Final answer:
According to the NFPA 704 Hazard Identification System, hazard classes with a high fire hazard rating should never have any activity involving fire within 25 feet of them.
Step-by-step explanation:
According to the National Fire Protection Agency (NFPA) 704 Hazard Identification System, there are certain hazard classes that you should never smoke or perform any activity involving fire within 25 feet of. These hazard classes are identified by the top (red) diamond on the NFPA 704 diamond symbol, which indicates the level of fire hazard. Hazard classes that have a rating of 3 or 4 in the fire hazard category should be strictly avoided because they pose an extreme risk of fire. For example, flammable liquids, such as gasoline, and reactive materials, such as explosives, fall into these hazard classes.