ANSI Z535.4: Guide to Effective Product Safety Labeling

Key Takeaways

• Effective product safety signs and labels must clearly identify the hazard, explain the consequence, provide specific avoidance actions, and be visible at the decision point.

• Signal words such as Danger, Warning, Caution, and Notice are selected based on hazard seriousness, injury severity, and likelihood at the specific exposure point.

• ANSI Z535.4 distinguishes product safety signs and labels from facility signs by requiring decals affixed permanently to the equipment wherever it is used.

• Labels must remain legible and durable for the service life of the hazard, with material selection based on environmental factors.

What Makes a Product Safety Label “Effective,” Not Just Compliant?

An effective product safety label clearly identifies the hazard, explains the probable consequences, provides specific avoidance and safety instructions, is visible before exposure to the hazard, and can be understood in seconds.

If a worker must stop and interpret it, it is already too late.

The following example comes from a post-incident investigation I conducted as part of a machinery safety review involving conveyor systems in a manufacturing facility:

A conveyor drive crush injury occurred during routine cleaning. Although the warning label met compliance standards, it was ineffective because the label placement was on the motor housing, behind a guard that workers regularly removed for cleanup. While a label might not have prevented the injury, its purpose is to interrupt routine behavior and encourage safer choices when needed.

What Is ANSI Z535.4 Standard and Why Does It Matter?

ANSI Z535.4 belongs to the ANSI Z535 series, which sets the standards for safety communication so that safety signs, labels, and safety tags remain consistent and easily recognizable across various products and settings. Specifically, ANSI Z535.4 is a practical rulebook for the design, application, use, and placement of product safety signs and labels. 

Product safety signs and labels are warning labels permanently attached directly to a product or piece of equipment to communicate a specific hazard associated with using, servicing, or maintaining that product.

What Counts as a “Product” Under ANSI Z535.4?

Under the ANSI Z535.4 standard, a “product” is identified as:

• • Industrial equipment

  • Manufacturing machinery

  • Power tools

  • Construction vehicles

  • Agricultural machinery

  • Electrical panels

  • Mobile equipment

  • Consumer mechanical products

The ANSI labeling standard distinguishes product safety signs and labels from facility safety signs. Facility signs are installed in a building or work environment, such as wall-mounted exit signs or floor markings. Meanwhile, product safety labels stay with the equipment wherever it goes.

What Are the Core Parts of an Effective Warning Label?

1. 1. Signal Word: The signal word panel is typically at the top of the ANSI label and indicates the level of hazard. The following signal words communicate:

      1. "Danger" signifies an immediate and serious hazard

      2. "Warning" for less immediate risks

      3. "Caution" for lower-level hazards

   2. Hazard Identification: This section should clearly state the nature of the hazard, such as "High Voltage" or "Corrosive Material." This direct information helps workers understand exactly what the danger is, without ambiguity.

   3. Instructional Guidance: Effective labels have a message panel that guides specific actions on how to avoid it, such as "Wear Protective Equipment" or "Do Not Touch." This helps in guiding safe behavior and actions in the presence of the hazard.

   4. Safety symbols and Pictograms: Universal hazard symbols or pictograms are used to convey the message quickly and across language barriers. For instance, a flame pictogram universally indicates a fire hazard, making the warning instantly recognizable.

   5. Language and Text: The safety label's message should be concise and easy to understand, avoiding technical jargon that might confuse the reader. Where necessary, multilingual text can be included to cater to a diverse workforce.

   6. Color Coding: Colors are used to emphasize different parts of the label, enhancing visibility and comprehension. Safety red background is commonly used for high-risk dangers, orange for warning signs, safety yellow background for caution, and blue for general safety information or notices.

How Do I Determine Whether to Use Danger, Warning, Caution, or Notice?

For product safety labels, the signal word isn’t chosen based on how “bad” the machine feels in general. It is chosen based on the specific hazardous situation the label is addressing at the exact point where a person could be exposed during normal use, setup, cleaning, troubleshooting, maintenance, or foreseeable misuse.

You just have to remember: Overusing “Danger” for hazard alerting reduces credibility, and underclassifying risk increases liability.

