Inhalation hazard placards (Division 6.1 PIH or Division 2.3) require:
Correct. PIH (Poison Inhalation Hazard) materials require a primary hazard-class placard plus an "INHALATION HAZARD" subsidiary placard.
CDL Practice Question #251
Category: Hazmat
Why this question matters
This question is one of 68 in our Hazmat bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.