A welder is about to enter a storage tank to repair a cracked weld. The tank previously contained a flammable liquid and now has an access opening of 60 cm in diameter, allowing for full body entry. Atmospheric testing has been conducted, indicating oxygen levels are within safe limits, but there are still residual vapours present. What is the most critical additional safety measure required before the welder can enter?

Question: A welder is about to enter a storage tank to repair a cracked weld. The tank previously contained a flammable liquid and now has an access opening of 60 cm in diameter, allowing for full body entry. Atmospheric testing has been conducted, indicating oxygen levels are within safe limits, but there are still residual vapours present. What is the most critical additional safety measure required before the welder can enter?

Answer options: ✅ Ensuring a standby person is continuously present outside the tank and in communication.

• Wearing a full-face welding helmet with a shading lens of at least #12.
• Having a fire extinguisher readily available within 1 metre of the tank opening.
• Confirming that all non-essential tools are removed from the work area.

Correct answer: Ensuring a standby person is continuously present outside the tank and in communication.

Explanation: This scenario describes a confined space entry. A standby person (attendant) is legally required for confined space work to monitor the entrant, maintain communication, and initiate rescue procedures if necessary. While other options are good safety practices, the presence of a standby person is paramount for confined space entry safety, especially with residual hazardous vapours.