What must the emergency response telephone number be according to the 49 cfr section 172.604?

According to 49 CFR Section 172.604, the emergency response telephone number must be a number that is monitored at all times and can provide immediate access to information about the hazardous materials being transported. This number must be listed on the shipping paper and should be staffed by someone who can provide emergency response information. It is typically required to be a 24-hour contact, ensuring that assistance is available at any time.