Using a “Dangerous” placard is an option, not a requirement. 49 CFR section 172.504(b) permits a transport vehicle hauling non-bulk packages in two or more classes listed in Table 2 to be placarded with DANGEROUS placards. However, this is an option and may be used instead of separate placards for each of the materials in Table 2. While using the Dangerous placard, it should be noted that: The material must be NON-BULK.  The aggregate gross weight of one hazard class onboard loaded at one facility can’t be more than 2,205 pounds.  Remember to always consider basic placarding first and then figure out whether or not you want to use a Dangerous placard. This is because there is a loss of clarity about the hazards in the vehicle.