How To Do A Proper Size-Up As First-Due Officer (Framework + Common Failures)

Size-up is not a one-time event when you pull up. It is a continuous discipline that starts at dispatch and does not stop until the last hose is loaded. The first-due officer who treats size-up as a single transmission on arrival is going to make tactical decisions on stale information. The officer who treats size-up as a running internal narrative, updated every 30 seconds, is the one who catches the partial collapse warning, the wind shift, the second exposure, the missing occupant car.

The hard part of size-up is not learning the acronym. Every probie can recite COAL WAS WEALTH or some version of it. The hard part is doing the acronym while you are also stepping off the rig, putting on your pack, reading the smoke, and getting ready to give a coherent on-scene report that the second-due crew and the BC can actually act on. Under that kind of load, the framework collapses unless you have practiced it cold.

The good news is that size-up is one of the most trainable skills in the fire service. It is repeatable, it has a clear right and wrong, and the patterns show up across every occupancy. Once you have run two hundred mental reps on residential fires, you can read a structure from the cab in about eight seconds. The framework below is the one that holds up across the standard references (Norman, Dunn, IFSTA), and it is the same framework that the AI-graded sim on StruckBox scores against.

The first inputs to your size-up are the dispatch comments, the time of day, the address, and the weather. By the time the wheels are turning, you should already have a working hypothesis about what you are rolling to.

Time of day matters because it predicts occupant load. A residential fire at 0300 is presumed occupied with people asleep. The same fire at 1430 on a Tuesday is presumed unoccupied or partially occupied with kids and a caregiver. Your search priority shifts accordingly. Commercial fires invert. A strip mall at 0200 should be empty. A strip mall at noon has employees, customers, and deliveries.

Address tells you occupancy type, neighborhood construction era, and any pre-plan history. If your department keeps target hazards updated, the dispatch screen should be cueing you. Wood-frame post-war ranch versus 1920s balloon frame versus modern lightweight truss residential are three completely different fires. Your tactics need to know which one before you put a foot on the ground.

Weather is the input most officers underweight. Wind speed and direction control flow path. A 25 mph sustained wind through a failed window can push fire through a single-family residence in under 90 seconds. UL-FSRI's wind-driven fire research is the body of work every company officer should be familiar with. Cold temperatures slow water flow and stiffen hose. Heat and humidity tank crew endurance. None of this changes the strategy, but it changes the tempo and the rotation plan.

If you cannot complete a 360, you cannot do a proper size-up. Period. This is the single most violated rule in the American fire service and it shows up in NIOSH LODD reports year after year. A 360 reveals the basement fire that was not visible from Side A, the failed exposure on the Charlie side, the propane tank, the open back door, the occupant on the second floor balcony, the wind direction relative to the fire, the smoke conditions on the unburned side.

If geography or attached structures make a full 360 impossible, you assign one. You send the second-due officer or a designated firefighter around the building and you wait for that report before you commit your attack. "Held 270, Charlie side reported by second-due" is a legitimate transmission. "Made entry without a 360 because we had a job to do" is the kind of decision that ends up in a case study.

What you are looking for on the 360, in order of priority: any sign of life (occupants at windows, vehicles in driveways, pets, toys, accessibility ramps). Smoke and fire conditions on all four sides. Grade changes that reveal a walkout basement. Exposures (other structures, vehicles, propane, utilities). Forcible entry conditions on the unburned side. Wind direction relative to fire location. Anything that contradicts the dispatch information.

There are three size-up frameworks in common use and they each have a role. The mistake is trying to recite one while running an incident. The frameworks are for training and review. On the fireground, you internalize them and produce decisions.

COAL WAS WEALTH (Construction, Occupancy, Apparatus, Life, Water, Auxiliary appliances, Street conditions, Weather, Exposures, Area, Location, Time, Height) is a comprehensive checklist. It is the gold standard for written exams and oral boards. It is too long to run in your head on a working fire. Use it for pre-planning and after action review.

RECEO-VS (Rescue, Exposures, Confinement, Extinguishment, Overhaul, Ventilation, Salvage) is a priority order, not a checklist. It tells you what to do, in what order, on a structure fire. This is the framework you actually run live. Life safety first, exposures second, confine the fire third, extinguish, then overhaul. Ventilation and salvage are timing-dependent and slot in where they fit.

