Date of incident: August 2015
Notice of incident number: 2015158750001
Employer: Agriculture company operating greenhouses

Incident summary
A helicopter was spraying a caustic cleaner to remove whitewash from the windows of an unoccupied greenhouse. A number of workers were working in a grading area adjacent to the greenhouse. There was greenhouse glass above the grading area and some roof vents were open about 10% when the helicopter was spraying. Thirteen farm workers reported to first aid with symptoms of exposure to toxic chemicals. The workers were treated on site by BC Emergency Health Services and also at hospital.

Investigation conclusions

Cause

• Likely exposure to helicopter exhaust gases: The workers' symptoms were more consistent with exposure to combustion engine exhaust gases containing carbon monoxide and nitrogen oxides than with exposure to the cleaning agent. The helicopter was flying at low altitude above the greenhouses. Exhaust gases from the helicopter would be captured by the rotor downwash and pushed downward onto the greenhouse roofs. Vents on the roofs were partially open, and the downwash pressure could have pushed exhaust gases through the vents and into the grading area where the workers were grading. No other sources of carbon monoxide or exhaust gas exposure were identified in the investigation. The workers were most likely exposed to exhaust gases from the helicopter as it flew over the greenhouse roofs.

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