Apparatus and associated methods relate to a gas detection apparatus including a main optical element configured to: (1) direct a first portion of light emitted from a light generating element (after the first portion of light has interacted with a target medium) to a primary detector via a second optical element, and (2) direct a second portion of light emitted from the light generating element to a reference detector via a third optical element. In various examples, the main optical element may be a reflector such as a mirror. The light generating element may, for example, be a red, green, and blue (RGB) light emitting diode(s) (LED(s)). The optical train may, for example, have a single/unitary molded transparent acrylic construction and internal reflective surfaces. A gas detection apparatus may standardize the optical path used by the light generating element and the primary/reference detectors, advantageously providing for reliable operation.
