~ National Lightning Safety Institute ~
Overview of Lightning Detection Equipment
By Richard Kithil, President & CEO, NLSI
Lightning hazards can be mitigated by advanced planning. One part of this safety program should include an early detection and warning alarm package. Lightning detectors can give notice to shut down dangerous operations before the arrival of lightning. (Note there is no defense from a "first strike" situation.) Detectors also may signal "all clear" conditions after the lightning threat has passed. Some type of detection package may help you with issues involving duty-to-warn, liability, or negligence issues.
Lightning detectors vary in complexity and cost from large dedicated equipment packages costing in excess of $150,000 to inexpensive $20 to $30 Radio-Shack-type portable AM-FM weather radios. Network systems consisting of off-site information services are available in many places. A very good detector already exists in all our brains: Hearing thunder indicates the accompanying lightning is within your hearing range. (Thunder and lightning always happen together — acoustic and electrical signatures.) You see lightning but don’t hear thunder? That particular lightning was beyond your hearing range.
The distances from lightning Strike A to Strike B to Strike C easily can exceed more than 6-8 miles. Hear thunder? How much time is needed to get to shelter? Two to four minutes is suggested. Suspension of activities is very site-specific. For general situations, we recommend activating your lightning defense when thunder is first heard. Immediately find shelter! We also recommend waiting to resume activities 30 minutes after the last observed lightning or thunder, even though this protocol may seem excessively conservative in many situations ("we'll never get anything done under such strict guidelines"). It is a case-by-case risk management decision. And yes, safety and productivity sometimes are incompatible. Safety, however, always should be the prevailing directive.
We suggest three-stage warning criteria consistent with the recommendations contained in NFPA 780:
Available technologies of present-day lightning detectors include:
Beware of a false sense of confidence from detectors; none of them will detect all of the lightning all of the time. None of them will provide "first strike/bolt-out-of-the-blue" information or forecast in advance the positions of lightning strikes on earth. Beware especially of hand-held detectors' reliability. Vendors who claim to "predict" lightning in advance (which is impossible; it's just guesswork) should be rejected.
Detectors can display early warning of lightning conditions to hazardous operations. Some detectors can be relayed to start/stop standby power generators. A signaling or alarm notification method is essential to alert field personnel of developing dangerous circumstances. Two-way radios, remote-activation siren packages, strobe lights, and other methods are available.
Essential companions to any type of lightning detector include:
For many situations, if you hear thunder, your (brain) detector is working fine. Since lightning and thunder always occur paired, the lightning associated with the thunder you just heard is within your hearing distance — some 6 to 8 miles. Immediately go to safe shelter. No place outside is safe!
Select the detector and/or signaling device that is site-specific to your requirements, easiest to use, and offers the most favorable cost/benefit to your operation's budget. No detector is 100% perfect.
Summary: Detectors give advanced notice of the lightning hazard. Now resolve related issues to mitigate the hazard: Where is safe refuge? How long will it take to get there? How long should you stay there? Is it comfortable to stay there? What about protection for computers, servers, and telecommunications equipment? Are facility bonding and grounding and surge protection OK? Are defenses for process control operations installed? Is overall electric power continuity assured? Are outdoor workers educated and trained adequately?
Need help? Contact NLSI for assistance.