What is a unit heater designed to do?

A unit heater is specifically designed to deliver warm air directly into a space, effectively heating that environment. These heaters work by taking in cooler air from the surrounding area, heating it using a heat exchanger or electric heating elements, and then circulating the warmed air back into the room. This process creates a comfortable and controlled indoor temperature, making unit heaters particularly effective in situations where quick and localized heating is desired.

The other options represent different functionalities. For instance, delivering cold air would be a function of an air conditioning unit rather than a heater. Heating water is typically the role of a water heater or boiler, not a unit heater. Providing ventilation pertains to ensuring adequate air quality and circulation in a closed room, which is generally managed by ventilation systems or fans, rather than by unit heaters designed solely for heating. Thus, the correct answer highlights the primary role of a unit heater in space heating.