Appts. for detection of underground fires - operates alarm when concentration of carbon dioxide sharply increases

摘要

Examinations of the air in mines and other underground works have proved that the carbon dioxide content sharply rises upon the outbreak of fire even while still containing a high percentage of oxygen. The carbon dioxide concentration increases faster than the carbon concentration. The invention applies this discovery. The apparatus continuously measures the carbon dioxide concentration of the space to be watched over. When the concentration exceeds a predetermined quantity an alarm signal is given. An analyzer of carbon dioxide in gas form is used as the detector. The electrical output corresponding to the level of carbon dioxide detected is increased by an amplifier and fed to a gauge to which a reference potential is connected. When the potential from the amplifier becomes greater than that of the reference potential an alarm signal is given, e.g. an alarm bell.