The discussion centers on the search for a material or chemical that visibly changes when exposed to THC, particularly for detecting marijuana smoke in a room. Various THC detection kits for saliva are available, but the challenge lies in airborne testing. It is suggested that if a room has a central air system, testing the particulates caught by the filter could be a viable method. The conversation also highlights that law enforcement uses specialized devices to detect trace amounts of drugs in the air, with dogs being a highly effective method for this purpose. Overall, while there are options for testing, a straightforward visible change in response to THC exposure remains elusive.