None of the numerous referenced experiments carried out since the 1940s for the study of the characteristic ozone-induced cracking that occurs on the surface of rubber materials subjected to strain, are appropriate for the estimation of moderate to low ozone concentrations in air over 24-h periods. Given this situation, a methodology based on the image analysis technique has been developed, which allows daily ozone averages of less than 60 ppb to be differentiated. Given the simplicity and low cost of this technique, it is especially suitable for the control of the harmful presence of ozone over extensive woodland or areas of agricultural crops. The proposed method uses two formulations simultaneously on the basis of a single type of rubber, one with 0.5% of antiozonant and the other with 1%. The rubber samples used are shaped such that the stresses throughout them are not constant. The tests were performed inside a chamber in which different daily ozone evolutions, typical of those observed during the summer in rural areas of the central part of the Iberian peninsula, were simulated. The results obtained show a close relation between 24-h O 3 averages and the dimensional distribution of the cracks observed at different locations on the surface of the rubber samples. Also, in the case of typical daily unimodal ozone evolutions, there would appear to be a certain relationship between the maximum hourly concentration reached during the exposure period and certain crack characteristics.