A welder is tasked with repairing a leaky pipe inside a decommissioned fuel storage tank. Before entry, the tank was purged and tested, confirming an oxygen level of 20.9% and no flammable vapours. However, the space is cramped, and natural ventilation is obstructed. What is the most critical additional safety measure required before permitting welding inside this tank?

Question: A welder is tasked with repairing a leaky pipe inside a decommissioned fuel storage tank. Before entry, the tank was purged and tested, confirming an oxygen level of 20.9% and no flammable vapours. However, the space is cramped, and natural ventilation is obstructed. What is the most critical additional safety measure required before permitting welding inside this tank?

Answer options: ✅ Ensuring a certified confined space attendant is present

• Providing an air-purifying respirator for the welder
• Increasing general area ventilation outside the tank
• Implementing a strict lockout/tagout procedure for adjacent systems

Correct answer: Ensuring a certified confined space attendant is present

Explanation: Even with safe atmospheric readings, a confined space such as a storage tank requires a trained and certified confined space attendant to maintain visual and verbal contact with the entrant, monitor conditions, and initiate rescue procedures if necessary. An air-purifying respirator would not suffice for potential unknown hazards or insufficient oxygen levels, and increasing external ventilation or lockout/tagout (while important for other reasons) does not address the immediate safety of the confined space entry itself.