A hazardous material detection system (104, 202) for detecting occurrence of a hazardous condition event based on subject behaviors indicators, comprising: a surveillance system configured to monitor subjects within an environment to generate monitoring data, wherein the surveillance system comprises of both a visual surveillance system (106, 302) and an audio surveillance system (107, 304), wherein the monitoring data include imaging data and audio data, wherein the audio surveillance system comprises at least one of an acoustic transducer or a microphone and the audio surveillance system is configured to record audio data of sounds, noises, and audible expressions of the subjects; a detector (109, 215) configured to analyze the imaging data and the audio data to detect indicator instances that indicates that a release of a hazardous material occurred, wherein each of the detected indicator instances is an instance of a corresponding event indicator in a set of pre-selected event indicators, wherein the pre-selected event indicators are indicators established as known reactions or responses of the subjects to the release of a hazardous material; and an analyzer (111, 216) configured to evaluate the indicator instances identified to determine whether the indicator instances meets an event detection threshold, thereby indicating a detection of the hazardous condition event within the surveilled area and triggering an alarm system, wherein the hazardous condition event is a presence of a hazardous material in a location relative to the environment and wherein the subjects exhibit the indicator instances in response to exposure to the hazardous material. a surveillance system configured to monitor subjects within an environment to generate monitoring data, wherein the surveillance system comprises of both a visual surveillance system (106, 302) and an audio surveillance system (107, 304), wherein the monitoring data include imaging data and audio data, wherein the audio surveillance system comprises at least one of an acoustic transducer or a microphone and the audio surveillance system is configured to record audio data of sounds, noises, and audible expressions of the subjects; a detector (109, 215) configured to analyze the imaging data and the audio data to detect indicator instances that indicates that a release of a hazardous material occurred, wherein each of the detected indicator instances is an instance of a corresponding event indicator in a set of pre-selected event indicators, wherein the pre-selected event indicators are indicators established as known reactions or responses of the subjects to the release of a hazardous material; and an analyzer (111, 216) configured to evaluate the indicator instances identified to determine whether the indicator instances meets an event detection threshold, thereby indicating a detection of the hazardous condition event within the surveilled area and triggering an alarm system, wherein the hazardous condition event is a presence of a hazardous material in a location relative to the environment and wherein the subjects exhibit the indicator instances in response to exposure to the hazardous material.