16 CFR 1500.15: Labeling of fire extinguishers.

When a substance or mixture of substances labeled for use in or as a fire extinguisher produces substances that are toxic within the meaning of § 1500.3(c) (1) and (2) when used according to label directions to extinguish a fire, the containers for such substances shall bear the following labeling:

(a) When substances are produced that meet the definition of highly toxic in § 1500.3(c)(1), the signal word “Danger” and the statement of hazard “Poisonous gases formed when used to extinguish flame or on contact with heat” are required labeling.

(b) When substances are produced that meet the definition of toxic in § 1500.3(c)(2), the signal word “Caution” or “Warning” and the statement of hazard “Dangerous gas formed when used to extinguish flame or on contact with heat” are required labeling.

(c) Regardless of whether paragraph (a) or (b) of this section applies, any substance or mixture of substances labeled for use as a fire extinguisher that, if applied to an electrical fire, would subject the user to the likelihood of electrical shock shall be conspicuously labeled “Caution: Do not use on electrical wires.”

(d) The statements specified in paragraphs (a), (b), and (c) of this section shall be in addition to any other that may be required under the act. All such substances or mixtures of substances shall also bear the additional statements “Use in an enclosed place may be fatal” and “Do not enter area until well ventilated and all odor of chemical has disappeared.”