Final answer:
The best item to aid in extinguishing smoldering fires in tightly packed combustible materials is a fire extinguisher, especially those with foam or dry powder that can smother the fire and inhibit the chemical reactions.
Step-by-step explanation:
To effectively extinguish smoldering fires in tightly packed combustible materials, it is most appropriate to use a fire extinguisher. Using water on such fires might not penetrate deeply enough and could even spread the fire if the material is floating on water or reactive to it. Sand may be useful to smother small fires but may not suppress a fire that has penetrated deep into the material. A fire blanket might not be large enough to cover the area. Fire extinguishers containing foam or dry powder can effectively smother the fire and inhibit the chemical reactions that allow the fire to continue burning. The foam from fire extinguisher systems foaming plastics, for example, spreads across the burning surface to extinguish the fire.
In contrast, in the context of chemical properties and flammability as mentioned in Exercise 1.4.1B, flammability is a chemical property because it describes a material's ability to ignite and sustain a fire, which relates to chemical reactions between the material and oxygen in the air.