Free AutoCAD HVAC symbols (DWG): diffusers, ducts, dampers, fans, air handling units, valves

About the drawing conventions

There is no single standard for HVAC drawing symbols: air terminals, duct fittings and equipment are drawn in broadly similar ways, but details such as how a damper, a duct riser or a pipe service is shown differ between countries, offices and standards.

These symbols are our own drawings after common HVAC drafting conventions, and the library is not certified against any standard. Check them against your office or client drafting standard and change the blocks if yours differ.

Frequently asked questions

Are these symbols to a drawing standard?

No. There is no single binding standard for HVAC plan and schematic symbols. They follow common conventions and can be changed to match your office standard.

Which units are the blocks in?

Millimetres, at real size. Insert them at scale 1 in a model space that is in millimetres; if your drawing is in metres or inches, scale the blocks on insertion (0.001 or 0.03937).

Can I use the symbols in commercial projects?

Yes. They are free to use and modify in your own projects, including commercial ones. They are provided as is, without warranty.

How do I make a diffuser or equipment schedule from the drawings?

Export the terminal, equipment or valve blocks of all drawings to Excel with BlockSync: one row per block with its tag and attributes. Fill in airflows and capacities in Excel and write them back in one run, with preview and backup.

Can I change a symbol or add attributes?

Yes. Open the DWG, edit a block with BEDIT to change it or add attributes, and save. To update drawings that already contain the block, run ATTSYNC or replace the block. Make a backup first: attribute values can be lost if ATTSYNC is used carelessly.

Where do I find a ready-made set of these symbols for AutoCAD?

AutoCAD itself ships only a small set of sample blocks, so a full symbol set has to come from a library. Download the ZIP on this page and open the DWG: every symbol is a block. Insert one with INSERT (Blocks palette, Libraries tab, then pick the DWG) or drag it from DesignCenter (ADCENTER). You can also download a single symbol on its own.