Before entering an underground vault, which action is essential?

• A. Ventilate the vault for 5 minutes before entering.
• B. Check the battery of flashlight.
• C. Remove all covers before entry.
• D. Video record the entry.

Answer: (A)

Ventilating the vault before entering addresses the most critical risk in underground vaults: the air you’ll breathe. In confined spaces, gases can accumulate and oxygen levels can be unsafe, so introducing fresh air first dilutes toxic or flammable vapors and helps ensure a breathable atmosphere. This step also supports accurate atmospheric testing and makes it safer to proceed with entry. The other actions—checking a flashlight battery, removing all covers, or video recording—don’t directly improve the hazardous atmosphere or worker safety in the moment of entry.