How to tag ducts in Revit: Tag by Category and Tag All Not Tagged, step by step

A duct tag is an annotation family that reads values from the duct. Size is the usual one. Many offices add the system, the elevation, or the airflow. Revit places the tag, and the tag family decides what it says.

This guide covers the whole job in order. You load a tag, place one by hand, tag a whole view at once, handle flex and angled ducts, change what the tag says, and then fix the problems people hit most. Each section works on its own, so jump to the one you need.

Under the steps, you will see where each one slows down on a real project, and what RayCAD does at that point. RayCAD is the Revit add-in we build for automated MEPF tagging.

What do you need before you tag ducts?

• A model with ducts in the view. Tags attach to the visible elements of the active view.
• A loaded tag for each category you plan to tag. Ducts, flex ducts, duct fittings, duct accessories, and air terminals each have their own tag category. A duct tag does not cover the others.
• Duct tags turned on in the view. Check the Annotation Categories tab in Visibility/Graphics (VG), and check that the view template does not hide them.

How do you tag a duct in Revit?

1. Load a duct tag family

Revit can only place a tag that is loaded in the project. If no tag is loaded for the category, Revit asks you to load one.

1. Go to the Annotate tab and open the drop-down arrow on the Tag panel.
2. Choose Loaded Tags and Symbols.
3. Click Load and browse to the tag. Hold Shift or Ctrl to select several files. The tags that ship with Revit sit in the Annotations folder of your Revit library, under Mechanical. The exact path depends on your Revit version and library setup.
4. Check that the tag name now appears next to its category, then click OK.

The last tag you load for a category becomes the default for that category. If your firm has its own duct tag, load that one last. Repeat the load for Flex Duct Tags and any other category you need.

2. Tag one duct with Tag by Category

1. Open the floor plan or the section view. Tags work in any view where the duct is visible.
2. Go to Annotate, Tag, Tag by Category, or type the shortcut TG.
3. Set the options in the next step.
4. Hover over a duct and click it. The tag appears.
5. Drag the tag, the leader, or the arrowhead to move it. The tag stays in edit mode right after you place it.
6. Press Esc twice to leave the command.

3. Set the orientation and the leader

In Revit 2026 these controls sit on the Properties palette and on the Modify | Tag tab. Older versions put them on the Options bar.

• Orientation. Horizontal, Vertical, or Model. After you place a tag, select it and press Spacebar to switch the orientation.
• Angle. Sets the angle of the tag.
• Leader. Turn it on to draw a leader from the tag to the duct. Choose Attached End or Free End, and enter a leader length if you want one.

Wide ducts usually take a tag on the duct with the leader off. Narrow ducts usually keep the leader on, so the text does not cover the linework.

To change the arrowhead, select a tag, choose Edit Type, and set Leader Arrowhead. The change applies to every tag of that type.

4. Decide where the tags belong

Revit puts a tag wherever you click, so the drawing standard is yours to apply. These rules cover most offices.

• Tag where the run starts. The reader needs the size at the first duct of a run and at each branch takeoff.
• Tag where the information changes. That means a new size after a reducer or transition, and a new elevation where the run steps up or down. Skip the segments in between.
• Keep tags readable. Horizontal text reads best. Keep tags off fittings and off other tags.
• Stay consistent. Use the same side, the same offset, and the same leader style across the set.

Here is a worked example. A main runs 1000 x 400 for 12 m, then drops to 800 x 400 after a transition, and two branches leave it. You place one tag at the start of the main, one just after the transition, and one at the start of each branch. That is four tags, and the run is fully described. A tag on each of the many segments would add noise and no information.

How do you tag all ducts in a view at once?

1. Open the view.
2. Optional. Select the ducts you want tagged. With nothing selected, Revit tags every untagged element in the view.
3. Go to Annotate, Tag, Tag All.
4. In the Tag All Not Tagged dialog, choose All objects in current view or Only selected objects in current view.
5. Select the tag categories. You can select several, such as Duct Tags, Flex Duct Tags, and Air Terminal Tags, in one pass.
6. Turn on Leader if you want one, and enter a Leader Length.
7. Choose Horizontal or Vertical under Tag Orientation.
8. Click OK.

Three things surprise people here.

• It tags every duct that meets the filter. A plan with long runs ends up with a tag on every segment. Many drafters use Tag All Not Tagged for air terminals and Tag by Category for ducts.
• It skips ducts that already have a tag. Running it again with a different tag type does not add a second tag, such as an elevation tag next to a size tag. If your standard needs two tags on a duct, place the second one with Tag by Category.
• It runs in the active view only. Repeat it in each plan and section.

If a category or a view template hides the tags, Revit shows a message first. Click OK and Revit turns the category on, or opens the Assign View Templates dialog so you can turn it on or remove the template.

How do you tag flex ducts, fittings, and accessories?

Each of these has its own tag category, so each needs its own tag loaded.

