A fire alarm is a system of classification used by fire departments and news agencies to indicate the level of response by local authorities. The most widely used formula for multi-alarm designation is based on the number of units and firefighters responding to a fire; the more vehicles and firefighters responding, the higher the alarm designation. A two-alarm fire call summons more trucks, with more firefighters, but more specifically, it calls for a hazardous materials vehicle and a support vehicle called a “supply shop.” These units provide additional equipment such as oxygen tanks. After a 2 alarm fire call goes out, there can potentially be up to 13 emergency vehicles on the scene of the fire. In Rochester, a two-alarm fire requires assistance from other departments for a couple more pumpers and ladder trucks. Some will go to the scene and the others will cover their stations.