Evacuation Terminology & Hi-Lo Sirens
In Douglas County, Colorado, the following terms will be used:
- Evacuation Order: Immediate threat to life. This is a lawful order to leave now. The area is lawfully closed to public access.
- Evacuation Warning: Potential threat to life and/or property. Those who require additional time to evacuate, and those with pets and livestock, should leave now.
- Shelter in Place: Go indoors. Shut and lock doors and windows. Prepare to self-sustain until further notice and/or until emergency personnel contact you for additional direction.
Why Hi-Lo Sirens?
Douglas County uses multiple emergency notification tools to reach its more than 400,000 residents, including opt-in systems like DougCoAlert and social media, as well as universal systems such as IPAWS (Integrated Public Alert and Warning System), Wireless Emergency Alerts (WEA), and the Emergency Alert System (EAS).
However, these systems rely heavily on cellular networks, radio signals, Wi-Fi connectivity, and commercial power. In mountainous terrain, areas with limited cell towers, during heavy smoke conditions, or when Public Safety Power Shutoffs (PSPS) occur, those systems may be delayed or fail entirely. Cell towers can become overloaded, lose power, or even be destroyed during fast-moving disasters.
Recent catastrophic wildfires — including the Palisades, Marshall, Lahaina, and Waldo fires — have demonstrated that under extreme conditions, evacuation needs can outpace digital notification systems. When that happens, real-time, field-based alerts become essential.
To address this vulnerability, the Douglas County Sheriff’s Office is installing Hi-Lo sirens and pre-recorded evacuation messages in patrol vehicles. The Hi-Lo system emits a distinctive alternating high-low tone followed by a clear recorded message:
“A MANDATORY EVACUATION ORDER HAS BEEN ISSUED FOR THIS AREA. PLEASE EVACUATE IMMEDIATELY.”
This critical warning system will only be used when incident commanders have issued an Evacuation Order during extreme emergencies and life-threatening events requiring immediate evacuation. This adds a critical layer of redundancy when traditional alerts, such as cell phone notifications, may fail due to power outages, damaged cell towers, or heavy smoke.
“This system is designed for worst-case scenarios — fast-moving wildfires, flash floods, major law enforcement incidents, or any critical event where lives are at immediate risk. Our adoption of the Hi-Lo siren and clear, standardized evacuation terminology ensures that when seconds matter, our residents will hear a distinct warning and know exactly what it means. It’s about clarity, speed, and giving our community every possible advantage in an emergency,” said Douglas County Sheriff Darren Weekly.