This is a follow-up to an earlier blog (see: "Emergency Response Exercise – Hamilton County, TN") about an evaluation of a local Reverse 911 System during a chemical response drill. A recent article on TimesFreePress.com reported on the results from the exercise. During the exercise 500 people living within 1.5 miles of the training center were called by the Reverse 911 system and notified that a training exercise was taking place.
Reverse 911 System Evaluation
The Reverse 911 system contacted someone in just a little over 1/3 of the calls made (177). About 20% (102) of the calls reached answering machines. What is not known is how many of those messages left on answering machines would have reached real people in a timely manner. Less than 100 of the numbers dialed resulted in busy signals or no answer. More than 20% of the calls (109) resulted in ‘network errors’. No explanation was given for the probable causes of those errors.
Unfortunately nothing in the report allows county emergency personnel to evaluate how effective the Reverse 911 System was at notifying people in the area. To do this there would have had to be a door-to-door canvas of the neighborhood to find out how many people had been present and how many had been notified via the system. This would be a valuable piece of data to have.
Lessons Learned
The local fire chief was quoted in the newspaper article as saying "It’s important that (Reverse 911) works because it’s the best way to ... get the message out to evacuate and get to safety,"
I’m not sure that the 1/3 contact rate seen in this exercise would be considered an adequate notification rate for an evacuation. The next best alternative is to go door to door to make notification, a manpower intensive exercise at best. Considering that the people going door to door are facing potential exposure to the chemical of concern and the safety of that system is suspect. Emergency sirens or alarms could be used, but they are able to transmit only limited information.
Hamilton County, TN is looking into adding cell phone numbers to their Reverse 911 System, according to a fire department spokesman. This makes some sense if the number used can be targeted for a specific area. The FCC is working on a system that would allow an emergency message to be targeted to all cell phones in a given area (based on cell tower locations).
Considerations for Emergency Response Messages
In a toxic chemical release emergency there are going to be four potential responses for people in the area around the release. The worst case is that people in the highest concentrations of the toxic cloud will need to don protective clothing (perhaps just a respirator). The next nearest area of exposure will need to shelter-in-place. People a little further away from the incident will be able to safely evacuate before toxic levels of the chemical reach them. The final group of people will need to take no special precautions due to how far they are removed from the incident.
An emergency notification system must be able to take into account the different response required for different locations. Giving sound advice to the wrong people makes that advice ineffective at best. At worst that advice could be deadly.
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