley will test their emergency siren for ammonia gas this afternoon, March 27, 2023 – a change from their normal testing at noon on the first Wednesday of the month.
While there is no action required of the public for this ammonia siren test, it’s important to know the sound of the siren, the regular Wednesday at noon test schedule, and that an emergency would require those in the immediate area to shelter indoors.
Bayer is required to notify the area west of San Pablo Avenue and south of University Avenue to the Emeryville border. Bayer has sent postcards to affected residents and emails to those who opted in to receive updates about community meetings.
Bayer uses ammonia in its refrigeration system, which the company says has many safeguards to prevent an unsafe off-site release. The company says no such release has ever happened in Berkeley.
In the unlikely event of a significant accidental release, ammonia can pose significant health risks if contact is made or it is inhaled at a concentration above 25ppm.
Know the siren sound, how to respond
The siren has a loud wailing noise that slowly alternates between a low and a high pitch. The siren is accompanied by a male voice giving instructions to either shelter in place or indicating a test mode.
Typically, if you hear this siren at any time other than noon on the first Wednesday of the month, or if the siren’s verbal message directs you to shelter in place, treat this as an emergency situation:
Take these actions:
- Take shelter indoors
- Close all doors and windows
- Turn off any thermostats in use
- If you are outside, quickly move inside
- Stay inside until informed it is safe to go outdoors
While the March 27, 2023 test of the ammonia siren requires no action, knowing these steps is critical for an emergency.
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