Mechanical systems include heating, ventilation, and air conditioning (HVAC) systems. They regulate indoor air quality, temperature, and humidity to create a comfortable environment for occupants. Mechanical systems also encompass equipment such as boilers, chillers, pumps, and fans. 

Electrical systems involve the distribution of electrical power throughout a building. This includes wiring, electrical panels, switches, outlets, and lighting fixtures. Electrical systems provide power for lighting, appliances, equipment, and other electrical devices, as well as support for communication and technology infrastructure. 

Plumbing systems encompass water supply, drainage, and sewage systems within a building. This includes pipes, fixtures, fittings, and valves for conveying potable water, removing wastewater, and managing sewage. Plumbing systems also include fixtures such as sinks, toilets, showers, and water heaters. 

Fire protection systems are designed to detect, suppress, and mitigate fires in buildings. This includes fire alarm systems, fire sprinkler systems, fire extinguishers, and smoke control systems. Fire protection systems help to ensure the safety of occupants and minimize property damage in the event of a fire.