Lessons learned from open pit blast fumes causing near-fatal accident in a closed underground drift
Subsequent a quarry blast, at Franzefoss Pukk - section Vassfjell in May 2016, carbon monoxide gas migrated through a 40 m shaft, into a tunnel facility for aggregate production. A TV team from the Norwegian Broadcaster NRK together with employees in Franzefoss Pukk was present in the tunnel during the gas migration. The involved persons got various symptoms from the gas involving sickness, dizziness and some even passed out. Emergency services were alarmed and had to rescue two of the involved individuals. In total, 18 persons ended up at the hospital for health control and treatment. None was permanently injured. Gas exposure was not included in the risk analysis for the TV-team visit, mainly due to no reports of similar accidents were known to the company at that time. Literature search following the incident, did not reveal similar examples. Gas measurements, subsequent the accident blast, show concentrations beyond 2000 ppm, which is above lethal levels. From the subsequent investigation after the gas incident, it seems that different conditions must occur simultaneously for the explosive fumes, to migrate down the shaft. The most important is the distance between the blast and the shaft, and the weather conditions.