Outlined below are the most commonly used hvac ductwork symbols and their meanings.
Click here to view easy-to-use compiled charts of these symbols.
Straight duct
Ducts are conduits or passages used in hvac systems to move air.
branch duct
In order to split air passage among spaces, branch ducts are used.
duct bend
In order to make smooth turns and avoid turbulence bend pieces are used in the air passage.
y-junction
3-way junction
junction
beveled junction
Such junctions are used when a part of the air from the main passage is diverted to a certain space.
miter bend
A miter bend(elbow) is made by mitering or bevel cutting two pipes or ducts usually to form a 90 degree turn.
Duct Transition
Used to reduce to effective diameter of a duct. Transitions are required to change the overall size or shape of a duct.
Duct offset Transition
Supply Ceiling Diffuser
Distributes conditioned air uniformly throughout the room. These are visible on the ceiling.
Return Ceiling Diffuser
Collects return air from the room. These are visible on the ceiling.
Flexible Connector
Flexible connectors are used as attachments between ducts and equipment in order to reduce noise and vibration.
VAV Box
Variable Air Volume(VAV) boxes maintain the temperature of a space by controlling the supply of conditioned air through the duct into the space.
Duct Damper
Duct dampers are control devices in ducts that function like butterfly valves to control airflow.
Linear Diffuser Supply/Return
Linear diffusers distribute air evenly throughout a space.
Floor Register
A register is a grille with air flow adjustment.
Air grilles
Air grilles are used to evenly distribute air in a space.
Duct Heater
Used to heat air flowing through a duct.
Flexible Connection
Used to reduce noise and vibration.
Louver Opening
Louver is a device used in hvac ventilation systems to allow air to pass through while keeping out dirt and debris.
New Ductwork
INSULATED DUCTWORK
Insulated ducts are used to reduce thermal energy loss and prevent condensation on ducts.
EXTERNALLY INSULATED DUCTWORK
Insulated ducts are used to reduce thermal energy loss and prevent condensation on ducts.
FIRE RATED DUCT SYMBOL
Fire resistant ducts help maintain compartmentalization and divert smoke.
volume control damper
Used to control volume of air passing through a duct.
fire damper
Fire dampers are fire protection devices used to prevent spread of fire through ducts.
flexible connection
duct spigot with butterfly damper
non return damper
Non return dampers ensure airflow in single direction
duct mounted attenuator
Used near AHUs/FAHUs to reduce transmission of noise.
Motorised damper/ motorised smoke & fire damper
Performs the same function as a regular damper but is motorised and can be controlled automatically.
circular flexible duct
DUCT RISER
Duct that rises vertically through a building or structure.
DUCT DROPPER
Duct that drops vertically through a building or structure.
duct acoustic lining
Duct acoustic liners are primarily used for sound absorption.
vertical duct section
circular diffuser
supply duct section
return duct section symbol