Last year in Germany, which has a good safety record, two workers died in separate incidents at the same brewery.  In the first incident, the owner was found dead with his head and torso in a beer mixing tank. It is thought that, after bottling and subsequent cleaning, he had leaned in to check the container and was overcome by CO2.

 

Just 10 months later a worker was found dead in a pressure tank used to recirculate wheat beer. He had probably forgotten to fit a yeast plug and had leaned into the tank – which was already pressurised with CO2 – to fit one. He was found up to his hips in the container and had been poisoned – probably in seconds – due to the high concentration of CO2.

CO2 is extremely hazardous and can kill in two ways: either by displacing O2, leading to rapid asphyxiation, or as a toxin in its own right. Exposure to as little 0.5% volume CO2 represents a toxic health hazard, while concentrations greater than 10% volume can lead to death. Because CO2 is completely odourless and colourless there is no physical indication of danger usually until it is too late. 

CO2 is a by-product of the fermentation process and, because the gas is heavier than air, it collects at the bottom of containers and confined spaces such as tanks and cellars. It can spill out of tanks and sink to the floor, where it forms deadly, invisible pockets. It is a hazard throughout the brewing process.

Fermentation tanks, beer mixing tanks, silos and other confined spaces are easily accessible – it is rare for them to be fitted with safety interlocks. For this reason rigorous safety systems should be in place and adhered to. Employers must assess the risks these areas pose to their employees and endeavour to prevent them.  

As a rule, entry should not be routine and should only be carried out if absolutely necessary. If entry is necessary suitable safety procedures must be followed.

CO2 from the space must be completely removed. This can be done by discharging all the fermentation and pressure gasses directly into the open air using a ring main system. If this is not possible due to the layout, the CO2 must be manually extracted and safely diverted. 

Prior to entering a tank or other confined space, a ‘release measurement’ of CO2 must be taken using a CO2 monitor. The measurement must be taken by a qualified person, usually by lowering the monitor into the chamber and leaving it there for several minutes.

Anyone entering a tank or other confined space must be equipped with a suitable gas detector. If a certain CO2 concentration is exceeded the device will go into alarm mode with both audio and visual alarms. Generally, at a CO2 volume of 0.5% by volume, a pre-warning is set off; at 1 to 2% by volume the main alarm is activated. With most devices other alarm thresholds can be selected. 

Both portable and fixed CO2 detectors can be used in breweries. Fixed systems typically comprise one or more detector ‘heads’ connected to a separate control panel. If a detector reads a dangerous CO2 level, extractor fans are automatically triggered and sirens or visual beacons can also be activated to warn workers to vacate the area. This sort of installation is suited to larger spaces like cellars and plant rooms.

A lot of work in the brewing industry takes place in more restricted areas where fixed detectors cannot be installed. This means compact portable units are required. Ease of use, with one button operation, should be the norm when it comes to portable detectors. Combining one or more sensors with powerful audible and visual signals to warn when pre-set gas levels are reached, compact portable detectors are easily carried in a confined space, ensuring that pockets of high CO2 concentration are not missed.

If all the safety procedures described above are observed, the risks of dealing with CO2 can be significantly reduced.