Reading Smoke: A Three-Step Size-Up

By COLE KLEINWOLTERINK

In December 2024 and January 2025, we examined the four attributes of smoke: velocity, volume, density, and color. Understanding each attribute is important, but firefighters must also know how to combine those observations into a quick, repeatable size-up.

When reading smoke, I have found the greatest success using the threestep process I learned from Captain Rob Backer in his class, The Art of Reading Smoke. The process is fast, practical, and repeatable, giving firefighters a consistent framework for organizing what they see instead of relying on a single smoke attribute or first impression. With practice, it helps crews move from simply observing smoke to interpreting what it reveals about the fire’s location, intensity, direction of travel, and rate of change.

STEP 1: INVENTORY THE SMOKE Begin with a complete scan of the building. Identify every location where smoke is visible, note areas where it is unexpectedly absent, and evaluate the number and size of the openings through which it can escape.

Do not become so focused on visible flames that you fail to examine the rest of the building. Flames attract attention, but smoke from windows, doors, eaves, roof openings, vents, seams, and utility penetrations provide a more complete picture of what is happening inside.

Avoid describing the entire building as simply having “light smoke” or “heavy smoke.” Instead, evaluate the four smoke attributes (volume, velocity, density and color) at each opening.

STEP 2: IDENTIFY WHAT IS INFLUENCING THE SMOKE Account for outside factors that may distort what you see. Begin with the building itself, then consider how current weather conditions may be affecting the smoke’s movement and appearance.

Consider the building’s size, construction, layout, contents, and ventilation openings. Smoke conditions that appear significant in a small bedroom may look less dramatic in a warehouse, even when the warehouse fire is producing considerably more smoke simply because the container is much larger.

The building can also filter and redirect smoke. Hallways, closed doors, stored contents, wall cavities, floor systems, and attics create resistance, which may slow the smoke, lighten its color, or cause it to appear far from the actual fire. Opening size also affects velocity. A small opening may create a concentrated, high-velocity stream, while a larger opening allows pressure to escape with less visible speed. For that reason, it’s best to compare smoke coming from similar sized openings when possible. The second influence is weather.

Wind may push smoke back into the building, increase its velocity on one side, or hide conditions on another. Cold air can cause smoke servation made on arrival. Conditions must be reassessed throughout the incident, especially after firefighters open doors, break windows, begin ventilation, or apply water. to fall and remain near the ground. Humidity may keep smoke together in a defined column, while dry air may allow it to disperse more quickly. In freezing conditions, the smoke’s appearance may change almost immediately after it reaches the exterior air. Condensation can lighten its visible color, so firefighters should evaluate what is occurring at the opening rather than relying only on the color seen farther away.

STEP 3: DETERMINE THE RATE OF CHANGE Reading smoke is not a single observation made on arrival. Conditions must be reassessed throughout the incident, especially after firefighters open doors, break windows, begin ventilation, or apply water.

Continually evaluate whether the smoke is increasing or decreasing, whether laminar flow is becoming turbulent or turbulent flow is becoming laminar, whether the smoke is growing darker or denser, and how quickly those changes are occurring.

Continually size-up the smoke profile throughout the incident. Changes in visible fire may be misleading when smoke, heat, and pressure continue to build. Flames may disappear when a fire becomes ventilation-limited, while heat and unburned fuel continue accumulating inside. Less visible fire does not always mean conditions are improving.

Consider a two-story residence with dense, turbulent black smoke with bi-directional flow pushing from a first-floor window and dirty white smoke exhausting from the entire opening of the second floor window. Over several seconds, the upstairs smoke becomes darker, denser, and faster. Conditions on the first floor suggest that the main body of fire is nearby. The lighter appearance upstairs should not be mistaken for cooler or less dangerous smoke; its characteristics may have changed as it moved through the structure. The worsening conditions described on the second floor indicate that the fire is intensifying below and extending upward. Without timely water application, fire involvement on the second floor is likely.

The three step process should leave firefighters with an operational picture: where conditions are most severe, which areas are being threatened, whether the problem is expanding, and how urgently tactics must be applied.

MONTHLY DRILL Find several structure-fire arrival videos and pause each one shortly after the building becomes visible. Have each firefighter verbally go through steps 1 and 2 by identifying the likely fire location, the direction it’s likely to travel, the conditions affecting the smoke, and the potential for a hostile fire event at that moment. Then continue playing the video and complete step 3 by evaluating how conditions change over the next 30 to 60 seconds.

The more often crews practice this process, the faster and more accurately they will be able to apply it during an actual size-up.

Cole Kleinwolterink is a member of the Waukee Fire Department, Van Meter Fire Department, and Fire Science instructor at Des Moines Area Community College. Feel free to reach out to him atkleinwolterinkc@gmail.com with any questions, comments or inquiries.