Introduction and objectives In the short history of ergonomics (approximately 50 years) there have been notable changes in the atmosphere that we breathe, such as large, medium and small particles, as well as the gas composition, with increases in carbon dioxide (CO 2) of about 125%. This situation becomes worse within the buildings where the physiology exercise laboratories are located. The objective of this study was to determine how these atmospheric changes affect humans during exercise. Methods A comparative study was conducted by means of 2 paired ergometric bicycle tests on 13 subjects (12 males and 1 female). One was carried out in the normal laboratory situation (indoor), and the repeat was done in the same laboratory, with a bubble with a system that filtered large, medium and small particles, breathing the air outside the laboratory (outdoor). The parameters that were controlled were: the maximum power achieved on the ergometric bicycle expressed in watts (W), the ergospirometer parameters (VO 2max, VCO 2max, VE max), cardiological parameters: heart beats per minute and 2-hydroxypropanoic acid (La ++) levels and arterialised capillary blood glucose. Results The ergospirometer and cardiac parameters, or those associated with the power achieved on the ergometric bicycle did not change statistically, when we compared the two situations studied. However, the subjects did have higher levels of arterialised capillary lactate (+117%) 3 min after finishing the indoor situation test (7.55±1.81 vs 6.44±1.76 mMol/dl, P<0.016; n=13). We observed identical behaviour in the capillary blood glucose levels, which showed an increase of 112% in the usual situation (indoor) compared to those in the purified (outdoor) air bubble (blood glucose: 90.0±12.2 mg/dl vs 82.15±6.94 mg/dl; P>0.054 (not significant, n=13). Discussion The blood gas analysers for metabolic studies can be calibrated in different atmospheres and correctly determine the capacities and potential energy of these subjects, despite the atmospheric changes. The metabolic changes were sufficient to compensate for the different atmospheres compared, and enabled a similar level of physical performance to be expressed in the effort test and also in the cardiac behaviour during the same, considering the levels of contamination in a laboratory near Barcelona. Conclusions The subjects were able to adapt to the atmospheric changes owing to the gradual contamination. No differences were seen in the two situations established in the metabolic gas analyses under effort, and neither were there any changes in cardiac behaviour. The maximum potential obtained in the laboratory did not change. But, metabolically, a price was paid for atmospheric contamination, as shown by the higher mobilisation of glucose in capillary blood, and also in the higher production of capillary lactate under the conditions of the study.