image of Combustion

How to look at a flame and know if it’s right


Looking at a flame and understanding what’s going on is more an art than a science.

There are however a few basic rules of thumb that can help you to know what’s going on. When you look at a flame you generally need to be looking at a flame moving towards you. It’s not a guarantee that you will even have a site port that will allow you to do this. If you find such a port, first wave your hand around it to make sure there’s no flue gas leakage. Then with a gloved hand, you push on the glass a little to make sure it does not break easily. Then with safety glasses on and a long-sleeved shirt, go ahead and look. You’ll be looking for a few basic things like:

combustion Colour


You’ll want to see a nice rich blue with a little orange or yellow tips. If you see a very pale blue, and if it’s noisy and appears to have a lot of energy and sharp edges, it’s probably too lean of a mixture. If the flame is fat, lazy and bright yellow or orange you’re way too rich.



The flames in a boiler should not be impinging on anything. They should be out into the open space. Likewise, it’s rare that equipment is designed for impingement onto walls or doors of an oven or furnace. The shape of the flame should be even and symmetrical



Things should look the same all the way around the burner and or down the length of the burner. There should be no glowing red spots where flames may be impinging on parts of the burner or dark spots where refractory has fallen out.


The flame should be evenly lit all the way around or down the length and this should remain for the entire range of operation. If the flame is pulled off of the burner face it’s called blow off. If the flame wants to crawl back into the burner it's called a flashback. These conditions are not healthy.

Combustion flame

Describing Burner Issues

When looking at a round burner try to superimpose the shape of a clock onto the burner and describe issues such as, (red sport at 2:00 o’clock). This is also a way to write notes in a log or journal that others can understand.

Signs of distress

Signs of distress

There are often exterior visual signs of burner problems like burned up paint on the outside of a unit and/or buckled plates. In some cases, if you look at a flue stack you might see evidence of shooting.

What to do

Burner flame problems can become severe in a hurry. Burners that are not adjusted properly waste fuel RANDS which no one can afford in today’s fuel price environment. The bigger problem is burners that are not adjusted properly or are impaired can lead to carbon fires and destruction of burner flame shaping diffusers which can lead to serious equipment damage. Fuel air ratios that are not correct can lead to accumulations of flammable mixtures that can lead to explosions. This has unfortunately happened on many occasions. If you have reason to believe that you have a burner issue give us a call. We might be able to review a MPEG video clip of it for you and give you some direction. We also have burner specialists on our staff who have expertise with many different types of equipment and styles of burners. Our staff has over 70 years of combined burner manufacturer experience.

Contact us today and allow us to build a solution for your business needs