Learn what the crew means.

Air Drop

Vertical drop of air stream.

Anti-smudge ring

Ring to prevent ceiling.

CFM

Airflow volume measurement.

Core diffuser

Diffuser with removable center section.

Core removal

Diffuser core can be removed.

Core velocity

Velocity at diffuser inlet.

Damper box

Box with integral damper for register.

Diffuser

Air outlet with engineered airflow pattern.

Diffuser boot

Transition from duct to diffuser.

Eggcrate grille

Grille with eggcrate pattern.

Exhaust grille

Grille for exhaust air.

Face size

Visible face dimension of diffuser.

Face velocity

Velocity at diffuser face.

Grille

Fixed blade air outlet/inlet.

Linear diffuser

Long narrow diffuser.

Louvered face diffuser

Diffuser with adjustable louvers.

Neck size

Duct connection size of diffuser.

Noise criteria

Sound level rating of diffuser.

Opposed blade damper box

Perforated diffuser

Diffuser with perforated face.

Perforated face

Face with holes for airflow.

Plenum slot diffuser

Diffuser for T-bar ceiling plenum.

Pressure drop

Pressure loss through diffuser.

Register

Grille with integral damper.

Return air grille

Grille for return air intake.

Return diffuser

Diffuser for return air.

Single blade damper box

Spread

Lateral spread of air from diffuser.

Step-down diffuser

Diffuser with stepped face.

Supply diffuser

Diffuser for supply air.

Surface mount diffuser

Mounts on surface of ceiling/wall.

T-bar diffuser

Diffuser for T-bar ceiling grid.

Terminal velocity

Velocity at end of throw.

Throw

Distance air travels from diffuser.

Transfer grille

Grille in partition for air transfer.

Access door

Removable panel for inspection/cleaning.

Automatic balancing damper

Self-adjusts to maintain set airflow.

Auxiliary switch

Additional position indication switch.

Balancing damper

Manually adjusted for airflow balance.

Barometric relief damper

Opens at set static pressure.

Blade linkage

Connects blades to actuator.

Breakaway connection

Connection that fails at high temperature.

Ceiling penetration

Duct through rated ceiling.

Ceiling radiation damper

Protects ceiling membrane penetrations.

Combination fire/smoke damper

Combined fire and smoke protection.

Control wiring

Wiring for electric damper controls.

Corridor damper

Smoke damper in corridor duct.

Curtain blade damper

Blades fold like curtain when closing.

Damper access panel

Panel for damper inspection access.

Damper actuator

Device that opens/closes damper.

Damper blade

Moving part that closes damper.

Damper blade seal

Seal on damper blade edges.

Damper commissioning

Final verification of damper function.

Damper frame

Outer frame containing damper.

Damper frame seal

Seal around damper frame.

Damper heater

Prevents damper freezing.

Damper jack

Temporary hold-open during installation.

Damper operator

Device that operates damper.

Damper position switch

Indicates damper position.

Damper schedule

List of all dampers on project.

Damper sleeve

Duct section housing damper.

Damper sleeve gauge

Thickness of damper sleeve material.

Damper tag

Identifies damper location and rating.

Damper testing

Verifying damper operation.

Dynamic closure

Damper closes against airflow.

Electric actuator

Electrically powered damper operator.

End switch

Indicates damper fully open/closed.

Fire damper

Closes when temperature exceeds rating.

Fire damper inspection

Testing fire damper operation.

Fire damper installation

Process of installing fire damper.

Fire rating

Duration of fire resistance (e.g., 1.5 hr, 3 hr).

Fire/smoke wall penetration

Duct through fire-rated wall.

Firestat

Temperature-activated fire safety device.

Firestop

Seals penetration for fire rating.

Firestop pillow

Compressible firestop material.

Firestop putty

Moldable firestop material.

Floor penetration

Duct through fire-rated floor.

Fusible link

Melts at set temperature to close damper.

Fusible link rating

Temperature at which link melts (e.g., 165°F, 212°F).

Gravity vent damper

Opens by gravity, closes by spring.

Heat detector

Detects excessive heat.

Jackshaft

Shaft connecting multiple damper sections.

Modulating actuator

Positions damper at variable openings.

Motorized control damper

Electrically controlled damper.

Motorized fire damper

Fire damper with motorized closure.

Multi-blade damper

Multiple blades in parallel or opposed arrangement.

Parallel blade damper

Blades rotate same direction.

Pneumatic actuator

Air-powered damper operator.

Pneumatic tubing

Tubing for pneumatic controls.

Resettable fusible link

Fusible link that can be replaced.

Shaft bushing

Bearing for damper blade shaft.

Sleeve length

Required length of damper sleeve.

