CO₂ in wineries: a major prevention issue

The risk associated with carbon dioxide in wine-making cellars is well known in the industry, but it is far from being under control. The prevention strategy generally based on natural ventilation, which is random and uncontrollable, is inadequate. Fatal accidents occur every year, and there were 5 in France last year. Faced with one of the deadliest occupational hazards in the sector, several preventive measures can be implemented.

CO₂: an invisible risk

During the winemaking process, alcoholic fermentation naturally generates large volumes of carbon dioxide: 45L of CO2 per litre of must! This gas, which is heavier than air, naturally travels to low points. Very stable, CO2 can remain for long months in areas with low air renewal. While the risk is greatest during the fermentation period, it does not disappear for the rest of the year. Cleaning and devatting operations, or simple tank inspections, can expose workers.

Effective prevention: a six-pronged strategy

1. Capturing CO₂ at source

2. Mechanically ventilate premises and tanks

Only suitable mechanical ventilation can ensure effective air renewal throughout the space, offering optimum and constant efficiency.
Even in a room with wide doors, natural ventilation is not enough, as it is dependent on climatic conditions, unpredictable and uncontrollable, and often impossible at night because of the risk of intruders. The winery must be equipped with a sufficiently sized mechanical system for drawing in fresh air and extracting polluted air, with air outlets being offset by air inlets of equivalent volume.

Mechanical ventilation inside the tanks must be carried out so that the air presents no risk to workers. Two technical solutions can be applied: extraction of the CO2 to the outside by suction, using a centrifugal extractor for example, or sending fresh air into the tank, pushing out the polluted air, using a propeller fan for example.

3. Detect to react in time

Installing fixed CO₂ detectors makes it possible to:

• Continuously detect the level of CO2 in the air ;
• Automatically activate ventilation, when connected to the detection, as soon as the CO2 level exceeds the threshold naturally present in the air (0.03%), so that ventilation only operates when necessary ;
• Trigger a visual and audible alarm when the safety threshold is exceeded.

These detectors must be positioned in sufficient numbers in the areas where CO2 is most likely to accumulate. These devices should be supplemented by portable detectors, worn individually by employees, in the building and in the tanks.
When purchasing these detectors, whether fixed or portable, particular attention should be paid to their technical characteristics. Only detectors using infrared technology have sufficient response time. A very important factor when making your choice is the measurement range, which should extend from 0 to 40,000 ppm or more (i.e. from 0 to 4% or more). Some equipment, often less expensive, is not suitable for use in professional wine cellars because it saturates at 0.5 or 1%.
Finally, remember that the candle or lighter test is completely unreliable, since the flame continues to burn with a level of CO2 that is already lethal to humans.

4. Organising your work

In rooms with specific pollution, such as the winery, and in confined spaces such as vats, work procedures must be formalised in writing. They define precisely how the work is to be organised, the order of tasks, the number of operators (isolated work should be avoided), the equipment to be used, the ventilation times required, the checks to be carried out on CO2 levels, etc.
These procedures must be realistic, adapted to the operation, compatible with the work objectives and brought to the attention of all those involved. To ensure that employees are involved in their own health and safety, and to encourage them to apply the protocols, it is advisable to draw them up with them.

5. Preparing emergency services

As a general rule, it is the employer's responsibility to define instructions for intervention in the event of a workplace accident. CO2 accidents show that 1 in 3 victims seek help!

Providing for the organisation of emergency services meets a twofold challenge: avoiding over-accidents and rescuing victims as effectively as possible. You need to :

• Define the alert procedures, making sure that the means of communication are available and operational, and give clear instructions on call numbers;
• Have the means available for a first level of intervention: presence of workplace first aiders, use of suitable and maintained intervention equipment (self-rescuers to remove oneself from a dangerous atmosphere, for example), employee training, regular practical training exercises;
• Enable emergency services to intervene effectively: responsiveness, accessibility to the accident area, etc.

Emergency procedures must be established, known to everyone and regularly tested. In the event of an accident, every minute counts. Planning and training to intervene encourages responsiveness and the implementation of effective procedures.

6. Training, information and awareness-raising

Everyone who has to work in a winery must be trained in the risks of CO₂: knowing its toxicity, knowing how to use equipment (such as a detector), identifying warning signs, knowing work procedures specific to the operation, knowing procedures in the event of an accident, etc. Training must be adapted to the reality in the field, evolving and updated.

Contact : 
Occupational Risk Prevention Department (P.R.P.) of the MSA Gironde :
05 56 01 97 71 ou 05 56 01 97 52
prp.blf@msa33.msa.fr