Final answer:
Flammable solids specifically refer to substances that can emit flammable gases when heated, a property which is a significant safety concern. Organic solvents are typical examples, and flammability is considered a chemical property.
Step-by-step explanation:
Flammable solids are materials that are easily ignitable and capable of burning rapidly. Specifically, they are substances that emit flammable gases when certain conditions are met, such as when they are heated, which corresponds to option 2 in the given list. These materials can include a variety of chemicals, but most organic solvents fall into this category due to their volatility. Exceptions include some chlorinated solvents like dichloromethane and chloroform, which are less flammable. It's important to note that flammability is a chemical property that refers to a substance’s ability to combust. Also, when dealing with flammable materials, safety is critical as mixtures of solvent vapors and air can explode and solvent vapors, being heavier than air, can travel along surfaces and potentially ignite if they come into contact with a spark or open flame.