For inhalation hazard load, a Class 6 placard (Division 6.1) must be used.  Material can either be poisonous by inhalation or toxic by inhalation. Such materials can be: (1) A gas meeting the defining criteria in § 173.115(c)  (2) A liquid (other than as a mist) meeting the defining criteria in § 173.132(a)(1)(iii) (3) Any material identified as an inhalation hazard by a special provision in column 7 of the § 172.101 table.