What Are the Different Safety Labeling Format Options?

The main safety labeling format options are symbol + text, symbol-only, text-only, wordless, and multilingual labels. The right option depends on the hazard, the task involved, and where the product will be used.

Below is a closer look at each format style and when it works best:

1. Safety Alert Symbol + Text Labels

Best default for most equipment because it’s fast to recognize and tells the user exactly what to do. Use it when the hazard requires a clear action, such as during lockout procedures, keeping guards in place, or wearing PPE. The drawback is the space required, especially if you need large text or multiple languages.

2. Wordless (ISO-style) Labels

This format communicates hazards using standardized safety symbols and ISO-style presentation without text. Best for global products where standardized symbols are expected and translation would overload the label. It works only when the symbol meaning is widely understood and the action is straightforward. Not a good fit for hazards that require a procedure.

3. Text-Only Labels

Text-only labels rely entirely on written warnings without a safety symbol panel. It works when you need precise instructions, or there isn’t a good safety alert symbol for the hazard. Useful for small products or tight surfaces. The tradeoff is that they depend on readability, literacy, and language alignment with the workforce, so they can fail if the text is too small or the language doesn’t match the user.

4. Multilingual Labels 

This format includes two or more languages on one label or in paired labels placed side-by-side. They are best when the workforce or customer base speaks different primary languages, and misunderstanding could lead to serious harm. The main downside is crowding. If adding languages forces smaller fonts or cramped layout, the label may become harder to read and less effective.

5. Symbol-Only Labels 

This format uses one or more safety symbols without written instructions. They work best for simple, widely recognized hazards where the safe behavior is obvious, and are useful when language varies and space is tight. The risk is misinterpretation if the symbol isn’t familiar or if the situation requires a specific step that the label can’t communicate without words.

📌 Experts’ Note

"ANSI Z535.4 doesn’t spell out label formats like the Symbol-Only, Wordless, and Symbol and Text, as its 'main' layouts but are still treated as acceptable when they follow ISO conventions."

Now, most product warnings are “hazard alerting” signs and labels. But some labels are different because they also require equipment-specific technical data, not just a general warning or safety information. A common example is arc flash labeling.

How Are Arc Flash Labels Structured Under ANSI and NFPA 70E?

Arc flash labels are structured by combining the required technical data from NFPA 70E with ANSI Z535.4-style hazard warning formatting. NFPA 70E requires arc flash labels to include technical, equipment-specific hazard data based on a documented electrical hazard analysis.

Simply put, NFPA 70E determines the equipment-specific information that must appear on the arc flash label based on an electrical hazard analysis. ANSI Z535.4 influences how the warning message panel is visually organized so the hazard is immediately recognizable.

Where Should ANSI Safety Labels Be Placed?

Place the Label at the Point of Decision

A product safety label should be visible before or at the moment a worker makes a choice that could expose them to the hazard. This is called the decision point. For example:

• • On the outside of an electrical panel door, not inside the cabinet.

  • On the edge of a removable guard, not behind it.

  • At the access opening where hands enter to clear jams.

  • Near the control station where startup occurs.

If a person must already be exposed to read the warning, placement has failed.

Align with the Natural Approach Path

Observe how a person physically approaches the hazard:

• • Do they lean in?

  • Do they crouch?

  • Are they reaching overhead?

  • Are they focused on a control screen?

The label should sit in the natural line of sight during that approach, not where it is convenient for installation. For example, placing a label on the side frame of a conveyor may be compliant, but if workers approach from the discharge end, it may never be seen.

Avoid Hidden or Obstructed Locations

Common placement mistakes include:

• • Behind removable guards

  • Inside panels instead of outside

  • On moving components

  • On horizontal surfaces where dust or oil accumulates

  • Behind piping or cable trays

Labels must remain visible during normal operation and foreseeable maintenance tasks. If routine tasks require removal of parts, consider placing a warning on the removable component itself and at the exposed hazard area.

Consider Viewing Distance and Angle

Placement must account for:

• • Typical viewing height (waist to eye level when possible)

  • Lighting conditions

  • Obstructions

  • Glare from overhead lighting

  • Distance from the task

A label placed too high, too low, or around a corner loses effectiveness. Workers do not scan the entire machine before acting. They look where they are working.

