CO2 plays an important role in the expansion of bubbles during bread baking. It is also released from the bread when the bubble walls start to break under pressure, making the porous structure more continuous and open to the outside of the bread. The present study first proposes a method for correcting CO2 measurement from the air replacement taking place in ventilated ovens. Two techniques (infrared detection and gas chromatography) were used and compared. The air flow due to leakage was estimated at 6.9 m(3) h(-1) by injecting a known amount of tracer gas and was shown to have a significant effect on the CO2 concentration measured in the oven atmosphere. Although there was little difference between CO2 detected by infrared and gas chromatography, the infrared-based method was judged to be more convenient and it provided less noisy data. It was thus selected for the rest of the study. The second part of the study investigated the effects of two process parameters on CO2 release: the proving time and the oven temperature. A longer proving time and higher air temperature in the oven significantly affected CO2 release, with a shorter induction period and a greater amount of CO2 released. These results confirmed that CO2 release is a sensitive, key parameter. At this stage, comparison with the simulations from a knowledae model is required to improve the understanding of the combined mechanisms governing CO2 release. The quantitative method developed here is a preliminary step before comparison. (c) 2006 Elsevier Ltd. All rights reserved.