ANSI Z535.4 and arc flash labels

By Jim Phillips, P.E. founder of

Requirements for arc flash labels are addressed in NFPA 70E, Standard for Electrical Safety in the Workplace, and NFPA 70, National Electrical Code (NEC). To provide additional guidance for the labels, NFPA 70E references the American National Standards Institute’s Z535 Series, known as "Series of Standards for Safety Signs and Tags." The NEC refers to one of the specific standards in that series: ANSI Z535.4 2011, Product Safety Signs and Labels. Its scope sets forth the requirements for the design, application use, and placement of safety signs and labels on a wide variety of products. Without a standardized approach, there might be no uniformity for arc flash labels, and it could lead to confusion for such an important warning regarding electrical hazards.

Label configuration

According to ANSI Z535.4, the label configuration is divided into individual panels and will normally have at least two panels that include the signal word and message panels. Additional panels, such as a safety symbol panel and safety instruction panel, may be included. The label’s panels can be arranged in either a horizontal or vertical format.

Signal word panel: Shown at the top of the label, this panel contains the signal word "danger," "warning" or "caution." The signal word panel precedes the message panel as shown in the image above. The safety alert symbol is also part of the signal word panel and is an equilateral triangle with an exclamation point in the center. It is used to alert people of potential physical injury hazards. A solid triangle shall be the same color as the signal word lettering, and the exclamation mark shall be the same color as the signal word panel background. The safety alert symbol and signal word should be positioned close together and centered in the panel.

Signal words:Since there are no specific requirements about which signal word to use, the selection is based on the meaning of each word and the risk that results from not following the safety message located below the signal word panel.

  • DANGER: This signal word indicates a hazardous situation that, if not avoided, will result in death or serious injury. The use of "danger" should be limited to the most extreme situations. The text uses safety white letters on a safety red background.
  • WARNING: This signal word indicates a hazardous situation that, if not avoided, could result in death or serious injury. The word is spelled using safety black letters on a safety orange background.
  • CAUTION: This signal word indicates a hazardous situation that, if not avoided, could result in minor or moderate injury. This word uses safety black letters on a safety yellow background.

According to ANSI Z535.4, the signal words are uppercase only and shall appear in sans serif font. The signal word should also be larger than the message panel text. As a frame of reference, the size should be at least 50 percent greater than the height of the capital "H" in the majority of the text in the message panel.

Message panel: Located below the signal word panel, the message panel contains a concise and readily understood message regarding the hazard and the action/avoidance. A commonly used message for arc flash labels is "Arc Flash and Shock Hazard—Appropriate PPE Required." The message should be safety black lettering on a safety white background. ANSI Z535.4 also permits safety white lettering on a safety black background, but it is not common for arc flash labels.

Safety symbol panel: This additional panel may be used to contain a safety symbol, which is a graphical representation intended to convey a safety message without relying on words.

Border: According to ANSI Z535.4, the label’s border should be safety white, but safety black is permitted if it is necessary to achieve better contrast.

NFPA 70E 130.5(D) Equipment Labeling: In addition to ANSI Z535.4, NFPA 70E 130.5(D) provides additional requirements for specific information to be listed on a label. This includes the nominal system voltage, arc flash boundary and at least one of the following: the incident energy at the working distance or the PPE category from NFPA 70E but not both, the minimum arc rating of the clothing, site-specific level of personal protective equipment (PPE). Although not required by NFPA 70E, additional information, such as the limited- and restricted-approach boundaries, list of PPE, and equipment name, is sometimes included. Although there may be different variations for arc flash label designs, ANSI Z535.4 provides some basic standardization to help provide consistency and reduce possible confusion.