Which of these is considered a lockout/tagout device?

Lockout/tagout devices are essential components in ensuring the safety of workers during maintenance and servicing activities. A lockout padlock specifically is designed to secure the energy-isolating devices of machinery and equipment, preventing them from being inadvertently energized while maintenance work is being conducted. This type of padlock is often used in conjunction with tags that provide clear communication about ongoing maintenance work.

In the context of lockout/tagout procedures, using a lockout padlock effectively ensures that only the individual who applied it can remove it, which adds an important layer of safety. The main role of such devices is to manage hazardous energy during service activities, thereby protecting employees from potentially dangerous machine start-ups or releases of stored energy.

The other options do not qualify as lockout/tagout devices. Warning signs merely alert personnel to hazards but do not physically control energy sources. Protective barriers might prevent access but do not lock out energy. Noise reduction earmuffs are personal protective equipment for hearing safety and do not relate to controlling or isolating energy sources. Therefore, the lockout padlock is the only device among the choices that fulfills the criteria of being a lockout/tagout device.