Conveyors should be equipped with which of the following?

The answer

Under OSHA's construction standard for conveyors, 1926.555, a conveyor should be equipped with an audible warning signal that is sounded immediately before starting up, along with emergency stop devices and guards protecting workers from nip points and other moving parts. If a multiple-choice item offers 'all of the above' covering these devices, that is the intended answer, because the standard requires each of them, not just one.

The reasoning is about how conveyors injure people. They start remotely and without warning, they have pinch/nip points where the belt meets pulleys and rollers, and they move continuously — so a worker caught in one has seconds at most. OSHA's requirements each address one of these hazards: the audible warning gives people time to clear the line before it moves, the emergency stop lets anyone halt the system instantly when something goes wrong, and guards physically keep hands and clothing out of the danger zones.

The specific requirements

1926.555(a) sets out the essentials. (a)(1): Means for stopping the motor or engine must be provided at the operator's station, and conveyors that could injure workers must have an audible warning signal sounded immediately before starting up. (a)(2): If the operator's station is at a remote point, similar stopping controls must be available at that station too. (a)(3): Emergency stop switches must be arranged so the conveyor cannot be restarted until the actuating stop switch has been reset to the running/'on' position. (a)(4): Screw conveyors must be guarded to prevent employee contact with turning flights. And (a)(8): all crossovers, aisles, and passageways must be conspicuously marked.

Why partial answers fall short

Only an audible warning. Necessary but not sufficient. A warning tells people the belt is about to move, but it does nothing once the belt is running and a hand is drawn toward a nip point. You still need e-stops and guards.

Only an emergency stop. Also required, but a stop control is a last resort that depends on someone reaching it in time. Guards prevent contact in the first place, and the warning prevents the surprise start. One device can't replace the layered protection the standard demands.

Only guards. Guards protect fixed nip points, but they don't warn of start-up or give a way to kill power in an emergency elsewhere on the line. Guarding alone leaves the start-up and shutdown hazards unaddressed.

The bigger picture: crossing and control

Workers should never climb over, reach across, or crawl under a moving conveyor; instead they should use marked crossovers, aisles, and passageways (required by 1926.555(a)(8)). Emergency stops must be designed so that after activation the conveyor cannot simply be restarted from another station — the stop must be reset first. These design details reflect the standard's philosophy: assume the machine will surprise someone, and build in warning, guarding, and a reliable way to stop it. Because the standard requires the warning, the e-stop, and the guarding together, the complete 'all of the above' option is correct.