Last Updated: 2026-10-02
This article is part of the Print Pro AZ pipe marking series. Start with the pillar guide: The Complete Guide to Pipe Marking: ASME/ANSI A13.1 Explained.
ASME A13.1-2023 introduced Section 4.5, the first standalone abandoned piping section in the standard's history. Any decommissioned, out-of-service, or capped pipe that remains physically in place must be labeled to prevent it from being mistaken for an active system, even if the contents have been fully purged.
That capped line in the mechanical room might be the biggest unmarked hazard on your job site.
Facilities routinely decommission piping without ever updating its markers. The old label showing "ACID" or "NATURAL GAS" stays in place, workers assume the line is still live, or the marker fades and the line gets assumed to be safe. Either scenario creates the conditions for a serious incident.
ASME A13.1-2023 closed this gap with new Section 4.5, dedicated entirely to abandoned piping. If your facility has decommissioned lines still in place, and most do, here's exactly what the standard requires and how to bring those lines into compliance.
What Does ASME A13.1-2023 Section 4.5 Require for Abandoned Piping?
Section 4.5 of ASME A13.1-2023 requires that all abandoned piping remaining physically in place be clearly identified so it cannot be confused with an active system.
The 2023 edition created Section 4.5 specifically for this purpose, replacing the former "Unusual or Extreme Situations" language that left too much room for interpretation. The requirements are direct:
- Abandoned piping must carry a marker designating it as decommissioned or out-of-service
- The designation applies regardless of whether the pipe contents have been purged
- Active-system markers must be removed or covered when a line is taken out of service
- The requirement covers any piping that remains structurally in place and accessible
Key rule from Section 4.5: A purged, capped pipe with no label is still a non-compliant pipe. The absence of markings does not satisfy the standard, absence creates ambiguity, and ambiguity is exactly what Section 4.5 is designed to prevent.
For a complete breakdown of all the 2023 changes, color section revisions, GHS integration, and flow direction requirements, see our ASME A13.1-2023 pipe marker changes overview.
Why Do Unlabeled Abandoned Pipes Create Serious Hazards?
Abandoned piping without clear labeling is one of the most common root causes of maintenance-related injuries in industrial and commercial facilities.
The hazard pattern is consistent: a contractor or maintenance worker encounters an unlabeled line, assumes it's dead, and opens a fitting. What happens next depends on what's still in the pipe. Residual gas pressure, corrosive liquid, or simply contaminated air can injure anyone working nearby.
Here's a scenario Print Pro AZ sees regularly: a facility undergoes a process change, acid lines are capped and bypassed, but the original orange/black "CORROSIVE" markers are left in place. A renovation crew years later sees the old markers, treats the line as active, and spends unnecessary time trying to locate shutoffs. When they finally open the line, they're exposed to residual chemical residue in a supposedly decommissioned system.
The reverse also happens. Unlabeled abandoned lines get tapped by contractors who assume they're utility lines, compressed air, chilled water, and connect equipment to what turns out to be a capped, pressurized hazardous line.
Section 4.5 exists because these incidents happen in facilities of every size and industry. OSHA cites facilities under 29 CFR 1910.144 for inadequate pipe hazard identification, and unlabeled abandoned lines are a primary target during general industry inspections.
How Does ASME A13.1-2023 Define "Abandoned" Piping?
Under ASME A13.1-2023, "abandoned" piping is any line that has been permanently or indefinitely removed from service but has not been physically removed from the facility.
The standard recognizes three distinct categories that Section 4.5 addresses:
| Category | Description | Marking Requirement |
|---|---|---|
| Abandoned | Permanently out of service, contents removed or isolated | Label as "ABANDONED", original content label removed or covered |
| Decommissioned | Formally taken out of service with documentation, may retain residual contents | Label as "DECOMMISSIONED", original hazard information preserved or noted |
| Out of Service | Temporarily inactive, expected to return to service | Label as "OUT OF SERVICE", original content label may remain visible |
The distinction matters for compliance and for safety communication. A line labeled "OUT OF SERVICE" signals a temporary condition, workers know it may be reactivated. A line labeled "ABANDONED" signals a permanent change of status, no reconnection expected, treat as potentially containing residual material.
AHJ and facility auditor note: While ASME A13.1-2023 uses these distinctions, your local AHJ or facility insurance inspector may apply slightly different definitions. Document your facility's classification scheme and apply it consistently. Inconsistency in labeling is as much a citation risk as missing labels.
What Should an Abandoned Pipe Marker Say?
An abandoned pipe marker must include the designation word, "ABANDONED," "DECOMMISSIONED," or "OUT OF SERVICE", and remove or cover any legend identifying the original pipe contents if the pipe no longer carries that material.
The marker text is not optional or decorative. Section 4.5 requires that the designation be the primary readable information on the marker. If the original content legend remains visible, the marker must make clear the line is no longer active.
Minimum label elements for abandoned piping:
- Clear designation: "ABANDONED," "DECOMMISSIONED," or "OUT OF SERVICE"
- If original hazard contents remain or residual material is possible: retain or restate the hazard information
- Cover or remove any active-system direction arrows that no longer apply
- Apply the same durability standards as active-system markers, adhesive must hold for the expected service environment
What color should the label be? ASME A13.1-2023 does not specify a mandatory color combination for abandoned piping. Industry practice uses black text on a white or gray background to signal inactive status, visually distinct from all six active-system color codes. Print Pro AZ recommends confirming your color scheme with your facility manager before ordering, as multi-site operations often standardize on a facility-specific convention.
For pipe and duct markers built to ASME A13.1-2023 specifications, see our pipe and duct marker collection.
