For better or worse, most of us know what fire looks like. It tends to look the same — orange-yellow colors licking their way upward — and it's a look we've come to expect.
At the same time, you've probably also noticed that some flames look different. This, of course, may have inspired a perfectly normal question: Why are some flames blue?
There's a perfectly understandable explanation for this. Read on for more!
Colors Come From Temperatures
Flames are different colors based on the temperature of the fire that you are looking at. For example, when you heat metal, you will see the color of that metal turn red, indicating that the metal is getting hot and ready to melt. When you burn something, such as a log or candle, you will see an orange or yellow color. You are not just looking at the color of the flame here, but you are also looking at pieces of soot starting to melt.
Hotter flames — such as the flames caused by gas — burn blue for many reasons. First, you are not just looking at wood burning but also at gas molecules. They burn blue as a result of the significantly higher temperature. Keep in mind that you are not actually watching gas "burning," per se. What you are seeing is hydrocarbon gas combusting. The gas ionizes, turning blue as it does so.
When It Comes To Gas Flames, Blue is Good!
If you aren't used to watching gas combust, you may be worried when you see a gas flame burn blue. Don't worry: This is a good thing.
A blue color when gas is burning indicates a properly burning flame. This means that the gas is burning at the color it was designed to. You may see a yellow tip of color at the top of the flame, indicating that the temperature is dropping as the flame glows higher. This is normal, although it does indicate that the flame may be burning at a less high temperature than you would expect it to do so.
If more than just the tip of your flame is orange or yellow, you are watching a fire burn at an incomplete combustion rate. This indicates a potential problem, and you should call a technician to address the issue. Yellow or orange flames with a gas burner mean that the flame is generating carbon monoxide. Turn the burner off right away, and call for professional assistance.
Blue Flame Means Safe Burning
When it comes to gas combustion, blue is good. It means that the gas is completely combusting, and no carbon monoxide is being generated. This means that the flame is safe. It is worth periodically inspecting any gas-burning device to check the color of its flame and make sure that it burns blue. This may not be the case for fireplaces, which are often treated with orange or yellow flames to have a more realistic look.
There you have it! Blue flames from gas result from the temperature at which the flames combust.