Final answer:
The top rail of a guardrail used for fall protection should be installed at a height of 42 inches from the work surface. Option 3 is correct.
Step-by-step explanation:
The top rail of a guardrail used for fall protection should be installed at a height of 42 inches from the work surface. This is the standard height recommended by safety regulations to provide adequate protection against falls. The top rail serves as a barrier to prevent workers from accidentally falling off the edge and should be positioned at a height that ensures their safety.
When guardrails are used for fall protection, it is essential that they are installed at the correct height for ensuring the safety of individuals working at elevated levels. According to the Occupational Safety and Health Administration (OSHA) standards, the correct height for the top rail of a guardrail system should generally be 42 inches (± 3 inches) above the walking-working surface. This regulation ensures that adults of varying heights are protected from accidental falls.