Last Updated: 2026-10-02
ASME A13.1-2023 updates the national standard for piping system identification, approved by ANSI on August 18, 2023. Key changes include a revised color section with six standard hazard-based combinations, formal GHS pictogram integration, a new Abandoned Piping section, and a shift to continuous-maintenance, replacing the fixed revision cycle used in prior editions.
Your pipe markers may be out of date, and you might not know it.
ASME A13.1-2023 was approved in August 2023, and most facilities haven't caught up. If your markers still reflect the 2020 edition, or older, you're running gaps that OSHA inspectors and facility auditors will find. Wrong color combinations, unlabeled abandoned lines, and missing flow direction arrows are the most common citation sources.
This guide breaks down every change in the ASME A13.1-2023 edition: what's new in the color section, how GHS pictograms now fit the standard, what continuous-maintenance means for your update cycle, and what the new abandoned piping requirements mean for decommissioned lines in your facility.
What Is ASME A13.1 and Who Needs to Follow It?
ASME A13.1 is the national standard for piping system identification, it defines the color, text, size, and placement rules for pipe markers across industrial, commercial, and institutional facilities.
The standard covers all aboveground piping visible in normal facility operations: process lines, utilities, HVAC, fire suppression, gas lines, and more. Underground piping and certain specialized systems fall outside its scope.
Who references A13.1?
- OSHA incorporates it under 29 CFR 1910 for general industry
- Facility auditors and insurance inspectors use it as the compliance benchmark
- Electrical contractors working on industrial job sites encounter it on mechanical systems
- Fire protection professionals rely on it to identify suppression system lines
While A13.1 is a voluntary consensus standard, OSHA's adoption makes it the enforceable benchmark in most facilities subject to general industry regulations. When an inspector finds unlabeled or incorrectly marked piping, A13.1 is what they measure against.
For the full pipe marking rules, label size, placement frequency, and text requirements, see The Complete Guide to Pipe Marking: ASME A13.1 Explained.
What Changed in the ASME A13.1-2023 Color Section?
Both the Color section and Table 4.2-1, "Designation of Colors," were revised in the 2023 edition, the part of the standard most contractors and facilities managers reference daily.
The current edition defines six standard color combinations based on hazard characteristics, plus four user-defined combinations your facility can customize for non-standard contents:
| Color Combination | Pipe Contents |
|---|---|
| Yellow / Black text | Flammable, combustible, and oxidizing fluids and gases |
| Green / White text | Water (potable, cooling, boiler feed, fire service) |
| Blue / White text | Compressed air |
| Red / White text | Fire-quenching fluids and suppression systems |
| Orange / Black text | Toxic, poisonous, or corrosive fluids |
| Brown / White text | Combustible fluids (non-flammable petroleum liquids) |
Critical rule: Color alone does not comply. ASME A13.1-2023 requires color to be used in combination with a legend, the text that identifies pipe contents. Color bands without a legend text fail the standard.
The four user-defined combinations let your facility designate custom color pairs for piping that doesn't fit standard categories. These must be documented in your facility's pipe marking plan and applied consistently.
For a printable color reference, see our ASME A13.1 pipe marker color code chart.
Practical action: If your installed markers predate the 2023 edition, compare them against the updated Table 4.2-1. Discrepancies in user-defined categories are the most common gap Print Pro AZ finds when facilities run a pipe marking audit.
How Does GHS Integration Work in the 2023 Standard?
ASME A13.1-2023 formally repositioned GHS pictograms within the standard, moving them from former Figure 4.1-1 to the new Figure 4.1-4, titled "GHS Pictograms."
GHS (Globally Harmonized System of Classification and Labelling of Chemicals) pictograms are the internationally recognized hazard symbols: the flame, skull and crossbones, corrosion symbol, exclamation mark, and others. The 2023 edition clarifies when and how these apply to pipe markers.
