Clean it using steel wool.
Blue flame is a clean flame.
A blue flame is call "clean" because it does not contain soot as a yellow flame does.
It tells the furnace that it lit... Hence the name Flame Sensor.
clean blue flame
A flame sensor is a program used to detect "flame" on various blogs or comment boxes. Various Websites may use these sensors to dish out trolls or other internet vermin. On the other hand a flame sensor is also a device used in machines that are subject to very high temperatures. For example, a flame sensor is standard in many home ovens. So this in fact is a very useful safty feature.l
clean blue flame
A flame sensor is a safety mechanism installed on gas furnaces. It is located directly between the burners and the gas supply. When your gas kicks on, the flame sensor MUST detect a flame. This safety mechanism is to prevent your house from filling up with un-lit gas. Even if your burners are igniting, if your Flame Sensor is dirty (covered in carbon from typical use) it will fault out, thus shutting off the furnace over and over. If this is the case, your furnace will kick on every 2 minutes (because the thermostat tells it your house is too cold) and then will shut off after 5 or 10 seconds as a result of the Flame Sensor Fault.
check your flame sensor
it is called a clean flame as it produces no soot and carbon minoxcide unlike the yellow/dirty flame.
The yellow flame (or luminous flame) should not be used because 1. It is less hot that the blue flame (or non-luminous flame) 2. It produces soot, as compared to the blue flame which is the clean flame
You can not successfully clean an oxygen sensor. You need to replace it.
Its not a flamesensor its a pilot generater it generates a small amound of electricity to open the main valve that way if your pilot light goes out it wont let gas escape and couse a potentian explosion The above answer is not accurate unless you have a standing pilot model furnace. Then the "flame sensor is called a thermocouple, much different than the flame sensors used in Direct Spark Ignition, hot-surface and intermitant ignition furnaces. The flame sensor uses the flame of the main burner to prove flame at the circuit board by measuring conductivity to ground through the flame.