Patent ID: 8917183

Claim:
An apparatus, comprising: a miner's helmet with a light mounted at a front side of the miner's helmet; a power source mounted to the miner's helmet that is electrically connected to the light; a gas sensor mounted to the miner's helmet that is electrically connected to the power source; a visual indicator mounted to a rear side of the miner's helmet; and electronics for changing the visual indicator in response to output from the gas sensor; wherein the gas sensor measures a concentration of a gas of interest and causes the visual indicator to display an alarm when the concentration of the gas of interest detected by the gas sensor triggers an alarm condition of the electronics; wherein the gas sensor is a non-dispersive infrared (“NDIR”) gas sensor comprised of: a single infrared source for generating infrared radiation into a sample chamber that is alternatively pulsed between a high temperature and a low temperature; a detector located in the sample chamber; a narrow band pass filter with a spectral characteristic that substantially overlaps a strong absorption band for the gas of interest located between the single infrared source and the detector; and electronics for determining a sample concentration of the gas of interest by use of an absorption bias between a signal output of the detector at the high temperature and a reference output of the detector at the low temperature; wherein a convoluted output of the single infrared source and the narrow band pass filter is substantially coincident with the strong absorption band at the high temperature.