Your fireplace operates by introducing the right combination of fuel, air and heat. After the fireplace is running, the next concern is efficiency. More specifically, how completely is the fuel burned and how much heat does the fireplace produce. This is broadly known as efficiency. From a mathematical standpoint, efficiency is calculated by dividing heat output by heat input.  Factors Affecting Efficiency  Efficiency is affected by temperature, turbulence, and time. These factors also impact heat transfer efficiency. Every substance has a minimum combustion efficiency needed for a fire to start and continue. High temperatures are essential to ensure {+}
Disclaimer: Diagnosis and repair should only be undertaken by qualified personnel.   As noted in previous posts, complete combustion of fuel requires a sufficient quantity of air. Without the right amount of oxygen, incomplete combustion will occur and produce a dangerous amount of carbon monoxide. The American National Standards Institute mandates that unvented gas heaters to be automatically turned off when the specified level of oxygen is not achieved. The automatic shut-off is controlled by the oxygen depletion sensor or ODS pilot system.   The ODS system is part of the pilot assembly designed to regulate the flame performance. The pilot flame is co {+}
During a combustion process hydrogen and carbon atoms of the gas come in contact with the oxygen atoms. Heat is introduced to the mixture increasing the molecular speed of the gas and oxygen molecules. The speed causes the molecules to collide with enough energy to break old bonds and create new ones. Molecules then release additional heat resulting in a self sustained combustion. New products produced are carbon dioxide (CO2) and water vapor (H2O).   Incomplete combustion is due to inadequate oxygen in the air to fuel mixture. This can be caused by one or all of the following  
  1. An inadequate primary air setting.
  2. Cooling of the flame by the flame c {+}