Ortho-chlorobenzylidene malononitrile (CS) "tear gas" is a lacrimating riot control agent causing eye irritation, excessive lacrimation, and blepharospasm. Diphoterine has been efficacious for decontamination of a wide variety of eye and skin chemical splashes and was tested in CS exposure. Five French Gendarmes either entered a standard training CS exposure chamber, developed eye or skin signs and symptoms, and were post-exposure decontaminated with Diphoterine or used Diphoterine as pre-CS exposure prophylaxis in the eyes and on the face before entering the chamber. Gendarmes who entered the CS chamber without prior application of Diphoterine developed expected effects of excessive lacrimation, eye irritation, and blepharospasm. After post-exposure Diphoterine decontamination, in four Gendarmes these effects rapidly resolved and they were fully operational. When Diphoterine was applied to the eyes and face before entering the CS chamber, the expected effects did not occur and the single Gendarme remained fully operational on exiting the chamber. These results suggest that Diphoterine can prevent or rapidly ameliorate the ocular and dermal effects of CS and allow law enforcement personnel to remain fully operational or rapidly regain operational status after decontamination.