Auxiliary mechanics The other major place to find Machinist's Mates is in the auxiliaries division of engineering department, often referred to as "A-gang". Mechanics in this role establish training & work on mechanical equipment within and outside of the engine rooms. To include the operation and preventive maintenance of: air conditioning and refrigeration units, liquid oxygen and nitrogen units, hydraulic lifting and hoisting gear, hydraulic power plant components and mechanisms, chilled and fresh water, atmosphere control, ventilation, emergency diesel and corresponding sub-systems, ballast control, auxiliary drain, compressed air and gases, plumbing, trash disposal & other equipment as designated by the Engineering Officer (Chief Engineer, or CHENG). Members of "A-gang" may also help Damage Controlman, Gunner's Mates, or other ratings. Some listed attributes apply to Submarine Warfare to include SUBSAFE requirements for work authorization. All systems listed apply to a minimum of valve, pump maintenance repair. "A-gang" rates can be submarine qualified and will go through BESS (Basic Enlisted Submarine School) and then proceed forward to their A-school training specific to Machinist Mate rate where they will learn the above-mentioned skills. This schooling takes place in Groton, Connecticut. Nuclear mechanics Some MMs are qualified to work on nuclear propulsion plants. They are designated as Machinist's Mate nuclear (MMN). These mechanics go through a rigorous training program consisting of three months at the Nuclear Field "A" School or in previous years Machinist's Mate "A" School, six months of Naval Nuclear Power Training Command also known as Nuclear Power School, and six months at one of several Nuclear Power Training Units (NPTU). Two NPTUs are moored training ships (MTS) using S5W reactors located at the Naval Weapons Station in Charleston, South Carolina, and two additional NPTUs are land-based prototype units using a modified S5W reactor (MARF DMC) and an S8G reactor located in Ballston Spa, New York. NPTU Idaho (now decommissioned) at the Naval Reactors Facility operated the first prototype from 1953 to the mid-1990s which was for the , named S1W, the prototype for the , named A1W, and S5G, which are all shutdown and defueled. This course of instruction is commonly referred to as "the nuclear-power pipeline". MMNs earn a N25O NEC (surface) or N15O (submarines) upon completion of prototype. Along with the normal duties of a propulsion mechanic, they are responsible for the operation, maintenance, and repair of the auxiliary equipment in support of the Naval reactor(s) under their care.