• Flex ducts. Load a flex duct tag. Use Tag by Category and click the flex duct, or select Flex Duct Tags in Tag All Not Tagged. A flex duct bends, so tag it near the air terminal end where the reader looks.
• Duct fittings. Elbows, tees, and transitions use Duct Fitting Tags. Most offices tag only the fittings that carry information, such as a transition with a new size.
• Duct accessories. Dampers and similar items use Duct Accessory Tags and usually show a mark or a type.
• Air terminals. Diffusers and grilles use Air Terminal Tags and usually show a mark and an airflow.

How do you tag an angled duct?

Tags follow a duct at an angle only when the tag family has Rotate with component turned on. Revit 2021 made this behavior more consistent between categories. Text inside a rotated tag can still sit slightly off the duct, because Revit cannot center text perfectly at every angle.

You have two choices.

• Turn Rotate with component off in a copy of the tag family. The tag then stays horizontal when you place it, which many offices prefer for readability.
• Leave it on, and check angled tags by eye after you place them.

To edit the family, select a tag, click Edit Family, save a copy under a new name, change the property, and click Load into Project.

How do you change what a duct tag shows?

The tag family decides the content. A duct has a width and a height, or a diameter. It also has top, middle, and bottom elevations, a system, and calculated values such as flow, friction, and velocity. To add flow to a size tag:

1. Select a duct size tag in the model.
2. On the ribbon, click Edit Family.
3. Save a copy under a new name, so the original stays intact.
4. Select the label and click Edit Label.
5. Add the parameters you need from the list, such as Flow. Use Break to put a parameter on its own line.
6. Click Load into Project.

Then select the ducts and pick the new tag in the Type Selector, or load the new tag last so it becomes the default.

How do you tag ducts in a linked model?

Tag by Category works on elements in a linked Revit model. In Tag All Not Tagged, turn on Include elements from linked files.

• The tags live in your host model. The linked file does not change.
• You cannot edit a tag's text to change the linked element's properties.
• If the link reloads or moves, check that the tags still point to the right ducts.

Why does a duct tag show a question mark?

Revit draws a question mark when the tag family cannot read a value from the duct. In Tag All Not Tagged this often shows up on round ducts when the loaded tag was built for rectangular ones. Three fixes work.

• Load a duct tag whose label reads the size for every shape.
• Select only the rectangular ducts. Right-click one rectangular duct, choose Select All Instances, then Visible in View. Run Tag All Not Tagged with Only selected objects in current view.
• Tag the round ducts in a separate command if they use a different tag family or type.

What else goes wrong when you tag ducts?

What else breaks when you tag ducts by hand?

Two problems do not belong to any single step.

Missed tags. A duct that never got a size or elevation tag turns into a question from the contractor. RayCAD keeps a list of anything it could not place, with the reason, and jumps you to it. See how that reduces RFIs.

Model changes. When the design changes, tags drift away from the ducts they describe, and someone retags the affected views. Select the changed ducts and Retag places their tags again, with the same settings.

Teams then try to automate the job, with Tag All, a Dynamo graph, a pyRevit script, a macro, or an AI-written script. Each one reaches the same limit. Placing a tag is easy. Placing it where it reads cleanly, in your firm's layout, across every view, is where they stop. The page on Dynamo and pyRevit and build vs buy show the working method and where it breaks.

How does RayCAD tag ducts end to end?

You pick the views. RayCAD reads the model, decides where tags belong, places them, and lists anything it could not place for you to review. The human moves from placing tags to checking them. That is the difference from a click-saver plugin, which leaves the deciding and the placing with you.

RayCAD covers rectangular, round, oval, and flex ducts, native and fabrication, on floor plans and section views. It places tags inside a duct when they fit and outside, above or below, when they do not. Two layouts ship for each position, and you can import your own. The duct tagging page lists every setting.

What should you check before you issue the sheet?

• Every run has a size tag at its start and after each size change.
• Elevation tags sit where a duct steps up or down.
• Flex ducts, fittings, and accessories carry the tags your standard asks for.
• No tag covers a fitting, and no two tags overlap.
• Section views carry the same information as the plan.
• Tags still match the model after the latest revision.

Try RayCAD on a live duct plan in Revit 2021 to 2027, or email us for a demo. For how long a full set takes by hand and with RayCAD, see the MEPF tagging time report.

What building a duct tagging script yourself really costs

• Time. Whoever builds and maintains the script is doing software development instead of the billable engineering and drafting work they were hired for.
• The AI loop.With Claude or ChatGPT it becomes an endless loop of “fix this”, “now fix that”. Each fix can break a case that worked before, and nobody on the team owns the code.
• Cost. Hours spent building and maintaining scripts, times your hourly rate, against $200 per month for RayCAD for the whole company.

You can build a duct tagging script, and this page shows how. For production MEPF sheets, RayCAD is the cheaper and safer choice. Try it free for 15 days.