Signal Words

By Michael Johnston | Oct 15, 2014
EC Code Comments 10-2014 Photo 1.jpg




The 2014 National Electrical Code (NEC) has new requirements for field-applied hazard warning markings, signs and labels. Throughout the NEC, rules that required signs, labels and other markings also required a specific signal word be included in the sign, label or marking. Occupational Safety and Health Administration (OSHA) signal words include danger, warning, caution, notice or safety instructions. Use of a signal word or phrase triggers additional requirements that are beyond the NEC, but these words are essential for safety and for communicating the appropriate message with the correct degree of urgency.

ANSI Standard Z535.4 provides guidelines for development of safety signs and labels for electrical equipment. OSHA signal words addressed in the ANSI Z535 standard also have a hierarchy relative to the degree of hazard. This is the sequence of importance:

Danger conveys an imminently hazardous situation that, if not avoided, will result in death or injury.

Warning conveys potentially hazardous conditions that, if not avoided, could result in death or injury.

Caution conveys potentially hazardous conditions or situations that, if not avoided, may result in minor injury or damage, not death or serious injury.

Identified by the signal words, signs and labels must also include a color code, specific details about the hazard, the consequence of interaction with the hazard, and avoidance instruction or procedures. Often, these hazard warnings include a pictogram, which graphically illustrates the hazard and helps communicate the safety message across multiple languages. Product manufacturers and facility owners use the ANSI Z535 marking standards to ensure a safer workplaces and the safe use of their products and equipment.

Hazard warning message content

When it comes to wiring and equipment safety label content, the label, marking or sign should convey the seriousness level of the hazard, the nature of it, how to avoid it and the consequence of interaction with it. For example, a sign in-compliance with these marking requirements could read: 

The colors to be used according to ANSI Z535.1 are as follows:

• Danger: Red

• Warning: Orange

• Caution: Yellow

• Notice: Blue

• Safety Instructions: Green

New NEC requirements

Section 110.21 of the 2014 NEC has been expanded to include specific requirements for field-applied hazard signs, markings and labels. The existing text of 110.21 is retained in subdivision (A), “Manufacturers Marking.” “Field-Applied Hazard Markings” is new subdivision (B). The new requirements read: “(B) Field-Applied Hazard Markings. Where caution, warning, or danger signs or labels are required by this code, the labels shall meet the following requirements.

1. “The marking shall adequately warn of the hazard using effective words and/or colors and/or symbols.”

2. “The label shall be permanently affixed to the equipment or wiring method and shall not be hand written.” 

“Exception to 2: Portions of labels or markings that are variable or could be subject to changes shall be permitted to be hand written and shall be legible.”

3. “The label shall be of sufficient durability to withstand the environment involved.”

The new rules for field-applied hazard markings require effective, consistent hazard warnings using appropriate colors, words or symbols. These markings generally are not permitted to be handwritten, with an exception for portions of the markings or labels that are variable or subject to change, such as markings or labels required by 110.24 or 110.16 require. Handwritten portions must be legible. The markings in (B) also must be durable for the environment in which they are installed. Important aspects of this revision are references to the ANSI Z535.4 standard “Product Safety Signs and Labels” from two informational notes following list items 1 and 3. 

ANSI Z535 uses a standardized approach and specific development criteria for labels and signs that include the signal words. Many existing NEC rules use these signal words in marking and label requirements. These rules have been revised to reference 110.21(B) for development of these signs, labels and markings consistent with ANSI Z535. The change promotes a more consistent approach in developing hazard markings, labels and signs for wiring methods and equipment that exist throughout the Code.

During the 2014 NEC development process, technical committees acted on proposed revisions for new marking and sign rules but also should have determined if the appropriate signal word is used in that particular NEC rule. The development process is a work in progress, and attaining compliance often requires referencing other national standards, such as the ANSI Z535. For more complete information in the ANSI Z535 Safety Alerting Standard, visit

About The Author

A man, Mike Johnston, in front of a gray background.

Michael Johnston

NECA Executive Director of Codes and Standards

JOHNSTON is NECA’s executive director of codes and standards. He is a member of the NEC Correlating Committee, NFPA Standards Council, IBEW, UL Electrical Council and NFPA’s Electrical Section. Reach him at [email protected].






featured Video


New from Lutron: Lumaris tape light

Want an easier way to do tunable white tape light?


Related Articles