The standard's GHS rule:
- GHS pictograms on pipe markers are optional, not mandatory
- Apply them where piping connects to containers already labeled under GHS requirements
- When used, the pipe label may include: product identifier, pictogram, signal word, and hazard statements
- Elements must match what's on the connected container
When to use GHS pictograms on pipe markers:
- Chemical process piping connected to GHS-labeled drums, totes, or tanks
- Acid or caustic piping in facilities with a unified GHS chemical management program
- Any system where a worker could confuse the pipe hazard with the adjacent container label if pictograms were omitted
Note for multi-site operators: If your company has standardized on GHS labels for containers, aligning your pipe markers with those labels is a best practice, even where the standard leaves it optional. Consistent hazard communication across containers and piping reduces error.
What Does "Continuous Maintenance Standard" Mean for Your Facility?
The shift to a continuous-maintenance standard is the biggest structural change in ASME A13.1-2023, and the one most facilities teams don't know about.
Prior to 2023, ASME A13.1 operated on a periodic-maintenance cycle: the committee reviewed and revised the full standard on a fixed schedule, publishing a new edition roughly every five years (2015, 2020, 2023). Each update required completing the entire standards development process from start to finish.
What changes under continuous maintenance:
- The ASME A13 Committee can approve targeted amendments at any time
- Individual sections can be updated without waiting for a full edition revision
- ASME publishes amendments incrementally, your 2023 copy may already have posted addenda
What this means for your pipe marking program:
- Check the ASME A13.1 standard page periodically for amendments and errata rather than waiting for a new edition
- Reference the current version of A13.1 in your compliance documentation, not just an edition year
- When purchasing pipe markers, ask your supplier to confirm they're building to the current version including any addenda
This model mirrors how other living standards handle interim changes, the standard is now a rolling document, not a five-year snapshot.
What Are the New Flow Direction and Legend Requirements?
The 2023 edition added three new figures to standardize how flow direction arrows appear on pipe markers, a gap prior editions left to facility interpretation.
The three new figures:
- Figure 4.1-1: Flow Direction to the Right (single arrow)
- Figure 4.1-2: Flow in Both Directions (double-headed arrow)
- Figure 4.1-3: Flow in Both Directions (arrows pointing in opposite directions)
Before the 2023 edition, facilities handled flow arrows inconsistently across sites. An inspector walking a multi-building campus would find different arrow conventions in each building and had no clear standard to cite. Now they do.
Paragraph 4.3 was also expanded to specify that legends should be applied close to valves or flanges. The 2023 edition includes provisions for situations where this placement is impractical, for example, where thermal insulation or equipment blocks label placement near a connection point.
Standard placement requirements remain:
- At all valves and flanges (both sides if accessible from two directions)
- At branch connections and tees, on each branch leg near the junction
- On both sides of wall, floor, and ceiling penetrations
- At direction changes: elbows, bends, and offsets
- At frequent intervals on straight runs (industry standard: every 25-50 feet)
For pipes above normal line-of-sight, place the label below the horizontal centerline so it reads from floor level.
How Should Abandoned Piping Be Marked Under ASME A13.1-2023?
ASME A13.1-2023 replaced the former "Unusual or Extreme Situations" section with new Section 4.5, "Abandoned Piping."
Abandoned piping is decommissioned or out-of-service piping that remains physically in place. In older industrial buildings, abandoned lines are routinely mistaken for active service lines, creating serious safety hazards when workers connect to or open a line that contains residual hazardous material.
Section 4.5 requires:
- Clear identification of abandoned piping so it cannot be confused with active systems
- Marking must designate the pipe as decommissioned or out-of-service
- The requirement applies even if pipe contents have been purged
Here's a situation Print Pro AZ sees regularly: a facility expansion leaves behind legacy gas or acid lines that were capped but never re-labeled. Workers on a renovation project open a fitting assuming the line is inert, it isn't. Section 4.5 addresses exactly that gap.
