**HVAC = Heating, Ventilation, Air Conditioning**

Think of the word conditioning the way a sports trainer conditions an athlete.

Your home bedroom has one split AC. Works perfectly for that one room.

The AHU serves an entire floor from one central location. But individual rooms — a hotel bedroom, a hospital patient room, a private office cabin — need individual temperature control.

A bus runs from one end of a city to the other. At some stops — many passengers get on. At others — few. The bus still runs the same route at the same speed regardless. That is inefficient.

The AHU cools air using chilled water coil. The FCU cools room air using chilled water. But where does all this chilled water come from?

Your kitchen at home. When cooking on a gas stove — LPG burns and produces combustion gases. Heat and steam fill the kitchen. In 10 minutes without ventilation — filled with smoke and fumes.

Basement car park. 6PM. Peak exit time. Twenty cars start engines. Reverse. Drive toward ramp. Each releasing exhaust gases.