This is the evaporator coil of the air conditioning system and heating unit for the house.
Heating systems are a major cause of home fires.
A good maintenance program and proper use can lower the chance of fire. The system should be checked and maintained by a qualified person twice a year. A recessed concrete floor with a floor drain is one way of reducing the amount of water damage from a leaking washing machine or air conditioner. The floor recess helps contain the spill by preventing water from spreading along the floor and under walls. In this house, the recessed slab extends under the air conditioner and washing machine.