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 was shut off; electricity to portions of the three communities was also interrupted to avoid igniting any lingering gas. Thousands of people were told to shut off their gas service and evacuate their homes. In Lawrence, Mayor Dan Rivera urged residents in the city to move north of the Merrimack River. Schools and senior citizen centers were opened up in all three areas to take in the evacuees, and hotels offered shelter as well. The number of people evacuating by vehicle soon caused gridlock on streets that were already experiencing congestion by the afternoon rush hour commute. Merrimack College evacuated