Measuring Carbon Dioxide (CO2) in Breweries and Wine Cellars

Measuring carbon dioxide (CO2) in breweries and wine cellars is becoming easier, faster, and more reliable every year. During the fermentation of beer, wine, and other products, carbon dioxide is produced in relatively high concentrations. Everyone surely remembers the scene from a cellar or brewery where a candle is burning and must not go out. The candle was previously used as a simple detector of dangerous concentrations of carbon dioxide. 

Units of Carbon Dioxide (CO2) Concentrations

The units of carbon dioxide CO2 concentrations and generally all gases and mixtures can be expressed in two units. The classic unit is percentage. Thus, the ratio of the concentration of the component to the concentration of the entire mixture, multiplied by 100, expresses the concentration in percentage by volume (%Vol.). For toxic gases, even small concentrations are dangerous. However, it would be impractical to express them in hundredths or thousandths of a percent. Therefore, the ppm unit was introduced. Ppm is an abbreviation from the Latin pars per million. It refers to one particle per million particles of the whole. 

100% = 1,000,000 ppm

1% = 10,000 ppm

1 ‰ = 1,000 ppm

Properties of Carbon Dioxide CO2

Carbon dioxide is a colorless, odorless, and tasteless gas. In low concentrations, it is commonly found in the air. CO2 is a highly discussed topic today in terms of global warming. Ten times higher concentrations are measured in terms of air quality in offices, hospitals, or schools. When CO2 concentration increases, combined with increased temperature and humidity, it can lead to loss of attention, fatigue, and sleep disorders. However, during fermentation, concentrations of carbon dioxide increase by another order of magnitude. That is, tens of thousands of ppm CO2. 

Carbon dioxide is 1.5 times heavier than air. This means it stays and accumulates near the floor. This important property must be considered when installing sensors and gas detectors. Established standards prescribe the setting of warning points. The European Commission directive sets the maximum exposure limit at the workplace TWA. For 8 hours, the concentration of carbon dioxide must not exceed 5000 ppm. A short-term limit of 15 minutes is not prescribed in the directive. For assessing air quality, it is necessary to adhere to the EN 13779 standard. 

Formation of Carbon Dioxide CO2 During Fermentation

Carbon dioxide CO2 is formed in nature in various ways. In breweries and wine cellars, it mainly forms during fermentation. During the fermentation process, sugars are converted in the absence of air (anaerobic fermentation) into ethanol and carbon dioxide.

According to Balling's formula, 0.9565 g of CO2 is formed from 2.0665 g of fermentable extract in beer. Young beer binds CO2 only in a limited amount. Therefore, most CO2 is released into the space and subsequently falls to the ground. The most carbon dioxide is produced during primary fermentation, followed by secondary fermentation. Similarly, during the fermentation in wine production, a large amount of carbon dioxide escapes into the space. It is necessary to protect brewery and winery workers from poisoning by this gas.

Carbon Dioxide CO₂ Detection System

The carbon dioxide CO₂ detection system is primarily designed to ensure the safe operation of breweries and wineries. In many small wineries, the long-standing practice of lighting a candle, which goes out when a large amount of CO2 accumulates, is still common. A modern and increasingly affordable approach to ensuring safety consists of individual sensors with optical NDIR sensors, an evaluation control panel, and optical or sound signaling. 

Optical NDIR sensors operate on the principle of the Beer-Lambert law, where certain wavelengths of infrared light are absorbed by the molecules of the measured gas.

The sensor consists of two measuring tubes. Both contain an infrared lamp and an infrared detector. One tube contains a reference gas, usually nitrogen, and the other contains the measured gas. The captured wavelengths of the measured gas are compared with the reference. 

Carbon dioxide is heavier than air, so it stays near the ground. This means, that sensors should be installed as close to the floor as possible. Typically, 10–20 cm above the floor is the ideal placement. The individual sensors then continuously send a signal with the measured concentration to the control panel in the switchboard. The control panel evaluates all concentrations and activates ventilation or warning signaling. 

The setting of the control panel's switching limits is in accordance with legislation and the amount of carbon dioxide emitted during fermentation. The European Commission directive 2006/15/EC sets maximum exposure limits during working hours. According to this directive, it is permissible to reach a concentration of 5000 ppm CO2 for 8 hours.

Short-term exceedance of concentration needs to be monitored for safety reasons. Connecting warning and other safety elements to individual warning limits must be assessed individually for each application. Various elements such as fans, sirens, beacons, and warning signs can be connected to individual switching limits. A test of the entire system's switching can be performed by connecting a button. 

Upon reaching the warning limit of 5000 ppm, the control panel activates the ventilation system connected to it, then at 15,000 ppm, the warning signal lights up, at 25,000 ppm, the sound signal is activated, and at 30,000 ppm, light signs warning people against entering the room are activated. 

The E2618-CO2-50K Concentration Sensor is a member of the new range of multifunctional measuring instruments PluraSens®. For use in breweries and wineries, it is supplied with a temperature-compensated optical NDIR sensor with a range of 0-50000 ppm CO2.

Sensors of the E2618 series are an intelligent solution for modern applications with ModBus RS485 communication and two analog outputs 4-20mA/0-10V.

The CO2 detection control panel is available in versions for 10 sensors or 6 sensors. The control panel is designed for collecting and evaluating information from individual sensors of the detection system. The control panel settings are adapted for use in individual applications. 

The SVN 500 LED Light Sign is one of the possible peripherals for the carbon dioxide detection system in breweries and wineries. When the health-threatening concentration of the monitored toxic gas is exceeded, the detection system transmits the information and lights up the warning sign. The body of the SVN 500 consists of an aluminum profile with an anodized surface finish, red (translucent) and silver (non-translucent) plexiglass walls, and black plastic sides. The LED light sign can be mounted both indoors and outdoors.