Pollution
Humain
Environnement
Economique

At around 3:25 a.m., the alarms of a carbon monoxide detection system went off at a classified facility near a plant that manufactures ammonia cleaning products. Firefighters detected high carbon monoxide concentrations outside the buildings (up to 120 ppm) and sheltered five employees.

According to their investigations, the nearby plant, which was restarting its units, was the source of the carbon monoxide.

At around 6:00 a.m., the plant’s operator halted the restarting of the units following a technical problem on a furnace. At 7:00 a.m., no more carbon monoxide were detected.

The plant’s internal and external emergency plans were not implemented, but significant resources were deployed (44 firefighters and 10 emergency vehicles).

Focus: Carbon monoxide is a colourless, odourless gas that is slightly less dense than air. A highly toxic asphyxiant gas, it is absorbed by the body in minutes and binds to haemoglobin.

It enters the bloodstream through the lungs and combines with haemoglobin (red blood cells) 200 times faster than oxygen. As carbon monoxide accumulates in the blood, the body becomes increasingly deprived of oxygen.

For guidance purposes, death occurs within one hour of exposure to 0.1% (1000 ppm) of carbon monoxide in the air.

Investigations were carried out in conjunction with the inspection authorities for classified facilities to identify what caused these carbon monoxide emissions. Restarting under close watch was scheduled for the following days.

An analysis of the situation showed that carbon monoxide detection was impaired by hydrogen that had been released during the venting phases of the units’ restart procedure.