Which of the following is a requirement for an emergency eyewash station?

The correct requirement for an emergency eyewash station is that it should provide a constant flow for hands-free usage. This feature is vital because in the event of an emergency, such as exposure to hazardous materials, a person may need to use both hands to hold open their eyes while rinsing them. This ensures that they can effectively flush out any contaminants without having to manually operate the flow of water, thereby maximizing the efficiency and safety of the eyewash station.

A station that allows for hands-free operation ensures that the injured person can focus on rinsing their eyes thoroughly, which is crucial in minimizing potential damage from foreign materials. The other options do not align with the best practices for emergency eyewash stations; for instance, while quick activation is important, the specific requirement is for a hands-free constant flow, which directly addresses the need for effective use during an emergency situation.