Incident
A reactor vessel in a specialty chemical plant was shut down for internal inspection. Following standard operating procedures, the vessel was drained, washed, and continuously purged with nitrogen to eliminate flammable vapors. The atmosphere test near the top manway showed 0% Lower Explosive Limit (LEL), and a confined space entry permit was issued. A maintenance technician entered the vessel without a personal multi-gas detector. Within moments, the technician collapsed due to nitrogen asphyxiation. The oxygen level near the bottom of the deep reactor had dropped below 12% because nitrogen is slightly lighter than air but can displace oxygen completely in stagnant pockets.
Contact us – Riskchem – The process safety experts for more details on how to approach such scenarios.
Key Learnings:
- The “Zero LEL” Trap: A reading of 0% LEL only proves the absence of explosive gases; it does not prove the presence of life-sustaining oxygen. Oxygen testing must always accompany flammability testing.
- Stratified Sampling: Confined space atmospheric testing must be conducted at multiple levels (top, middle, and bottom) of a vessel, especially when heavy or light purging gases are used.
- Personal Defense: Entrants must wear calibrated personal multi-gas detectors at all times while inside confined spaces, regardless of what the initial entry permit states.
Labels: Incidents, Confined Space, Occupational Health
