Federal rule bars anyone from smoking or carrying a lighted cigarette within 25 feet of a vehicle carrying explosives, oxidizers, or flammable materials. What is the reasoning?
- Smoke can trigger vehicle emissions sensors
- Smoking slows down the loading crew
- It is a general workplace courtesy rule unrelated to the cargo
- An open flame or spark near these materials can ignite vapor or residue and cause a fire or explosion (correct)
Flammable vapor or explosive residue can be present around the vehicle even when the packaging looks intact, and an empty tank that carried a flammable liquid is covered for the same reason. Keeping ignition sources back from the vehicle removes the spark before there is anything for it to find.
Source: 49 CFR 397.13.
A vehicle carrying Division 1.1, 1.2, or 1.3 explosives must not be parked within 300 feet of what, except for brief periods when the necessities of operation require it?
- An interstate rest area designed for truck parking
- Any road with a posted speed limit under 55 mph
- A weigh station
- A bridge, a tunnel, a dwelling, or a building where people work or gather (correct)
The setback targets places where a large number of people would be exposed if something went wrong with the load, which is why it names bridges, tunnels, and occupied buildings. Rest areas and weigh stations built for truck traffic are not what the rule is written to keep explosives away from.
Source: 49 CFR 397.7.
Under the federal segregation table, which pairing generally requires the greatest separation or is prohibited from being loaded together?
- Division 1.1 or 1.2 explosives loaded with an incompatible class such as a flammable liquid or an oxidizer (correct)
- Two packages bearing the same proper shipping name
- Empty packagings that formerly held hazardous materials
- Non-hazardous freight and a single Class 9 package
Explosives are the class least tolerant of heat, shock, and contamination, so the segregation table bars loading them with materials that could feed or set off a reaction. Putting an incompatible class alongside them multiplies the consequences if either package is damaged in transit.
Source: 49 CFR 177.848.
