On occasion in our industry, certain types of tanks explode or catch fire, sometimes, but not always, during electrical storms. These tanks include SWD, produced water, frac tanks and distillate tanks. The problem occurs with steel, lined-steel and fiberglass tanks. The two possible causes of these incidents point to static discharge and/or lightning. Lightning may be the cause of some incidents, but it is not the likely culprit in most cases. It is unlikely that lightning attachment caused burn-through or heating ignition of vapor in these tanks. Therefore, the most likely cause is static discharge. The source of static may be the result of normal operations such as filling or draining, or it may be secondary effect from a direct or nearby lightning strike. Secondary effect arcing is also static discharge, albeit high energy and occurring over a short time frame. This arcing is produced by the inrush of ambient ground charge toward the point of a lightning strike. The inrushing charge can arc across gaps in its path, thus providing both a static charge and a static discharge. Therefore, the ideal protection system would address both causes.