It consists of a light source, detector, and tube smoke purge system. The purpose of the transmissometer is to accurately measure the smoke generated, assuring that the applicants are correctly trained and tested. Calibration is performed using NIST certified optical filters. The output from the transmissometer is recorded on a strip chart recorder. An induced draft fan blows the generated smoke past the transmissometer an out through the top of the stack.
White smoke is generated by vaporizing diesel fuel in a specially designed system .
The vapor is diluted with ambient air to form a mist. The mist is conveyed to the fan and out the stack passing the transmissometer. Black smoke is generated by burning organic hydrocarbons in a specially designed firebox. Poor combustion is encouraged creating soot. The soot is conveyed to the fan and out the stack passing the transmissometer.