A worker is instructed to enter a horizontal piping manifold (approximately 1.5 m diameter, 10 m long) to inspect for internal corrosion in a large industrial plant. Which of the following is the most critical hazard to control before entry?

Question: A worker is instructed to enter a horizontal piping manifold (approximately 1.5 m diameter, 10 m long) to inspect for internal corrosion in a large industrial plant. Which of the following is the most critical hazard to control before entry?

Answer options:

• Ensuring adequate illumination inside the manifold.
• Confirming the structural integrity of the manifold. ✅ Preventing the inadvertent introduction of hazardous substances.
• Providing stand-by personnel outside the entry point.

Correct answer: Preventing the inadvertent introduction of hazardous substances.

Explanation: While all listed points are important for confined space entry, preventing the inadvertent introduction of hazardous substances (e.g., through proper isolation and lockout/tagout of all connections) is paramount to prevent immediate atmospheric hazards or chemical exposure inside the confined space. Providing stand-by personnel is crucial but it comes after the isolation of hazards.