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Heavy Equipment Operator Certification Exam Prep · Question

An emergency response team is preparing to enter a process vessel that has been isolated and vented, but previously contained a highly flammable solvent. What is the critical atmospheric test that must be performed first, in addition to oxygen levels?

Even after venting, residual flammable vapours can be present in a confined space that previously contained solvents. The most critical atmospheric test, alongs

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Question: An emergency response team is preparing to enter a process vessel that has been isolated and vented, but previously contained a highly flammable solvent. What is the critical atmospheric test that must be performed first, in addition to oxygen levels?

Answer options: ✅ Flammable gas/vapour concentration (LEL - Lower Explosive Limit).

  • Carbon dioxide (CO2) levels.
  • Sulphur dioxide (SO2) levels.
  • Nitrogen (N2) levels.

Correct answer: Flammable gas/vapour concentration (LEL - Lower Explosive Limit).

Explanation: Even after venting, residual flammable vapours can be present in a confined space that previously contained solvents. The most critical atmospheric test, alongside oxygen levels, is the Lower Explosive Limit (LEL) to ensure the atmosphere is not explosive before entry, as per confined space entry regulations and CSA Z1006-16.

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