According to ANSI/ASHRAE fire safety classifications, which classification indicates the least toxicity and latest flammability?

The classification that indicates the least toxicity and latest flammability according to ANSI/ASHRAE fire safety classifications is A1. This classification is reserved for materials that are considered non-combustible, meaning they do not ignite and burn in air, and they are also deemed to exhibit minimal toxic effects upon exposure. Materials categorized as A1 will not contribute to fire load in a significant manner, making them a safe choice for use in buildings and environments where fire safety is a priority.

In the hierarchy of fire safety classifications, A1 materials represent the safest option available regarding both flammability and toxicity. This makes them suitable for high-risk areas where fire and health safety standards are critical. The other classifications, while they may denote flammability and toxicity levels, do not provide the same level of safety as A1, hence falling short for environments requiring stringent fire safety measures.