Electrical equipment in hazardous areas the participation of operations, maintenance, safety, electrical and instrumentation professionals, the use of process diagrams and material flows, MSDS and any pertinent documents, information and knowledge to determine the hazards and their extent and the countermeasures to be employed. Area classification documentations are reviewed and updated to reflect process changes. Soon after the introduction of electric power into coal mines, it was discovered that lethal explosions could be initiated by electrical equipment such as lighting, signals, or motors. The hazard of fire damp or methane accumulation in mines was well known by the time electricity was introduced, along with the
Merrimack Valley gas explosions in the low-pressure pipes. At the time of the accident, workers were replacing some of the low-pressure piping, but the procedure set out by Columbia Gas for doing this failed to include transfer of a regulator's pressure sensor from the old, disused piping to the new. As a result, when the old pipe was depressurized, the regulator sensed zero pressure on the low-pressure side and opened completely, feeding the main pipeline's full pressure into the local distribution network. Within minutes, buildups of natural gas were causing explosions and fires in houses across Lawrence, Andover and North Andover. Multiple explosions and