Smoke damper

Closes to prevent smoke spread.

Smoke damper inspection

Testing smoke damper operation.

Smoke damper installation

Process of installing smoke damper.

Smoke detector

Detects smoke in ductwork.

Smoke detector sampling tube

Tube extending into duct for sampling.

Spring return actuator

Returns to default position on power loss.

Stairwell pressurization damper

Maintains stairwell pressure.

Static closure

Damper closes with no airflow.

Two-position actuator

Only fully open or fully closed.

UL 555

Standard for fire dampers.

UL 555S

Standard for smoke dampers.

Volume control damper

Adjusts airflow volume.

Acoustic sealant

Remains flexible for sound sealing.

Beam attachment

General beam hanger attachment.

Beam clamp

Clamps to steel beam for hanger.

Brazed joint

High-temperature solder joint.

Button punch joint

Mechanically locked joint.

Butyl sealant

Rubber-based sealant.

Canvas connector

Canvas sleeve for equipment connection.

Closed-cell gasket

Compressible gasket material.

Closed-end rivet

Sealed mandrel end.

Companion angle joint

Bolted angle iron flange connection.

Concrete insert

Embedded concrete hanger point.

Concrete screw

Screw for concrete attachment.

Corner piece

Corner reinforcement for duct.

Crimp and slip joint

Crimped end slips into next section.

Cross break joint

Joint with cross-break stiffening.

Draw band joint

Sealed with draw band.

Drive cleat joint

Uses drive cleat with S-cleat.

Drop-in anchor

Threaded insert for concrete.

Duct connector

General connector piece.

Duct gasket

Rubber seal for duct joints.

Duct joint sealer

Putty-like sealant for joints.

Duct sealer

General term for duct sealant.

Duct tape

Tapes seams and joints.

Ductmate

Flagged: variation.

E-Z Flange

Flagged: manufacturer-specific.

Firestop caulk

Fire-rated sealant.

Flange bolt

Bolts for flange connections.

Flange gasket

Seals between flanged joints.

Flange nut

Nuts for flange bolts.

Flange sealant

Sealant for flange faces.

Flange washer

Washers for flange connections.

Flanged connection

Bolted flange connection.

Flexible connector

Flexible connection for vibration.

Gasketed joint

Joint with rubber gasket seal.

Intumescent sealant

Expands when heated to seal gaps.

Joint clamp

Clamps joint during sealing.

Joint reinforcement

Added material to strengthen joint.

Lag screw

Screw for wood attachment.

Large flange rivet

Rivet with large head.

Latex caulk

Water-based caulk.

Leak lock

Seals threaded connections.

Machine screw

Screw for threaded holes.

Mastic

Paste sealant for duct joints.

Multi-grip rivet

Works in range of thicknesses.

Neoprene connector

Rubber flexible connection.

Open-cell gasket

Soft gasket material.

Pittsburgh joint

Longitudinal seam joint.

Pittsburgh seam connection

Uses Pittsburgh lock for joint.

Polyurethane sealant

Durable flexible sealant.

Pop rivet

Fastener for metal connections.

Post-installed anchor

Anchor installed after concrete pour.

Pressure-sensitive tape

Tape with pressure-activated adhesive.

Raw edge joint

Simple overlapping joint.

Reinforcing tape

Tape with embedded mesh for strength.

Rod coupling

Connects threaded rod sections.

Rod hanger

Attaches rod to structure.

S-cleat joint

Uses flat S-cleat for transverse joint.

Seam weld

Continuous weld along seam.

Self-piercing screw

Drills own hole in sheet metal.

Sheet metal screw

General sheet metal fastener.

Silicone sealant

Flexible sealant for joints.

Sleeve anchor

Sleeve expands when bolt tightened.

Slip and drive connection

Common rectangular duct joint method.

Slip connection

Sliding fit connection.

Snap-lock joint

Interlocking round pipe joint.

Soldered joint

Joined with solder (rare in HVAC).

Solvent-based mastic

Stronger but more hazardous sealant.

Spot weld

Localized weld points.

Standing S joint

Uses standing S-cleat for transverse joint.

Standing seam connection

Uses standing seam for joint.

TDC

-. Verify the matching shop system, corners, gasket, and approved hardware before assembly.

Teflon tape

Seals threaded pipe joints.

Tek screw

Self-drilling fastener with drill point.

Threaded rod

Continuously threaded rod for hangers.

Toggle bolt

Anchor for hollow walls.

Transverse duct connector

Roll-formed flange connection system.

Transverse duct flange

Four-bolt flange system, distinct from TDC.

UL 181 mastic

UL-listed duct sealant.

UL 181 tape

UL-listed pressure-sensitive tape.

Vapor barrier tape

Seals insulation vapor barrier.

