Forced air systems send heated air through duct-work. During warm weather the same duct-work can be reused for air conditioning. The forced air can also be filtered or put through air cleaners. Most ducts cannot fit a human being (as they do in many films) since this would require a greater duct-structural integrity and create a potential security liability.

Heating can also be provided from electric, or resistance heating using a filament that glows hot when you cause electricity to pass through it. This type of heat can be found in electric baseboard heaters, portable electric heaters, and as backup or supplemental heating for heat pump (or reverse heating) system.

The heating elements (radiators or vents) should be located in the coldest part of the room and typically next to the windows to minimize condensation. Popular retail devices that direct vents away from windows to prevent "wasted" heat defeat this design parameter. Drafts contribute more to the subjective feeling of coldness than actual room temperature. Therefore, rather than improving the heating of a room/building, it is often more important to control the air leaks.