A flame or gas detection method, comprising: determining a non-imaging sensor system detection state (16; 322, 336) for a scene of interest; determining an imaging sensor system detection state (18; 350, 362) for the scene of interest; validating one of the non-imaging sensor system detection state and the imaging sensor system detection state with the other of the non-imaging sensor system detection state and the imaging sensor system detection state; and indicating, at a user interface (124; 372), a flame or gas detection system detection state (26; 242, 244) including the validated one of the non-imaging sensor system detection state and the imaging sensor system detection state, wherein determining the imaging sensor system detection state (18; 350, 362) includes: receiving image data (24; 348, 360) from an imaging sensor (116; 338, 352) for the scene of interest; receiving imaging sensor system reference data (380, 388) for the scene of interest; receiving an imaging sensor system keep-out definition (382, 392) for the scene of interest, the keep-out definition demarcating image data frames of the image data into a frame region where flame indication is eligible for determining the flame or gas detection state and frame regions where flame indication is ineligible for determining the flame or gas detection state, the frame regions where flame indication is ineligible for determining the flame or gas detection state being unmonitored; and determining the imaging sensor system detection state based on the image data from the imaging sensor, the imaging sensor system reference data, and the imaging sensor system keep-out definition for the scene of interest. determining a non-imaging sensor system detection state (16; 322, 336) for a scene of interest; determining an imaging sensor system detection state (18; 350, 362) for the scene of interest; validating one of the non-imaging sensor system detection state and the imaging sensor system detection state with the other of the non-imaging sensor system detection state and the imaging sensor system detection state; and indicating, at a user interface (124; 372), a flame or gas detection system detection state (26; 242, 244) including the validated one of the non-imaging sensor system detection state and the imaging sensor system detection state, wherein determining the imaging sensor system detection state (18; 350, 362) includes: receiving image data (24; 348, 360) from an imaging sensor (116; 338, 352) for the scene of interest; receiving imaging sensor system reference data (380, 388) for the scene of interest; receiving an imaging sensor system keep-out definition (382, 392) for the scene of interest, the keep-out definition demarcating image data frames of the image data into a frame region where flame indication is eligible for determining the flame or gas detection state and frame regions where flame indication is ineligible for determining the flame or gas detection state, the frame regions where flame indication is ineligible for determining the flame or gas detection state being unmonitored; and determining the imaging sensor system detection state based on the image data from the imaging sensor, the imaging sensor system reference data, and the imaging sensor system keep-out definition for the scene of interest. receiving image data (24; 348, 360) from an imaging sensor (116; 338, 352) for the scene of interest; receiving imaging sensor system reference data (380, 388) for the scene of interest; receiving an imaging sensor system keep-out definition (382, 392) for the scene of interest, the keep-out definition demarcating image data frames of the image data into a frame region where flame indication is eligible for determining the flame or gas detection state and frame regions where flame indication is ineligible for determining the flame or gas detection state, the frame regions where flame indication is ineligible for determining the flame or gas detection state being unmonitored; and determining the imaging sensor system detection state based on the image data from the imaging sensor, the imaging sensor system reference data, and the imaging sensor system keep-out definition for the scene of interest.