Water-based duct mastic

Common water-based sealant.

Wedge anchor

Expands in concrete hole.

Welded connection

Permanent welded joint.

Open →Trade word · Materials

Zip screw

Pierces thin sheet metal.

G90

Galvanized coating.

Backdraft damper

Allows flow in one direction only. Prevents reverse airflow.

Barometric damper

Opens at set pressure to relieve excess.

Blade seal

Seal on damper blade edges.

Boot

Transition from duct to register/grille.

Bottom tap

Branch outlet from bottom of duct.

Branch line

Duct branching from trunk.

Conical tap

Tap with conical transition to round.

Converging section

Narrowing transition section.

Cross

Four-way intersection fitting.

Damper jackshaft

Shaft connecting multiple damper sections.

Damper linkage

Connects actuator to damper blades.

Damper quadrant

Handle for adjusting volume damper.

Diverging section

Widening transition section.

Double-wall vane

Vane with airfoil cross-section.

Duct collar

Rim for connecting duct to equipment or fittings.

Duct gauge

Thickness of sheet metal (e.g., 26 ga, 24 ga).

Duct leakage

Amount of air escaping duct.

Duct pressure class

Rated pressure (e.g., 2-inch wg, 4-inch wg).

Duct reinforcement

Added material to prevent duct deformation.

Duct section

Single piece of duct between joints.

Duct sleeve

Duct through wall/floor penetration.

Elbow

Direction change fitting.

End cap

Closes end of duct run.

Fire-rated sleeve

Sleeve with fire rating.

Flange

Rim for bolting duct sections together.

Frame seal

Seal around damper frame.

Header

Main distribution chamber.

HETO

Flagged: manufacturer-specific.

Hinged access door

Access door with hinges.

Leakage test

Testing duct for air leaks.

Motorized damper

Damper with electric/pneumatic actuator.

Offset

Fitting to avoid obstruction.

Opposed blade damper

Blades rotate in opposite directions. Blades rotate opposite directions.

Plenum

Large chamber for air distribution.

Radius elbow

Elbow with curved throat and heel.

Rectangular duct

Primary duct shape in commercial HVAC.

Riser

Vertical duct running between floors.

Saddle tap

Fitting welded/attached to side of duct for branch.

Seal class

SMACNA seal class (A, B, C).

Shoe tap

Tap with angled entry like a shoe.

Side tap

Branch outlet from side of duct.

Single blade damper

Single round blade in rectangular frame. Single round or rectangular blade.

Single-wall vane

Simple curved turning vane.

SMACNA standards

Sheet Metal and Air Conditioning Contractors' National Association standards.

Smoke damper sleeve

Sleeve housing smoke damper.

Splitter damper

Diverts airflow between branches.

Square elbow

90-degree elbow with mitered corners.

Stack head

Fitting at top of vertical riser.

Standing seam

Seam running length of duct.

Tee

90-degree branch fitting.

Top tap

Branch outlet from top of duct.

Transition

Changes duct size or shape.

Transverse joint

Joint between duct sections.

Trunk line

Main distribution duct.

Turning vanes

Curved blades in elbow to reduce turbulence.

Vane rail

Track that holds turning vanes.

Vane spacer

Maintains spacing between vanes.

Volume damper

Manual airflow adjustment damper.

Wye

Branching fitting with angled split.

Adjustable swivel ring

Ring with swivel for angled pipe.

Angle ring connector

Angle iron ring for bolting round duct.

Band saw

Power saw for straight cuts.

Bead crimp

Crimp with reinforcing bead.

Bell end

Flared end for pipe joint.

Clevis hanger

U-shaped hanger for round pipe.

Concentric reducer

Reducer centered on axis.

Crimp

Reduced end for fitting into next section.

Draw band

Metal band for sealing round duct joints.

Duct fabric connector

Fabric sleeve for equipment connection.

E-Z Tap

Flagged: manufacturer-specific.

Eccentric reducer

Reducer with offset centerlines.

Flexible duct connector

Flexible connection for vibration isolation.

Floor support

Freestanding support for pipe.

Flow straightener

Reduces turbulence for measurement.

Gored elbow

Elbow made from gore sections.

Lap joint

Overlapping pipe connection.

Longitudinal seam pipe

Round pipe with straight longitudinal seam.

Mitered Elbow

Sharp rectangular elbow without a smooth radius; turning vanes or another approved airflow treatment may be required by the design or specification.

Neck adaptor

Connects different sizes/types. Connects duct to diffuser neck.

Oval duct

Flattened round duct for low clearance.

Oval major axis

Long dimension of oval duct.

Oval minor axis

Short dimension of oval duct.

Ovalizer

Forms round pipe into oval shape.

