A unit of measure of noise used most commonly in reference to exhaust fans.  A “low sone fan” means that it is quiet.

A unit of measure of air pressure used most commonly in reference to HVAC systems design.  

Air supply registers are located throughout a building to allow air to enter the conditioned space after it has been heated or cooled by the furnace / air conditioning unit. Registers usually have a damper to adjust the volume of the airflow. Some registers also have adjustable vanes so airflow can be adjusted to cover the [...]

A vent in a home that lets air return to the furnace where the air is heated or cooled and delivered back into the living spaces through ductwork and supply registers. Return air grilles usually do not have a damper. They can be located in each room, or sometimes in smaller homes there will be just [...]

An enclosure in which air pressure is greater or less than outside the enclosure; most commonly refers to the space above a suspended ceiling in a commercial building when it is used as the return air for the HVAC system – a “plenum ceiling”; also used to refer to the main supply and return air ducts [...]

Air operated; pneumatic controls are commonly used in commercial HVAC systems. 

When more air is being mechanically exhausted from a building than can be “made up” through openable windows, vents or make-up air HVAC equipment, the interior space has lower pressure than outdoor air. When air rushes in through exterior doors when they are open the space is under negative pressure. Also: Make-up Air Unit

A term describing air that is let into a building to “make up” for air that is being exhausted from the building. When a building space requires large amounts of exhaust ventilation, the HVAC system for the space must be sized to bring in outdoor air and condition, heating or cooling it and then delivers it [...]

See Hot Water Heating System