A self-timing, passive, chemical dosimeter. The dosimeter includes a sampling media and electronics supported by a cassette. The sampling media is configured to absorb volatile organic compounds, semivolatile organic compounds, or both, while the electronics are configured to record a time of exposure. The dosimeter further includes an actuator having a closed position and an open position. In the closed position, the actuator resists exposure of the sampling media to volatile organic compounds, semivolatile organic compounds, or both, and in the open position, the actuator permits exposure of the sampling media to volatile organic compounds, semivolatile organic compounds, or both. The actuator is configured to operate the electronics for recording time of exposure.