Chemical substances such us CS-gas used in military operations are chemical compounds that present a series of peculiarities that affect the ecosystem by disrupting the ecological balance. This study evaluated the toxicological character of O-chlorobenzylidenemalonitrile (CBM), (substance present in CS-gas) on the algae Cholrella sp. and analyzed the toxicity limit and the response of the microorganism to the oxidative stress caused by this substance. In order to under-stand the toxicological mechanisms of CBM on algal culture, a series of parameters were analyzed such as: the cell growth curve, the average specific growth rate (µ), percent inhibition in yield(I%), dry cell weight (DCW), percent viability and productivity of algal biomass flocculation activity(FA), change in oxygen production. The content of chlorophyll pigments, was characterized by Fourier transform infrared spectroscopy (FTIR) fluorescence spectroscopy and analysis of the surface structure of algal cells by SEM spectroscopy. This study aims to provide fundamental data for understanding the toxicity of CBM to aquatic organisms and provides a basis for assessing the potential for impact on aquatic ecosystems. The results obtained could be taken into account in the management of the decontamination of the affected areas.