Why “Do Not Open” Lockout Tags Matter for Valve Safety
In industrial environments, a single valve can be the difference between a safe workday and a deadly accident. When maintenance or servicing is underway, “Do Not Open” lockout tags are critical for warning workers not to open valves that isolate hazardous energy sources.
These tags aren’t optional. OSHA mandates them under its Control of Hazardous Energy standard (29 CFR 1910.147). If you're in charge of safety, maintenance, or operations, understanding when, why, and how to use “Do Not Open” tags isn’t just smart - it’s legally required and could save lives.
What Does “Do Not Open” Really Mean?
A “Do Not Open” tag is a tagout device applied to a valve to clearly signal that it must remain closed. It’s often used in tandem with a lockout device (like a cable, hasp, or cover), but the tag itself serves a crucial role: it communicates risk.
Per OSHA 1910.147(c)(5)(ii)(C), tags must include language such as “Do Not Open” to warn of hazardous conditions if the valve is moved.
When someone applies this tag to a valve, they’re saying: do not energize, pressurize, or release anything through this point - serious injury or death could result.
Common Valve Applications for “Do Not Open” Tags
These tags are heavily used in any facility where pressurized or hazardous media flows through pipelines. Examples include:
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Oil & Gas: Isolation valves on pressurized pipelines, wellheads, or processing units.
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Chemical Processing: Inlet/outlet valves on reactors, tanks, or chemical lines.
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Water Treatment: Chlorine injection valves, sludge lines, influent/outlet controls.
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Food & Beverage: CIP system valves, pasteurizer shutdowns, steam isolation.
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Power Plants: Steam valves, condensate lines, feedwater systems.
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Manufacturing: Air, hydraulic, or coolant valves on machines under repair.
If a valve controls hazardous energy or material and someone’s working downstream, it must be locked and tagged to prevent accidental opening.
Real Consequences: Incidents Involving Unsecured Valves
Here are real-world examples where a simple tag could have saved lives:
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Gas Utility Explosion (Indiana) – A worker was killed when a valve was opened prematurely during maintenance. Pressurized gas caused a pipe elbow to spin and strike the worker in the head. No tag was present.
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Texas Refinery H₂S Release – A contractor died when hydrogen sulfide gas leaked through a closed but untagged and improperly sealed valve. Had it been correctly locked and tagged with “Do Not Open,” the danger would’ve been clearly communicated.
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Steam Trap Fatality (U.S. Power Plant) – A worker servicing a steam line was fatally scalded when a valve was left open. No visible tags or locks were applied to indicate the line was energized.
These are just a few among hundreds of cases OSHA and NIOSH investigate each year. In most, the conclusion is the same: proper lockout/tagout would have prevented the incident.
What OSHA Requires
The governing regulation is 29 CFR 1910.147. Here’s what matters for valve tagout:
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Energy isolation is required when servicing equipment could expose workers to unexpected energy or material.
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Tags must clearly warn not to operate, open, or energize.
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If a valve can be locked, it must be locked and tagged. Tagout alone is only allowed if lockout isn’t possible.
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Tags must be durable, standardized, and identifiable, with the name of the person who applied it.
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Only the person who placed the tag (or an authorized supervisor following formal protocol) may remove it.
Failure to follow these rules opens the employer to major citations - and worse, leaves workers at risk.
ANSI’s Role
While OSHA is the law, ANSI provides best practices. Specifically:
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ANSI Z244.1 (Control of Hazardous Energy) supports OSHA’s framework and encourages risk-based enhancements.
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ANSI Z535.5 (Safety Tags) standardizes the appearance of tags, including color, signal words (like DANGER), and iconography.
Using ANSI-compliant tags (red/white DANGER headers, clear “Do Not Open” messaging) ensures visual clarity and aligns with recognized safety norms.
Why Tags Alone Aren’t Enough
OSHA makes it clear: a tag is a warning, not a physical restraint. That's why locks are required on valves that can accept them. Tags support locks by explaining why the valve is secured and who’s responsible.
In valve applications, a tag alone is not a substitute for mechanical isolation unless it’s truly impossible to apply a lock - and even then, employers must implement additional protective measures (e.g., valve handle removal, supervision, secondary signage).
Legal and Financial Fallout
Beyond injuries and death, companies that skip proper tagout face:
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Fines: Up to $16,550 per serious OSHA violation - and much higher for willful or repeat offenses.
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Civil liability: Families of injured or killed workers may sue, leading to multimillion-dollar settlements.
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Production losses: One valve opened too soon can shut down an entire facility - or worse, cause an explosion.
Locking and tagging valves may feel tedious, but not doing it can be catastrophic.
Conclusion
“Do Not Open” tags on valves aren’t optional. They are a clear, simple tool that prevents accidents, ensures OSHA compliance, and saves lives. When workers see that tag, they know a serious hazard lies behind that valve - and they know not to touch it.
If your facility handles pressurized systems, chemicals, or steam, your lockout/tagout program isn’t complete without properly worded, ANSI-style “Do Not Open” tags that hold up under real-world conditions.
We provide OSHA-compliant lockout tags — including “Do Not Open” options — built for valve safety. Durable, visible, and ready to be deployed across your facility.