The temperature scale on which water freezes at 32 degrees and boils at 212 degrees; designated by the letter F. To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit number, multiply by 5 and divide by 9 (77 -32 equals 45, times 5 equals 225, divided by 9 equals 25 degrees Celsius).

A shortened term for "air filter". Refer to "air filter" for HVAC specifics. Otherwise, a general term used to describe the removal of particles from a gas or liquid by straining.

A type of air duct material, often continuous, that is easy to route around obstacles in attics, etc, by bending it gently. Also referred to as Flex.

A pipe that vents combustion gases to the outside air, usually through convection.

A term to describe a system for heating, air conditioning, ventilation (or a combination of these) that uses a fan or blower to move or "force" air through the system and into the intended rooms.

A general term used to identify, any of a group of partially or completely halogenated simple hydrocarbons containing fluorine, chlorine or bromine, which are used as refrigerants.

The part of an HVAC system which converts gas, oil, electricity or other fuel into heat for distribution within a home or structure.