Why is it necessary to keep hair tied back when operating machinery?

Keeping hair tied back when operating machinery is essential primarily to prevent hair from getting caught in moving parts. Machinery often consists of numerous components that can rotate, spin, or move at high speeds. If loose hair comes in contact with these parts, it can lead to serious injuries or accidents. By securing hair away from the face and machinery, individuals ensure a safer working environment, minimizing the risk of entanglement or other hazards associated with operating mechanical equipment.

The other options don't directly address the primary safety concern related to hair and machinery. While encouraging airflow, avoiding distractions, or preventing overheating can be important in other contexts, they do not specifically connect to the immediate risk management associated with machinery operation.