Abstract: A device is provided which passes light of preselected wavelengths through a fluid, gas or vapor to be tested. The light is detected after it has passed through the fluid, gas or vapor. Upon detection, a voltage is created which is proportional in amplitude to the detected light strength for each wavelength of light. These voltages are compared to produce a ratio which represents the condition of the fluid, gas or vapor which is tested or the presence of an analyte of interest. When the ratio is outside of preselected boundaries, control signals are generated which may trigger alarms or otherwise respond to the condition. In a preferred embodiment of the invention, the presence of carbon gases such as carbon monoxide and carbon dioxide is detected in gases or vapors.

Abstract: A device is provided which passes light of preselected wavelengths through a fluid or vapor to be tested. The light is detected after it has passed through the fluid or vapor. Upon detection, a voltage is created which is proportional in amplitude to the detected light strength for each wavelength of light. These voltages are compared to produce a ratio which represents the condition of the fluid or vapor which is tested. When the ratio is outside of preselected boundaries, control signals are generated which may trigger alarms or otherwise respond to the condition.