PILOT BURNER B880205

When a vent-free gas product is operating in a room with a normal oxygen level (i.e., 20.9 percent), the pilot flame of the ODS system is in contact with the ODS thermocouple that generates the necessary millivoltage needed to hold the solenoid safety valve inside of the control valve in the open position. The ODS safety valve is a "Spring-Loaded Normally Closed" valve.In the event the oxygen level in the surrounding atmosphere begins to drop to approximately 19 percent, the pilot flame at the precision "ODS" burner begins to lift-off the ODS thermocouple. The thermocouple begins to cool. Before the oxygen level in the surrounding atmosphere drops to 18.5 to 18 percent, the unstable pilot flame moves away from the thermocouple causing the thermocouple to cool to a point where the millivoltage needed to hold the safety valve open is no longer generated. The safety valve closes causing the gas supply to the vent-free gas product to be cut off. The appliance shuts down. It is important to understand that the ODS system does not sense carbon monoxide directly, it responds to a reduction of oxygen in the area of the appliance.The 18 percent oxygen cutoff level was selected based on a National Bureau of Standards (report that illustrated the emissions from vent-free gas products would remain relatively stable through an operating range of normal oxygen level to an 18 percent oxygen level. However, once the oxygen level drops significantly below 18 percent, appliance emissions are drastically altered and carbon monoxide can be produced at an exponential rate. As noted before, the Consumer Product Safety Commission has recognized the ODS system as an effective way to address the risk of carbon monoxide poisoning, and the safety record of ODS equipped vent-free gas products have proven them right.