21 00 00 - Fire Suppression
22 00 00 - Plumbing
23 00 00 - Heating, Ventilating, and Air Conditioning (HVAC)
23 09 00 - Instrumentation and Control for HVAC
23 50 00 - Central Heating Equipment
23 60 00 - Central Cooling Equipment
23 70 00 - Central HVAC Equipment
23 80 00 - Decentralized HVAC Equipment
40 90 00 - Primary Control Devices
40 91 00 - Primary Control Valves