Work trousers can be classed as PPE if they’re specifically designed to provide protection against workplace hazards.
For instance, freezer trousers are designed to keep workers warm, comfortable, and safe when working in low-temperature conditions. Meanwhile, FR trousers are designed to protect workers from fire, heat, and related hazards.
On the other hand, standard workwear trousers designed for functionality and comfort wouldn’t usually count as PPE, as they don’t need to meet specific safety standards.