Emergency evacuation sirens are alarms in place in most places where there is a need to warn a large number of people regarding any emergency. In some places like condos and big buildings, a form of these alarms is the fire sirens that ring to inform the resident to leave the premises due to a fire threat.
In factories and all types of businesses where employees are working in hazardous or non-hazards environment, it is the liability of the company to make sure to have an evacuation siren system. There is a regular check of these evacuation systems as well as mock drills to prepare the employees to react to an actual emergency.
Some vendors deal in the selling and installation of the evacuation siren system, and they also provide complete maintenance and repair options for these systems to the companies.