In a modular shipment marked with orange placards, if one of the numbers has an 'x' in front, what does this indicate?

The presence of an 'x' in front of the number on the orange placards indicates that the liquid poses a risk of reacting dangerously with water. This specific labeling is used to warn responders that, upon contact with water, the substance can undergo a chemical reaction that may lead to hazardous situations such as fire, explosion, or the release of toxic gases.

This is particularly important for first responders to know, as proper handling and response procedures will be necessary to ensure safety and mitigate the risks associated with such reactions. Understanding this information is crucial for law enforcement and emergency responders, as it guides them in managing potential hazards during transportation incidents involving these materials.