What is a heating system primarily used for?

A heating system is primarily designed to maintain indoor temperature, providing a comfortable and controlled environment within a building. It achieves this by generating heat and distributing it throughout the spaces occupied by people. This can involve various types of systems, such as radiators, underfloor heating, or centralized heating units that use various fuel sources like gas, oil, or electricity.

When it comes to the other options, while they may be relevant to building services, they do not directly pertain to the primary function of a heating system. For instance, providing a gas supply pertains to the delivery of fuel needed for heating, but it is not the function of the heating system itself. Distributing electrical power relates to electrical infrastructure, which is a separate element of building services. Similarly, ensuring air circulation is more associated with ventilation systems rather than heating; while both heating and ventilation are important components of indoor climate control, the primary focus of a heating system is specifically on temperature maintenance.