Air Supply Unit

Because of the toxic smoke in a burning building, firefighters wear breathing air packs called self contained breathing apparatus (SCBA), similar to divers' SCUBA tanks. The SCBA air packs are also used at hazardous material incidents to protect them from hazardous atmospheres. Unfortunately, the standard tanks are only capable of carrying 30 minutes of air, this time is drastically reduced during strenuous work. All fire department engine and ladder companies carry spare bottles, but in multiple alarm fires or hazardous material incidents the air in the tanks and spare bottles are used up quickly. A supplemental supply of breathing air is needed at these large incidents, which is the role of the Air Supply Unit. 
     
     The Waltham Auxiliary Fire Department Air Supply Unit (ASU). carries a cascade system of twenty four high pressure breathing air cylinders. The unit is capable of refilling 300+ firefighters air tanks. Because of smoke and contaminants in the air at a fire scene, breathing air cannot be drawn into the cascade system at an incident, requiring the truck to bring the air to the scene. The truck's air tanks are filled by a high pressure breathing air compressor located at the Auxiliary station. When emptied, refilling the ASU bottles can take up to 24 hours. 
The Air Supply Unit also carries a 15kw electric generator that provides lighting for the air supply operations or to supplement the lighting capability of the Lighting Plant. The lighting capability includes four 1,500 wt telescoping flood lights, numerous hand lights and cable.

     In 1999, the department replaced the former ASU an, International utility, which as served the department well for the last five years with a 1975 Maxim, which was the former Wilmington Fire Department Engine 1. The new truck increases the air capacity by one third and substantially increases the equipment carrying capacity. The new truck also can carry a crew of four, doubling the crew size.

     The truck carries 24 - 444 cubic feet (cf.) of 4,500 pounds per square inch (psi) air cylinders. An electric booster pump expands the capability of the system by boosting tank pressure from as low as 120 psi up to 4,500 psi. The unit is capable or refilling over 200 of the 4.5, high-pressure self contained breathing apparatus (SCBA) bottles or over 300 of the 2.2 SCBA bottles.

     This unit has the highest capacity of any fire department air supply unit in Massachusetts. Most fire departments have a truck that carries spare bottles to the emergency scene. The Waltham ASU has the capability to refill the firefighters air packs at the scene of the emergency. Underwater rescue diver's SCUBA tabs can also be refilled by this system.