Final answer:
The placard that must be used with inhalation hazmat load is the UN number placard.
Step-by-step explanation:
When transporting hazardous materials by inhalation, the placard that must be used is the UN number placard. This placard indicates the specific type of hazardous material being transported. The UN number is a four-digit identifier that is internationally recognized, allowing emergency responders and authorities to quickly identify the nature of the hazardous material in case of an accident or incident.
For example, if you are transporting a load of inhalation hazardous materials such as compressed gas or toxic substances, you would use the placard with the UN number specific to that type of hazardous material.
It is important to note that the use of placards is regulated by the United States Department of Transportation (DOT) hazardous materials regulations, as well as the Environmental Protection Agency's (EPA) hazardous waste regulations.