Class 1, Class 2.1, and Class 3 materials should not be placed in a trailer with:
The use of cargo heaters is not always permitted. When transporting materials that are categorized as Class 1 (Explosives), Class 2.1 (Flammable Gases), or Class 3 (Flammable Liquids), the use of heaters in the same space is generally prohibited.
This questions appears in the following tests: