What type of systems is required for each interior space intended for human occupancy?

In the context of the International Mechanical Code (IMC), a heating system is essential for each interior space intended for human occupancy to ensure a comfortable and safe environment. This requirement is based on the need to maintain appropriate indoor temperatures, particularly in regions subject to cold weather. A heating system helps to prevent hypothermia and contributes to a conducive atmosphere for occupants to perform daily activities comfortably.

While ventilation systems are also important for maintaining air quality and removing excess moisture, and cooling systems are crucial in hot climates, the primary focus of this question revolves around the necessity of heating systems. Congregation systems are not a recognized category within the IMC and do not pertain specifically to maintaining the environmental comfort of occupied spaces.

In summary, a heating system is vital for human comfort and safety in occupied spaces, making it the correct answer.