Where Do Abandoned Pipe Labels Need to Be Placed?
ASME A13.1-2023 applies the same placement frequency rules to abandoned piping that apply to active systems, at all valves and connection points, at wall and floor penetrations, and at intervals along straight runs.
Placement requirements for abandoned pipe markers:
- At every valve, fitting, or flange, on both sides where accessible from multiple directions
- At every wall, floor, or ceiling penetration, on both sides of the penetration
- At branch connections and tees, on each branch leg near the junction
- At direction changes: elbows, bends, and offsets
- At intervals along straight runs, the standard targets intervals sufficient to identify the line at any point in the run without searching for a label
Why place markers at penetrations? An abandoned line running through a wall may be visible in two different spaces, a mechanical room and an adjacent corridor, for example. A worker in the corridor who can't see the mechanical room side needs to be able to identify the line without walking around the wall.
Do not rely on a single "ABANDONED" label at the cap point. The entire run of the line needs to be marked, particularly in facilities where the line passes through multiple areas or levels.
When Should Abandoned Piping Be Removed Instead of Labeled?
ASME A13.1-2023 states that removal of abandoned piping is the preferred approach, Section 4.5 notes that marking in place is acceptable when physical removal is impractical.
When physical removal is straightforward, accessible lines, low disruption to surrounding systems, no structural complications, remove the pipe. Removed pipe creates zero compliance obligation and zero ongoing safety risk. Marking in place is a permanent maintenance task: labels degrade, get painted over, and fall off. Removal is a one-time action.
Remove when:
- The line is accessible without major structural work
- Removal won't disrupt active systems running nearby
- The facility's renovation timeline includes the area anyway
- The pipe contained hazardous materials with long-term residue risk
Mark in place when:
- Removal would require cutting through insulated walls, ceilings, or slabs
- The line is structurally embedded or load-bearing
- Cost or scheduling makes removal during the current project cycle impractical
- Partial removal is complete but stub-outs remain at penetration points
Document the decision either way. Facilities that experience an incident involving an abandoned line are always better positioned when they can demonstrate a deliberate assessment was made, not just a deferred decision.
What About Gas Lines and Valve Tags on Decommissioned Systems?
Decommissioned gas piping and valve systems require the same Section 4.5 treatment as process lines, with additional consideration for residual pressure and purge documentation.
Gas lines that are capped but not purged are among the highest-risk abandoned piping scenarios. Even at low pressure, residual gas in a line that gets accidentally opened creates a confined-space or ignition hazard. For these lines, the abandoned marker should note "RESIDUAL PRESSURE, DO NOT OPEN" if purge documentation cannot be confirmed.
Valve tags on decommissioned valves should be updated alongside the pipe markers. A valve tag showing "OPEN/CLOSED" on a gas line that's been abandoned sends conflicting signals to a worker who reads the tag without seeing the pipe marker.
For gas line and valve identification products that meet current requirements, see our gas and valve tags collection.
Frequently Asked Questions
Does ASME A13.1-2023 Section 4.5 apply to all piping or only certain systems?
Section 4.5 applies to any piping within the scope of ASME A13.1, aboveground piping visible in normal facility operations, including process lines, utilities, HVAC, and gas systems. Underground piping and certain specialized systems outside the standard's scope are not directly covered, but best practice extends the same abandoned-piping marking logic to any decommissioned line that workers or contractors could encounter.
Do I need to keep the original content label on an abandoned pipe?
If the pipe has been fully purged and no residual material is present, the original content label should be removed or covered, it creates false information about the line's current state. If residual hazardous material may remain, retain or restate that hazard information on the abandoned pipe marker so workers know not to open the line without appropriate precautions.
Is there a required color for abandoned pipe markers under ASME A13.1-2023?
ASME A13.1-2023 does not mandate a specific color combination for abandoned piping. Industry convention uses black text on a white or gray background to distinguish decommissioned lines from all six active-system color codes. Confirm with your facility manager before ordering, particularly if your facility operates multiple sites with a standardized convention.
Can I use a tag instead of a label on abandoned piping?
ASME A13.1-2023 allows tags as an alternative to labels in situations where label application is impractical. For abandoned piping, a durable hanging tag that clearly displays the designation word ("ABANDONED" or "OUT OF SERVICE") can satisfy the requirement. Tags must be secured permanently enough that they can't fall off or be removed accidentally, and they need to meet the same placement frequency rules as labels.
How does OSHA treat unlabeled abandoned piping?
OSHA does not have a dedicated abandoned piping citation standard, but unlabeled abandoned lines are cited under 29 CFR 1910.144 (safety color requirements) and general duty clause violations when they create recognized hazards. Inspectors in general industry facilities routinely identify unlabeled abandoned lines during walk-throughs. The ASME A13.1-2023 Scheme for Identification of Piping Systems standard is the benchmark they use when measuring compliance.
Conclusion
ASME A13.1-2023 Section 4.5 is straightforward: if a decommissioned or abandoned pipe is still physically in place, it needs a marker. The marker must identify the line as abandoned, remove or cover any active-system content labels, and follow the same placement frequency rules as active piping. When removal is practical, remove the pipe, marking in place is an ongoing maintenance obligation, not a permanent solution.
The most common gap Print Pro AZ finds in facility pipe marking audits is exactly this: capped lines with old content markers still attached, scattered through mechanical rooms and utility chases with no indication they're out of service. Getting those lines properly marked takes a few labels, and eliminates one of the most consistent OSHA citation sources in general industry.
Ready to mark your decommissioned lines to ASME A13.1-2023 standards? Shop pipe and duct markers →
Need custom abandoned pipe markers with facility-specific color conventions? 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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