A leak of 500 l of ethyl acrylate (C5H8O2, hazardous and flammable, highly volatile with a characteristic odour) was detected on a 1 m³ plastic IBC at around 4:50 p.m. at a storage area of a chemical plant. The ethyl acrylate flowed into the catchpit, where it partially evaporated. The operator initiated its internal emergency plan. A response crew used a monitor nozzle to create a water spray to knock down the vapours. The storm water system was diverted to a retention basin. The water spray was shut off at around 5:35 p.m. as the ethyl acrylate had mass polymerized in the catchpit and was no longer releasing vapours. The solid polymer was placed into a drum to be disposed of at an approved facility. The internal emergency was lifted at around 6:30 p.m. Having brought the leak and vapours under control within 30 minutes, the operator informed neither the firefighters nor the authorities. However, as early as 5:30 p.m. emergency services had been contacted by local residents who, alerted by the unpleasant smell (ethyl acrylate has a very low odour-detection threshold of 1 ppb), called to report a gas leak. The residents of two buildings were told to stay indoors. More than one hour passed before the firefighters learned the real reason for the smell and allowed them to go outside.

The incident was caused by accidental exothermic polymerisation inside the IBC, which subsequently became damaged and was no longer sealed. After an analysis of the incident, it was assumed that polymerisation of the ethyl acrylate was initiated while it was being packaged at the supplier’s premises. However, this polymerisation may have been promoted by other factors, as the ethyl acrylate was stored outdoors in a transparent IBC (light and heat are catalysts). The operator changed its storage conditions. IBCs are now stored in an enclosed area, only reinforced IBCs with opaque walls are used, and smaller volumes are stored. Investigations are being conducted to check the product’s stability according to the temperature and inhibitor content. The site’s internal emergency plan has been modified so that the firefighters and authorities are systematically informed when it is implemented.