Match Placement to Task Type

Different tasks require different placement strategies:

• • Operation: Place labels near operator interfaces, start buttons, and loading zones.

  • Maintenance and Service: Place labels at access panels, guards, disconnects, and lubrication points.

  • Cleaning and Jam Clearing: Place labels at access openings and removable guard edges.

  • Mobile Equipment: Place labels inside operator compartments and near maintenance access doors.

A product may require multiple labels in different locations to address different exposure scenarios.

How Durable Should Product Safety Labels Be?

Product safety labels should remain legible, attached, and readable for as long as the hazard exists on the equipment. In most cases, that means the label should last for the service life of the product. A faded, peeling, or chemically damaged label no longer communicates risk, even if it was compliant when first installed.

What Materials Are Recommended for Long-Lasting Safety Labels?

Label material selection should reflect real operating conditions:

• • Indoor, dry environments: Standard polyester with permanent adhesive may be sufficient.

  • Washdown areas: Laminated labels with moisture-resistant adhesives are necessary.

  • Outdoor equipment: UV-stable inks and protective overlaminate are required.

  • Chemical exposure: Use chemical-resistant materials tested for the substances present.

  • High-abrasion areas: Consider polycarbonate overlays or engraved/metal plates.

Applying a low-grade label in a harsh environment almost guarantees early failure. However, even high-quality labels degrade over time. They should be inspected during preventive maintenance or equipment safety reviews.

How Does the ANSI Z535.4-2023 Revision Affect Current Safety Labels?

The ANSI Z535.4-2023 revision does not fundamentally change the "look" of the current safety labels like signal words or color coding, but it significantly changes how you are allowed to communicate hazard information. Particularly, two practical changes stand out in this revision:

1. 1. Integration of "Cross-Referencing": Previously, the standard was somewhat rigid about each label being a "stand-alone" warning. The 2023 update explicitly allows safety messages to reference other signs, panels, or manuals.  

      1. Application: If a machine has a complex set of hazards, you can now use a primary hazard label that directs the worker to a more detailed "Safety Instruction" panel nearby. 

   2. New Definition of "Authority Having Jurisdiction" (AHJ): The 2023 version introduces a formal definition for the AHJ, or the person or office responsible for enforcing the requirements of a code or standard.

      1. Application: This provides EHS managers with more leverage when discussing compliance with inspectors or insurance auditors. It clarifies who has the final say on whether a label is "legible" or "properly placed" in a specific local context, helping to resolve disputes over "gray area" compliance.

📌 Experts’ Note

“ANSI Z535.4-2023 expands your options for visual communication and allows labels to work as part of a connected system rather than isolated warnings. If your current labels are in good condition and were compliant with the 2011/2017 version, they generally do not need immediate replacement, as the core design specifications remain consistent.”

5-Point Safety Labeling Effectiveness Scorecard

Over the past two decades of machine safety reviews, I have used a simple five-point scorecard to assess whether a product safety label is likely to be seen, understood, and acted on at the moment of risk. It’s not an ANSI-issued tool, but it reflects what consistently shows up in real facilities. Ask yourself:

1. Can it be understood in 3–5 seconds?

In real environments, people do not study labels. They glance at them, often while already engaged in a task. Look for:

• • Short sentences

  • Plain language

  • No technical jargon

  • Clear visual hierarchy

Red flags:

• • Dense paragraphs

  • Multi-sentence explanations

  • Overly technical terminology

  • Small font size

2. Does it describe the specific hazard?

Generic wording weakens impact. The label should identify:

• • The Energy Source: Electrical, mechanical, thermal, hydraulic

  • The Motion: Rotating, reciprocating, pinch point

  • The Exposure Point: Blade edge, nip point, energized bus bar 

For instance, a warning label that says, “Rotating shaft can entangle clothing” is much stronger and clearer than “Warning: Be careful.”

3. Does it state the real consequence?

Workers respond differently when the outcome is concrete. For example, “May cause physical injury” may be less effective than “Can cause amputation.” The consequence should be realistic, not exaggerated, but specific enough to communicate severity.

