What is the only hazardous material allowed to be transported in the passenger compartment?

The only hazardous material allowed to be transported in the passenger compartment is small arms ammunition. This is primarily due to regulations that permit the transport of certain types of ammunition, which are considered to pose a lower risk when properly packaged and labeled. The transportation of small arms ammunition is typically subject to specific guidelines to ensure safety.

In contrast, medical gases, flammable liquids, and radioactive materials have stricter regulations regarding transportation. Medical gases are generally transported in specialized containers, while flammable liquids pose significant fire risks and are usually required to be in a secured and ventilated cargo area. Radioactive materials, being hazardous due to their properties, are also subjected to stringent safety regulations and are not permitted in passenger compartments. Understanding these regulations helps ensure not only compliance with the law but also the safety of all passengers.