While records from 2005 indicate that less than one percent of Marietta Fire responses accounted for hazardous conditions, firefighters often encounter hidden dangers when they respond to other types of calls. Many people store or transport substances that can complicate what might ordinarily be a simple fire or medical response. Vehicle accidents, for example, are notorious for creating hazards such as fuel spills, propane leaks from RV's and disrupted substances that a driver might be transporting. While the danger of a fuel spill from a passenger car may be relatively small, consider the danger when a dump truck overturns and his truck's two 50-gallon saddle fuel tanks rupture.
When the magnitude of an incident exceeds the capability of a single department, a regional or larger response may be needed. Some substances expand as they change from a liquid to a gas, while others may react violently with water. If the first fire unit on a scene does not know that an underlying condition exists, a situation can rapidly mushroom beyond that unit's capability. In that case, the unit's officer would call for the hazardous materials team. Most of these highly trained individuals operate at the technician level, but there is a more elite group whose members have gone on to complete training on the specialist level.
Firefighters participate in a drill held at Southern Ice Cream. Marietta Fire personnel completed a combined total of 2,600 hours of hazardous materials operations level training in 2005.
Small signs known as placards identify significant amounts of materials that are being transported. This trailer's placards indicate that the driver is transporting both corrosive and radioactive materials.
American interstates and railroads carry varying amounts and forms of hazardous chemicals. The firefighters who responded to this motor vehicle accident on Interstate 75 found a tractor trailer carrying a large container of trichloroisocyanuric acid.