|emergency = siren|
|A loud noise maker, such as an air raid siren or a tornado siren.|
|Used on these elements|
|Status: de facto|
|Tools for this tag|
An outdoor warning siren (also known as a civil defense siren, air-raid siren, or tornado siren) is a loud noise maker used to deliver emergency alerts to the public, especially for fast-developing weather events such as tornados. Other common uses of sirens include summoning firefighters to a fire station or alerting the public about a tsunami, chemical spill, earthquake, or impending airborne attack.
There are two general types of outdoor warning sirens, based on the mechanism used to generate the warning tones. A pneumatic siren is powered by either a hand crank (mechanical) or an electric motor (electromechanical). An electronic siren uses electric circuitry to emulate the sounds of a pneumatic siren or to deliver voice messages, similar to a public address loudspeaker.
A siren may be mounted on a pole (similar to a power=pole) or on the roof of a building. A rotating siren produces sound in one direction at a time, relying on a motor to rotate a single horn in a circle, while an omnidirectional siren produces sound in every direction simultaneously through the use of multiple horns.
How to map
Map the siren as a node and tag it emergency=siren. If it is mounted atop a pole, also tag it man_made=mast tower:type=siren support=pole. If it is mounted on a rooftop, tag it location=roof support=roof. If it is connected to an overhead power line, connect the siren to a power=line way.
- siren:purpose=* - add here the specific use case, if valid, e.g. tornado/storm/air_raid/civil_defense, optional
- siren:type=* - pneumatic, electronic, or electromechanical, optional
- siren:range=* - range of audibility, e.g. 1000, like usual Units format, optional
- siren:model=* – manufacturer name and model number
- manufacturer=* and manufacturer:wikidata=*
- height=* – height of mounted siren
- operator=* – name of the entity that maintains or is responsible for sounding the siren
- direction=* – if the siren is directional, the direction in which the horn or horns are pointed, e.g. NE (northeast)
Outdoor warning sirens are often found near major factories, power plants, and dams.
In the United States, outdoor warning sirens are strongly associated with Tornado Alley but may also appear elsewhere. An urban county may lay out its outdoor warning sirens in an approximate grid. By contrast, a rural community may place its siren near a place where people are likely to be outdoors, such as a park or school, or near existing emergency communications equipment, such as at a fire station, police station, water tower, broadcast antenna, or power substation. It was previously common for sirens to be mounted atop the hose tower of a fire station (tower:type=hose), but increasingly sirens are mounted atop ordinary utility poles near the street for easier maintenance.
In aerial imagery, pole-mounted sirens are easy to confuse with pole-mounted power transformers (power=pole transformer=*) and flagpoles (man_made=flagpole) at all but the highest zoom levels, so confirm the siren in street-level imagery if possible.
OSM Emergency Map renders sirens with icons at zoom level 11 and above (example).
- Air Raid Sirens Wiki – useful for identifying the model from aerial or street-level imagery
- Gallery of (mostly American) siren models and manufacturers – Wikidata Query Service