Use this Filter Symbols Legend CAD reference when preparing or reviewing process and piping drawings that show filtration equipment. The sheet groups air, gas, and liquid filter icons in one practical drafting aid, helping teams select a consistent symbol before adding equipment tags, line information, or process notes.
A filter icon identifies the represented equipment category in a drawing; it does not, by itself, define the filter’s construction, performance, connection details, or operating limits. Confirm those details in the project specifications, equipment documentation, and applicable drawing legend. For broader drafting work, pair this resource with references covering P&ID symbols, piping terminology, valve symbols, and pipe and fitting dimensions.
This Filter Symbols Legend CAD sheet is a practical reference for P&ID and process drawings. It includes a variety of standard symbols used to represent air, gas, and liquid filtration equipment, making it easier to keep your schematics consistent and readable across design, construction, and operations teams.
The legend typically includes symbols for:
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General filter and alternative filter symbol styles
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Air filters (including roll air filter / air filter variations)
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Gas filters and cartridge gas filters
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Liquid filters and fixed-bed liquid filter symbols
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HEPA gas filter / high-efficiency filter representation
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Fixed bed air filter symbols
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Rotary filter and rotary liquid filter symbols
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Press filter symbol
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Specialty filter types shown on the sheet such as:
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Biological filter
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Ion exchanger filter
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Oxygen-enriched filter
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“Primary / mid-effect” filter symbol style (as labeled)
Use this CAD legend for:
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P&ID documentation sets and process utility diagrams
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Water treatment, HVAC/process filtration systems
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Standard symbol libraries for drafting teams
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Faster drafting + QA checks for consistent filter notation
How to use the filter symbol reference
Start by identifying the process service shown on the drawing: air, gas, or liquid. Then compare the intended equipment with the corresponding symbol family on the CAD legend. The sheet includes general and alternative filter styles, specialized filter representations, and symbols for equipment such as rotary, press, cartridge gas, and fixed-bed filters.
Use the selected symbol consistently across the P&ID set, utility diagrams, equipment documents, and drafting details. Keep the symbol separate from the information that must be carried by tags, notes, schedules, or datasheets. A symbol can communicate the presence and general type of a filter, while the associated documentation establishes identification, arrangement, materials, maintenance requirements, and process data.
Reference categories included on the sheet
- General filter symbols: useful where the drawing requires a broad filter representation or an alternate symbol style.
- Air and gas filters: includes air filter variations, roll air filter representation, gas filters, cartridge gas filters, and HEPA gas filter notation.
- Liquid filtration: includes liquid filter and fixed-bed liquid filter symbols, along with rotary liquid filter notation.
- Specialty equipment: includes biological, ion exchanger, oxygen-enriched, and primary / mid-effect filter styles as labeled on the source sheet.
- Mechanical arrangements: includes rotary filter and press filter symbols for drawings that distinguish the equipment arrangement.
Drafting and QA checks
Before issuing a drawing, check that the filter symbol matches the equipment description and process service. Confirm that the tag is unique, flow direction is clear, connected lines are readable, and any bypass, drain, vent, isolation, or instrumentation requirements are shown elsewhere in the drawing package when applicable.
Also compare repeated symbols across related sheets. A coordinated symbol library can reduce drafting variation, while a project-specific legend should take precedence when it defines a different convention. This is especially important when CAD blocks are reused between P&IDs, HVAC or process filtration drawings, water-treatment documents, and construction packages.
Related engineering references
For a complete drawing workflow, connect this legend with internal references for process and instrumentation diagrams, CAD block management, equipment tags, line numbering, and piping and fitting reference data. Those resources help bridge the gap between a symbol library and the dimensional or specification information required for design documentation.
Frequently asked questions
What does a filter symbol show on a P&ID?
A filter symbol provides a graphical representation of filtration equipment and helps identify its general type or service. The symbol does not replace the equipment tag, datasheet, specification, or project drawing notes.
Does this CAD legend include air, gas, and liquid filter icons?
Yes. The source sheet includes filter symbol styles for air, gas, and liquid service, as well as several specialized and mechanical filter representations.
Can the symbols be used in any P&ID project?
Use them as a drafting reference, then compare them with the project’s governing legend and drafting requirements. Project conventions should control when they differ from a general CAD reference.
Does a filter icon define the filter’s rating or size?
No. A graphical symbol does not establish filtration performance, physical dimensions, materials, pressure limits, or connection details. Obtain those properties from the approved project documentation.
What should be checked after inserting a filter symbol?
Check the service, equipment tag, flow direction, connected lines, nearby valves or instruments, and consistency with similar symbols elsewhere in the drawing set. Review the completed drawing against the project QA procedure before issue.