For gas and valve line identification that meets the 2023 requirements, see our gas and valve tags collection.
Practical step: Walk your facility and identify any capped, unused, or decommissioned lines that still carry active-system markers, or no markers at all. Those are your Section 4.5 compliance gap.
ASME A13.1-2023 vs. 2020: Quick Comparison
| Feature | A13.1-2020 | A13.1-2023 |
|---|---|---|
| Maintenance model | Periodic (fixed edition cycle) | Continuous (rolling amendments) |
| Color section | Table 4.2-1 | Table 4.2-1 (revised) |
| Standard color combinations | 6 + 4 user-defined | 6 + 4 user-defined (updated) |
| GHS pictograms | Former Figure 4.1-1 | New Figure 4.1-4 |
| Flow direction figures | Not standardized | 3 new figures (4.1-1, 4.1-2, 4.1-3) |
| Abandoned piping | "Unusual or Extreme Situations" | New Section 4.5 "Abandoned Piping" |
| Legend placement | Paragraph 4.3 (basic) | Paragraph 4.3 (expanded with impractical-placement provisions) |
| Scope and definitions | 2020 edition | Revised in 2023 |
Frequently Asked Questions
Is ASME A13.1-2023 mandatory?
ASME A13.1 is a voluntary consensus standard, but OSHA references it under 29 CFR 1910 for general industry. In practice, it functions as the enforceable benchmark for pipe marking in most industrial and commercial facilities. When an OSHA inspector cites unlabeled or incorrectly marked piping, A13.1 is the standard they measure against.
What are the ASME A13.1-2023 pipe marker color codes?
The 2023 edition defines six standard combinations: Yellow/Black (flammable/oxidizing), Green/White (water), Blue/White (compressed air), Red/White (fire-quenching), Orange/Black (toxic/corrosive), and Brown/White (combustible). Four additional user-defined combinations are allowed. Color must always be combined with a legend text, color bands alone do not comply.
How often should I update my pipe markers to stay current with ASME A13.1?
Now that A13.1 is a continuous-maintenance standard, check the ASME A13.1 page for posted amendments rather than waiting for a new edition. When ordering replacement markers, confirm your supplier builds to the current version including any addenda. A full re-marking audit every 3-5 years is good practice, or whenever your facility undergoes major renovation or piping changes.
Do GHS pictograms need to be on every pipe marker under the 2023 edition?
No. ASME A13.1-2023 makes GHS pictograms optional. Apply them where piping connects to containers already labeled under GHS, such as chemical process piping tied to GHS-labeled drums or totes. When you include them, align the pictogram, signal word, and hazard statements to match what's on the connected container.
What does Section 4.5 require for abandoned piping?
Section 4.5 of ASME A13.1-2023 requires that decommissioned, abandoned, or out-of-service piping be clearly identified so it cannot be mistaken for an active system. Any capped or disconnected line that remains physically in place needs a marker designating it as abandoned, even if the contents have been purged.
Conclusion
ASME A13.1-2023 tightened requirements across color coding, GHS integration, flow direction marking, and abandoned piping identification, and moved to a continuous-maintenance model that allows the standard to be updated at any time. If your facility is still running 2020-era or older markers, a gap audit is overdue.
The most common gaps Print Pro AZ sees: abandoned lines still carrying active-system markers, color combinations that predate the revised Table 4.2-1, and missing flow direction arrows on bidirectional runs. Getting those right protects your team and keeps you clear of OSHA citations.
Ready to bring your pipe markers up to the 2023 standard? Shop ASME A13.1-compliant pipe and duct markers →
Need custom colors for your facility's user-defined combinations? Order custom pipe markers →
Questions? Call Brent: (602) 649-5305
Brent Hanke | Print Pro AZ | (602) 649-5305 | b.hanke@printproaz.com Brent Hanke is the founder of Print Pro AZ, supplying NEC-compliant labels to contractors across the country.
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