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In 2019 we installed the most modern siren system in the areas of the Self-Rescue Zone*, with a sound intensity of 70 dB, at all units in Brazil, in the metallurgy and mining sectors. Our mass evacuation system has not only sound alerts but also voice resources (both pre-recorded and live-voice), which offers greater efficiency and eliminates any possibility of confusion, thus minimizing panic, restoring order, and bringing safety to the local populace. We use OMNI-360º sirens, specifically designed for open areas and with completely autonomous operation, powered by a photovoltaic system (solar energy).
Regardless of the wind direction, the sound continues to be propagated in all directions within the area of interest. The sound design includes sirens with 360° propagation, and the system’s robust performance has been proven throughout the last 35 years, with more than 20,000 sirens installed in 50 countries around the world. The system is STI-certified (SPEECH INTELLIGIBILITY INDEX) and meets the International Standard ISO 9921-2003 (ERGONOMICS – ASSESSMENT OF SPEECH COMMUNICATION), which is one of the world’s best known standards regarding clarity of voice emission. Our system is called SI TEST® which is activated automatically once a day, without disturbing the communities in the protected areas. In this test, each amplifier, speaker driver, battery charger, battery bank, and radio signal are checked individually, being indicated by an alarm registered in the Control Center. Additionally, an audible test is performed daily, as a second test to verify system operation. The sirens are in accordance with the requirements of the latest Brazilian legislation, which provides for a range within a radius of 10 kilometers or a flood wave equal to 30 minutes. We are currently in the process of automating the geotechnical instrument monitoring process. In addition to the online monitoring required by law, we conduct onsite inspections every 15 days.


The siren implemented by Nexa is the same one used in the USA for hurricane notification.

* The delimitation of the Self-Rescue Zone* is prepared according to the determination of DNPM Ordinance 70389 of May 17, 2017:

“Valley region downstream from the dam where the warning notices to the populace are considered as being the responsibility of the enterprise, since there is not enough time for the competent authorities to intervene in emergencies. The following distances must be adopted for its delimitation, whichever is greater: the distance corresponding to a flood wave arrival time equal to thirty minutes, or ten kilometers.”