4. Does it give clear avoidance action?

A warning without action guidance is incomplete. Look for direct, actionable instructions:

• • “Lockout before servicing.”

  • “Keep guards in place.”

  • “Wear eye protection.”

  • “Disconnect power before opening.”

Avoid vague phrases like:

• • “Use caution.”

  • “Be alert.”

  • “Follow procedures.”

If a new employee could not understand what behavior is expected, the label needs revision.

5. Is it placed before exposure?

This is the most common failure point I see in field assessments. Effective placement means:

• • In the natural line of sight

  • On the access point (guard edge, panel door, control station)

  • Along the approach path

  • Not hidden behind removable components

If the worker encounters the hazard before encountering the warning, the label has already failed. 

📥A printable version of this 5-Point Safety Labeling Effectiveness Scorecard is available for use during equipment audits, PM inspections, and label reviews. It’s designed as a one-page checklist that can be applied at the machine level.

When Does ANSI Z535.4 Require Safety Label Replacement?

ANSI Z535.4 calls for replacing a safety label when it is no longer legible, no longer attached, or no longer accurate for the hazard and how the product is used. To make this easy to apply during routine audits and preventive maintenance, use the triggers below as a quick replacement checklist:

Faded Signal Word: Replace when the header color or signal word can’t be recognized instantly at normal viewing distance.

Adhesive Failure: Replace when edges lift, bubbles form, or the label can be peeled back, since it won’t stay in place or stay readable.

Equipment Modification: Replace or update when guards, access points, controls, or processes change so the label no longer matches the actual hazard exposure.

Hazard Severity Changes: Replace when a change in risk level would justify a different signal word, stronger instructions, or added information.

Workforce Language Shifts: Replace or supplement when the people using the equipment no longer reliably understand the label language.

During an OSHA inspection tied to overhead lifting equipment, the citation’s abatement guidance specifically called out the need to replace missing or illegible function labels on pendant control stations. 

This is a common real-world failure: the equipment may be operable, and the labels may have been correct when installed, but wear, grime, or fading makes the information unreliable in day-to-day use. In other words, labels don’t stay effective on their own. They need to be inspected and replaced as part of normal equipment upkeep.

ANSI Z535.4 FAQs

Are ANSI Z535.4 labels required on all machinery?

No, ANSI Z535.4 labels are not universally “required by law” on all machinery. ANSI Z535.4 is a voluntary consensus standard, meaning it is not a federal law unless specifically adopted by a regulatory body like OSHA or local building codes. However, because OSHA's General Duty Clause mandates a workplace free from recognized hazards, and ANSI standards are often the benchmark for “adequate” warning, following this standard is the industry best practice to minimize liability and ensure worker safety.

Can one safety label address multiple hazards?

Yes, one label can address multiple hazards if it stays clear and readable at the point of use. The risk is that cramming too many hazards or instructions onto one label reduces scanning speed and leads to “label clutter,” especially on equipment with frequent access points. A practical approach is to combine only closely related hazards that occur at the same location/task, and use separate labels when hazards differ by access point or required action.

Do ANSI Z535.4 labels need to be bilingual?

No, ANSI Z535.4 does not mandate bilingual labels in every case. What matters is that the intended users can understand the warning in the time available, which is why many employers and manufacturers choose bilingual or multilingual labels when the workforce or end users are mixed-language. The key is keeping both languages readable.

What’s the best labeling approach for temporary but recurring hazards?

Use durable, repeatable controls such as standardized temporary tags or removable labels placed at the decision point, then remove them when the hazard condition is over. Temporary hazards recur because of tasks, so pair the tag/temporary label with a consistent trigger in the process so it reliably appears when needed. If the hazard is frequent enough that “temporary” becomes routine, it’s usually better to convert to a permanent on-product label.

Are QR codes allowed as a supplement to ANSI Z535.4 labels?

Yes, QR codes can be used as a supplement, as long as the label still communicates the hazard, consequence, and avoidance action without requiring a scan. QR codes are useful for extra details like training video, manual section, and inspection steps, but they should never be the only way a user learns what the hazard is or what to do. Treat them as “more info,” not the warning itself.