Wine growers and brewers – high-risk professions!
We naturally tend to associate gas detection with industries such as oil and gas, while wine or beer making rarely spring to mind. A common mistake is the failure to realise that carbon dioxide is a dangerous gas, because it is found naturally in the atmosphere in very low concentrations (around 400 parts per million or ppm).
CO₂ can be an issu in these confined spaces such as tanks, cellars or bottle storage areas. Therefore health and safety managers must ensure that the correct equipment and sensors are in place.
Description of carbon dioxide or CO₂
Composed of one carbon atom and two oxygen atoms, carbon dioxide, or CO₂, is a linear molecule. In normal pressure and temperature conditions, this compound takes the form of a gas: carbonic gas. It can also be found in liquid and solid form.
It is colourless, odourless and has a higher density than air. It is present naturally in the atmosphere (0.04%) where it poses no risk to the human organism. The human metabolism actually produces CO₂ which is exhaled out through the lungs.
It becomes toxic for our health at volumes of more than 0.5% (5,000ppm) of CO₂. It is a silent, deadly gas that builds up at ground level (it is five times heavier than air) and forms air pockets that gradually increase in size.
To find out more about CO₂, please read through our gas guide: Carbon dioxide
CO₂ poisoning
There are two sources of poisoning due to this gas:
- Asphyxiation: the formation of CO₂ can displace the oxygen contained in the air and pose a risk of asphyxiation for staff;
- Toxicant: the effects on the nervous system further to exposure to high concentrations of carbon dioxide over a prolonged period of time.
The first signs start to appear when you breathe in an atmosphere containing 2% CO₂, with an increase in breathing amplitude. From 20% upwards, respiratory depression occurs, followed by convulsions, coma or even death.
Other effects observed due to the build-up of CO₂: electrical modifications that evoke ischaemia and burns (blisters) at very low temperatures (we talk about dry ice).
Origin of CO₂
Origin of CO₂ in winemaking
The risk of a build-up of carbon dioxide (CO₂) is present at all stage in the winemaking process: from the pressing of the grapes to clarification, aging and bottling. However, it is during the alcoholic fermentation stage that CO₂ concentrations can reach their highest levels (up to 100% volume): there is considered to be around 40 to 50L of CO₂ per litre of wine, and up to 60L for 1L of must at 25°C.
The areas particularly affected are those between the pits, basins and tanks, along with the fermentation rooms, wineries containing wine barrels and bottling rooms. The risk can also be present even when controlled winemaking is not in progress, if the tank, chamber or silo are not rigorously emptied and cleaned.
Origin of CO₂ in beer making / brewing
As with wine, it is the fermentation process by which sugar is transformed into alcohol that produces CO₂. This is a crucial stage in the brewing process and can be broken down into two steps: main fermentation, lasting 3 to 10 days, and secondary fermentation, which depends on the yeast used.
CO₂ produced as a by-product of this reaction is recovered and will be reinjected into beer, fizzy drinks and sparkling wines at a later stage in the process – it gives those drinks their fizziness.
The high-risk areas are the fermentation tanks and the zones near to filling machines, packaging areas and confined spaces.
Safety levels in vineyards, breweries and fizzy drink manufacturering plants
During the active fermentation process, the concentration of carbon dioxide must be monitored in closed buildings before entering, because the concentration levels are likely to exceed the safety levels. People should avoid working in underground tanks if possible, and only skilled individuals who have been declared medically fit for the job should be allowed to perform such tasks.
For people to enter a tank, two conditions are required:
- A constantly breathable atmosphere for the length of time required to perform the task. To guarantee this condition, two actions are required: control the atmosphere of the tank and ventilate it.
- The worker inside the tank must be supervised by a person who remains outside the tank.
For more details, please read through our article: Confined spaces: risks and preventive measures
Pour plus de détails, consultez notre article : Espaces confinés : risques et préventions
1. CO₂ gas detectors
Early CO₂ detection can mean the difference between life and death. That is why it is essential to measure the carbon dioxide rate everywhere there is a risk of CO₂ build-up or leakage. To guarantee the safety of staff, most countries have defined exposure limits: 5,000ppm over an 8-hour work period (8-hour STEL).
It may be better to install a fixed gas detector in larger areas such as factory halls, to ensure that both the area and staff are protected at all times, 24/7. However, to ensure the safety of workers in and around the bottle storage area and in areas classified as confined spaces, a portable detector may be more appropriate. This is especially important for pubs and beverage distribution outlets for the safety of workers and those who are not familiar with the environment, such as delivery staff, sales teams and equipment technicians. The portable unit can be easily fitted to a belt or clothing, and will detect pockets of CO₂ using audible and visual warnings that instruct the user to leave the area immediately.
2. A ventilation system
You will need to install a forced ventilation system, preferably using insufflation. A suction hose takes fresh air from outside the tank if possible, and a delivery hose carries the new air to the tank. The widely used suction technique has some advantages, but its effectiveness is more limited for several reasons: mixing is reduced compared with insufflation; the suction flow is often too low and the end of the suction hose needs to be at the bottom of the tank to ensure maximum effectiveness.
Once the tank has been properly ventilated (at least 15 minutes, or more depending on the fan flow), you will need to make sure the air is really breathable: the CO₂ rate must without exception be under 3%, and as close as possible to the normal rate found in the air (0.04%). There is only one way of getting a precise measurement of the amount of carbonic gas in the air: a detector. A hand-held model is required, preferably using infrared technology. It should be capable of continuously measuring the CO₂ rate.
It is important to stress that the French Labour Code lays down the general measures to be applied for work performed in confined spaces (including tanks): work organisation, ventilation and detection need to be provided for, and the candle test is not legal.
3. Rescue
The statistics about accidents involving asphyxiation in winemaking tanks show that one in three victims were attempting to rescue someone else. Some people believe that, in the event of an accident, it is possible to pull a victim to safety whilst holding your breath. This is extremely dangerous, because performing this kind of rescue operation requires a huge physical effort during which the muscles can use up to six times more oxygen.
In these conditions, it is only possible to hold your breath for 20 seconds at most before reaching breaking point, when the need to breathe becomes irrepressible. A deep breath ensues, unfortunately causing asphyxiation of the rescuer in most cases.
The victim needs to be rescued in under three minutes, the goal being to get the person’s head out of the contaminated air. In order to intervene safely, the rescuer needs to be equipped with self-contained breathing apparatus, or a breathing device connected to a non-contaminated air source. This apparatus must have all the appropriate safety guarantees.
