Requirements for field-applied warning labels
Caution, warning and danger labels that the code requires to be applied in the field must warn effectively, be durable enough for their environment, be permanently attached and not be handwritten, except that variable portions may be filled in by hand if legible.
What the code requires
This rule covers caution, warning and danger signs or labels that the NEC requires to be applied in the field, such as the arc-flash warnings required by 110.16.
Under 110.21(B)(1), the marking must be durable enough to withstand the environment where it is installed and must warn effectively, using words, colors, symbols or a combination of them. Under 110.21(B)(2), it must be permanently attached to the equipment or wiring method and must not be handwritten. An exception allows portions that are variable, or that could change, to be handwritten as long as they are legible.
Informational notes point to ANSI Z535.4 for product safety signs and labels. The 2023 notes also cite ANSI Z535.2 for environmental and facility safety signs, which gives guidance on sign design and placement.
On the job
- A warning label written by hand with a marker does not meet this rule. Required warnings should be printed labels.
- In wet, outdoor or corrosive locations, use a label and an attachment method rated for that environment. Rivets may be needed to keep the sign in place.
- Parts of a required label that vary or may change, such as a date or a calculated value, may be filled in by hand under the exception to 110.21(B)(2), as long as they are legible. The rest of the label must not be handwritten.
What changed in 2023
In 2023 the durability requirement, formerly a separate list item, was merged into 110.21(B)(1), and a new informational note added ANSI Z535.2 for environmental and facility safety signs.
Related sections
- NEC 110.16: Arc-flash warning labels on commercial equipment
- NEC 110.22
- NEC 110.24: Available fault current label at commercial services
- NEC 408.4: Panel circuit directory and labeling
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