CO2 in Fermentation and Brewing

CO2 is the main gaseous metabolic product of fermentation. In breweries and wineries, that means any tank undergoing active fermentation is a continuous CO2 source — and in poorly ventilated spaces, that gas builds up to levels that pose a real risk to personnel. For the general principles of infrared measurement, see the technical note on how to measure CO2.

This note focuses specifically on the safety risk — not on fermentation process control — because it's the most common reason a brewery or winery installs continuous CO2 monitoring.

This note covers

• Why CO2 is a real risk in breweries and wineries
• Which areas concentrate the highest risk
• Which instruments cover each concentration range

Why CO2 Is a Real Risk in Breweries and Wineries

The risk from CO2 isn't direct toxicity but oxygen displacement: as concentration rises, people start feeling fatigued, and at very high concentrations, loss of consciousness or even death can occur. OSHA sets an exposure limit of 5,000 ppm averaged over an eight-hour shift.

During active fermentation, CO2 concentration in a tank's headspace can approach 100% by volume — far above any safe exposure limit. The risk isn't confined to the tank itself: it accumulates around filling machines, in fermentation rooms, barrel cellars, and confined spaces such as sumps, pits, and beer storage tanks.

Which Areas Concentrate the Highest Risk

In breweries, CO2 accumulates naturally in fermentation tanks, around filler machines, and in packaging areas — and particularly in confined spaces (storage tanks, brew kettles, vats, sumps, and pits), where the lack of natural ventilation compounds the risk.

In wineries, the highest-risk areas are fermentation rooms, barrel cellars, and bottling areas. The practical recommendation is to implement continuous measurement in identified risk zones, and to check concentration before entering any enclosed space — because CO2 is odorless and colorless, and levels can become dangerous with no perceptible warning.