Pipe clamp

Clamps round duct connections.

Pipe crimper

Crimpes end of round pipe.

Pipe cutter

Cuts round pipe cleanly.

Pipe diameter

Size specification for round duct.

Pipe gauge

Thickness of round duct material.

Pipe insulation sleeve

Pre-formed insulation for round pipe.

Pipe liner

Internal insulation lining.

Pipe notcher

Notches round pipe for saddle fit.

Pipe saddle support

Cradle support for round pipe.

Pipe shoe

Supports pipe while allowing movement.

Pipe stretcher

Expands pipe end for fitting.

Pipe support

Support for round duct.

Pipe wrap

Wrap-around insulation for pipe.

Pressed elbow

Factory-formed round elbow.

Reciprocating saw

Power saw for cutting pipe in place.

Riser clamp

Supports vertical round duct.

Round access cap

Removable cap for round duct access.

Round access door

Access opening in round duct.

Round backdraft damper

One-way damper for round duct.

Round cap

Closes end of round duct.

Round coupling

Connects two round duct sections.

Round elbow

Direction change for round duct.

Round fire damper

Fire-rated damper in round duct.

Round saddle

Branch saddle on round duct.

Round smoke damper

Smoke-rated damper in round duct.

Round tee

T-branch for round duct.

Round transition

Size change for round duct.

Round volume damper

Damper in round duct.

Round wye

Angled branch for round duct.

Snap-lock round pipe

Round pipe with snap-lock longitudinal seam.

Snap-lock seam

Interlocking seam for round pipe.

Spigot end

Plain end that fits into bell/socket.

Spin-in collar

Taps into round duct with cutting edge.

Spiral duct

Round duct with spiral lockseam.

Spiral lockseam

Continuous spiral seam on round duct.

Spiral pipe connector

Connects spiral pipe sections.

Spiral pipe machine

Forms spiral lockseam pipe from coil.

Split ring hanger

Ring that wraps around pipe.

Start collar

Collar for connecting to equipment.

Tab collar

Collar with tabs for securing to duct.

Takeoff collar

Collar for branch connection.

Test port

Small port for airflow measurement.

Vanstone flange

Flange that laps over pipe end.

Bead

Raised ridge for stiffening sheet metal.

Bend allowance

Material added for bend radius compensation.

Break metal

Sheet metal formed on a brake.

Burrs

Sharp edges left after cutting.

Cheek

Side panel of rectangular elbow.

Circumference rule

Tape measure showing diameter from circumference.

Cleat bender

Forms S-cleats and drive cleats.

Combination square

Multi-purpose measuring and layout tool.

Cookie

Scrap piece from cutting duct openings.

Cornermatic

Automated corner forming machine.

Cross break

X-shaped bends for panel stiffening.

Cut list

List of pieces to be fabricated.

Deburring

Removing sharp edges from cut metal.

Developed length

Flat pattern length before forming.

Drive cleat

Slip used with S-cleat for transverse joints.

Duct liner adhesive

Adhesive for attaching duct liner.

Elbow template

Pattern for laying out elbows.

Flat S-cleat

Horizontal S-shaped cleat for transverse joints.

Gauge

Sheet metal thickness.

Gore

Wedge-shaped section for forming round fittings.

Grain direction

Direction of metal grain from rolling process.

Heel

Outer curved section of elbow or transition.

Hem

Folded edge for safety and stiffness.

K-factor

Ratio for calculating bend allowance.

Layout dye

Blue fluid for marking layout lines.

Liner cap

Cap welded over liner pin.

Liner pin

Pin for securing duct liner.

Nesting

Arranging parts on sheet for minimal waste.

Pin welder

Welds pins for securing insulation/liner.

Pittsburgh Seam

Primary seam for rectangular duct longitudinal joints.

Prick punch

Makes small indentation for drill starting.

Raw edge

Unfinished edge of cut sheet metal.

Rotary lock former

Forms Pittsburgh locks on sheet edges.

Scriber

Sharp tool for marking metal.

Seam closer

Machine for closing Pittsburgh locks.

Sheet-Metal Drop

Leftover material from sheet.

Shop drawing

Detailed drawing for fabrication.

Spot welder

Welds overlapping sheet metal sections.

Standing S-cleat

Vertical S-shaped cleat for transverse joints.

TDC flange

Roll-formed flange system for rectangular duct. Verify the matching shop system, corners, gasket, and approved hardware before assembly.

TDF flange

Four-bolt flange system, distinct from TDC. Verify the matching shop system, corners, gasket, and approved hardware before assembly.

Throat

Inner curved section of elbow or transition.

Trammel points

For drawing large arcs and circles.

Wire edge

Edge rolled around wire for reinforcement.