To inquire into the NLETS Hazardous Materials File, which number should be entered?

To inquire into the NLETS Hazardous Materials File, the UN number is the correct entry. The UN (United Nations) number is a four-digit identification code assigned to hazardous substances, which helps in identifying the material during transport and in emergency situations. It is widely recognized and used internationally in hazardous materials management, making it essential for accurate data retrieval regarding specific substances in the NLETS system.

Using the UN number allows operators to access relevant information about the hazardous material, including details about its properties, safety measures, and emergency response procedures. This is crucial for ensuring public safety and effective emergency response coordination.

In contrast, while other numbers like the CAS number identifies chemical substances but is less relevant in the context of emergency response systems, an Emergency response number generally refers to a hotline or local authority contact rather than a specific hazardous material identifier. The DUNS number, which is used primarily for business identification, does not pertain to hazardous materials inquiries. Thus, the UN number stands out as the most appropriate choice for accessing critical information in the NLETS Hazardous Materials File.