Reading The Smoke

1. Reading The Smoke Fire House Weekly Drills

2. SMOKE! Introduction Smoke is present at EVERY fire! For some reason many new firefighters are fixated on running into the structures with little to no information. One thing that every firefighter should be doing is size-up. That smoke can be telling you something about the fire you are about to tackle. So, what does the smoke tell us?

3. SMOKE! Four Characteristics of Smoke There are four basic characteristics we can use to assist us in determining the size, location, and the effectiveness of the advancing hose team. Additionally, we should be able to apply smoke conditions to determine the potential for a flashover or backdraft.

4. SMOKE! What are the four characteristics? 1. Volume 2. Density 3. Velocity (pressure) 4. Color

5. SMOKE! First let's explore smoke for a minute. Smoke is the product of incomplete combustion resulting in a buildup of carbon, hydrogen cyanide, hydrogen sulfide, carbon monoxide, and an assortment of other extremely flammable gases. Smoke has a direct impact on fire behavior within the structure as we will learn.

6. SMOKE! A key to having a successful operation is that of performing ventilation properly. Proper ventilation will also curb the potential for a backdraft, flashover, and in most cases, eliminate some of the roll-over fire conditions experienced on the inside by the hose team.

7. SMOKE! Volume Volume will really tells us very little about the fire conditions within the structure but it benefits us by giving some indication as to the amount of fuel that is being consumed and producing this incomplete combustion. A free burning fire, which has sufficient oxygen, will produce very little if any smoke, due to the complete combustion being allowed by the supply of oxygen and ventilation.

8. SMOKE! Volume On the other hand, a fire with limited or poor ventilation and having a minimum supply of oxygen begins to produce smoke as a direct result of incomplete combustion which is occurring. A fire that is developing and spreading quickly will produce a tremendous volume of smoke.

9. SMOKE! Density Density can be thought of as the thickness of the smoke and is a good indicator of incomplete combustion. Remember, this is also a sign of poor ventilation which causes the fire to consume the oxygen in the immediate area around the fire. This lack of oxygen slows the burning process and produces smoke. Smoke that is showing a very dense makeup is saturated with highly flammable gases just waiting for the proper fuel/air mixture to ignite. Sometimes this occurs violently!

10. SMOKE! Density Many of the items found in homes and offices today are made of synthetic materials or plastic. These materials generate a large quantity of dense smoke, even at relatively low temperatures. Even at these lower temperatures the smoke produced can be very explosive. Generally, trapped victims will not survive a fire that has severely dense smoke condition.

11. SMOKE! Velocity Velocity is caused by pressure building up within the involved structure. Another way to look at velocity is to think of it as the rate at which the smoke is moving. During a fire, pressure begins to build from the heat being produced and the volume of smoke filling the area. In addition the lack of, or limited ventilation effects the smoke's production due to the incomplete combustion which is occurring.

12. SMOKE! Velocity This build up of pressure has a direct bearing on the smoke and begins to push it out of the structure via openings in the exterior walls, including windows, doors or other openings in the structure. So which is it, the heat or the smoke causing the velocity issue?

13. SMOKE! Velocity Should the smoke's velocity have the appearance that it is boiling out the openings, keep a close watch on it. This is a tell-tale sign that flashover is imminent. Begin ventilation before moving in with a charged hoseline and move slowly and cautiously. Velocity can also provide an indication of the fire's location. Smoke exiting from the structure, having a strong velocity appearance is an indication that the heat source is nearby.

14. SMOKE! Color Color is a very important component and can give us a good indication of the stage that the fire is at. White smoke indicates the fire is in the incipient stage and conditions are generally tenable. It can also indicate when interior crews are successfully applying water to the fire. As the fire progresses to the next stage, wooden materials begin to break down because of burning and produce a tan or light brown smoke.

15. SMOKE! Color As the smoke becomes browner in color, we need to be thinking that it has reached the structural components (studs, rafters, joists, etc.) of the building. With today�s lightweight construction features this may imply imminent collapse.

16. SMOKE! Color Plastic materials will produce a gray color smoke in the early stages, but most of the time it is black smoke. The blacker the smoke, the more indication there is of it containing carbon, hydrocarbons, and flammable byproducts.

17. SMOKE! Keeping in mind the principles learned with velocity and density, one could conclude that a higher the velocity and a lower the density, smoke conditions are being pushed by a relatively free burning fire. One could also conclude that a lower velocity and high density smoke can mean that a fire is venilation starved.