Many OSHA standards, such as 1926 subpart P for trenching and excavation, require a competent person to be onsite and perform certain activities. For example, during trench construction, a competent person must classify the soil and inspect the trench at the start of each shift and whenever conditions change to ensure there’s no risk of a cave-in. When a trench or other excavation requires a protective system, the competent person must have the requisite knowledge to choose an appropriate one.

RELATED: How to Choose the Right Trench Protective System

OSHA defines a competent person as "one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them."

An existing hazard could be, for example, a trench that lacks adequate ventilation or a safe means of entry and egress.

For scaffolds, a competent person should be knowledgeable about factors that could affect the structural integrity of the scaffold and be able to evaluate the effects of events such as a dropped load or a truck backing into a support leg.

It’s up the employer to determine whether an employee has the skills, knowledge and experience to perform the role of a competent person. OSHA does not specify training requirements for competent persons, only the knowledge they must have.

Of course, someone may be deemed a competent person for certain activities and not others.

“There’s a misunderstanding at some companies that someone designated a competent person for one activity is automatically a competent person for another,” said Tina Davis, a United Rentals representative with the Trench Safety group. “A person might know everything they need to know about trench safety and shoring, for example, but not necessarily be qualified to inspect scaffolding, conduct a fall hazard analysis or inspect personal fall arrest systems.” For that reason, a large jobsite may require more than one competent person.

While training doesn’t automatically make someone a competent person, it’s often necessary. United Rentals offers a wide range of safety training classes and is the largest provider of trench safety training programs, with training available in the classroom and online.

Marianne Wait is an editor and writer who creates content for Fortune 500 brands.