What is a requirement for a material to be classified as poisonous?

For a material to be classified as poisonous, it is essential that it is known to be toxic to humans. This definition hinges on the established understanding within toxicology that a substance must demonstrate harmful effects on human health when exposure occurs. The classification of a material as poisonous is based on scientific evidence that indicates potential adverse effects, such as acute toxicity or long-term health risks.

In toxicological studies, the degree of toxicity is assessed through various tests and evaluations that determine how the substance affects bodily functions and overall health. A material may fall under the category of poison if, even in small doses, it can lead to significant health issues, proving that the toxicological profile is a crucial factor for classification.

The other options do not provide the necessary foundation for defining a material as poisonous. For instance, a solid can be poisonous, and not all poisonous substances are flammable gases. Additionally, the lack of safety data does not automatically categorize a material as poisonous; safety data is crucial for determining toxicity, not for deeming a material inert.