Oxygen Depletion System is called ODS for short, When gas appliance is working in a unvented space for some time, the oxygen is involved in chemical reaction and produced water vapor and carbon dioxide during combustion. In this case, the oxygen content in this unvented space is decreasing while carbon dioxide content is increasing. People will feel uncomfortable when oxygen content arrives the level 16%-17% or higher. It will even cause toxicosis when carbon dioxide content arrives the level 4% or higher.
While Oxygen Depletion System can above dangers and promise safe operation in unvented space. It will cut off the energy source so that gas appliance stop working to assure personal safety once oxygen content arrives the level 18.5%-19.5% and carbon dioxide content arrives the level 0.8%-1.5%.