Understanding Fire Behavior: Why Are There No Flames in the Smoke, Even Though There is More Oxygen?

Report Date: July 2015

Typical modern structural fires encountered by firefighters are generally ventilation limited. As oxygen in the structure is depleted, the flames and temperatures decrease. After the initial drop in oxygen, oxygen levels begin to increase, but there is no corresponding increase in temperature or flames. Why is this?

Firefighters need to truly understand fire phenomena in order to select the proper tactics and anticipate dangerous conditions. To do so, they must first have a basic understanding of the physics of fire behavior. This is another video by Battalion Chief Ågerstrand in Sweden that further explains some of the basics of fire behavior and the concepts of a thermal ballast, flammability limits, and backdrafts. The video introduces some great fire science visualization tools that can be used to help understand fire behavior.


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  • Swedish Firenerd

    My ambition has always been to move forward, always continue to develop and improve. I seek new questions where there are none and challenge what it is held as truth. My foremost goal is to inspire firefighters to learn, to make them students of their trade.

    When the will to learn is there, all I have to do is to point them in the right direction, as so many have done for me. The practice of firefighting is a life-long learning endeavor where absolute truths are scarce and logical fallacies fill the gaps in our knowledge. Being a student of firefighting means being open to change. Our new experiences combined with an influx of science helps us to let old beliefs die.

Ågerstrand, Lars. Why are there no flames in the smoke, even though there is more oxygen? Online video clip. YouTube, 28 July 2015. Accessed from https://youtu.be/S0Gs2wYigLk on 02 August 2015.

Image Credit: http://www.chicagofirewire.com/
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