SLICERS (Size-up, Locate, Identify, Cool, Extinguish, Rescue, Salvage) reflects UL-FSRI's research that cooling the fire from a safe location early can save lives by reducing the heat release rate before interior crews commit. It is not a replacement for RECEO-VS. It is a refinement for situations where a transitional attack is justified by the fire conditions.

The senior officer's move is to know all three and pick the right one for the situation. Light smoke from an unconfined room and contents fire, RECEO-VS works fine. Wind-driven, fully-involved fire on Side A with crews still pulling lines, SLICERS justifies a 15-second exterior hit before transition. Big-box commercial with delayed alarm, COAL WAS WEALTH on the way in because you have time and your tactics need to match construction.

Smoke reading is the single most underrated skill in size-up. Dave Dodson's framework on smoke (volume, velocity, density, color) is the standard reference and every company officer should be able to apply it cold.

Volume tells you fire size. A puff at the eaves is a different problem than smoke pumping from every soffit. Velocity tells you pressure inside the structure, which correlates with fire intensity and ventilation status. Smoke moving slow and lazy means low pressure differential. Smoke pushing hard and turbulent means high pressure, high temperature, and a structure that is approaching a critical event.

Density is the part most officers miss. Thick, optically dense smoke is loaded with unburned fuel. It is a flashover indicator. When the smoke in the room is the fuel, you are inside a fuel-air mixture waiting for ignition. The textbook indicator is smoke that looks like it should be solid. If your crew is hitting that condition in a corridor, you need to cool the gases overhead and consider whether you are in the right position.

Color tells you what is burning and how completely. Brown smoke from a structural area suggests pyrolysis of structural wood, which is a collapse warning sign. Black, oily smoke suggests synthetics burning rich with insufficient oxygen, which is a flashover warning. Light gray to white can mean steam (water on fire), moisture from new fuel, or smoldering. Reading color without volume and velocity context will fool you. Read all four together.

The mental rep here is to watch every video, every drill, every working fire you respond to and call your smoke read out loud before the truth reveals itself. Over time you build a library of patterns. That library is what lets you predict flashover, collapse, and flow path before they happen.

Tunnel vision on Side A. The fire is what you see and what you see is what you treat. The 360 is the cure. If you skip it, you will keep skipping it until it catches you on the kind of fire that ends up in a NIOSH report.

Committing crews before the size-up is complete. The on-scene report and the strategy declaration should come before the attack line goes through the door, not after. Even 30 seconds of pause for a coherent size-up will save you minutes of bad tactics. The classic version of this failure is the officer who jumps off the rig, grabs an irons, and ends up not at the command post and not at the size-up position, but somewhere in between with no radio discipline.

Failing to communicate the strategy. Strategy is binary. Offensive or defensive. Investigative is a transitional posture, not a strategy. Your second-due units need to know which one you have declared. "We have a working fire, offensive strategy, primary search Side A through Charlie, second-due to Side Charlie for a 360 confirm and water supply." That kind of transmission gives everyone the picture.

Anchoring on the dispatch information. The address is the address but the picture on arrival is the truth. If dispatch said "smoke from the back" and you see fire from the second floor on Side A, your size-up is what you see, not what you were told. Update the picture out loud.

Treating modern construction like legacy construction. Lightweight engineered lumber fails fast under fire load. Truss roofs collapse without warning. NFPA's residential fire ground research and UL's collapse timing studies are clear that you have less time on modern construction than the textbooks from the 1990s reflect. Your size-up has to read construction type and adjust your interior commitment timeline accordingly. Brannigan's rule still holds: the building is your enemy, know it before you fight in it.

Skipping the time check. Elapsed time on the fireground is a primary input to your strategy decision. NFPA 1700 (Standard for Structural Fire Fighting Operations) and the modern command literature reflect the fact that fires in modern fuel loads transition from contents to structural involvement faster than they used to. A 20-minute mark on an offensive interior attack should trigger a check on progress and a deliberate go/no-go on continuing offensive operations. Most departments do not enforce this. The ones that do, do not lose firefighters in collapse.

Reading articles on size-up is the warm-up. The skill is built through repetitions where you make a call, get feedback, and adjust. Drill ground reps with smoke generators are excellent for crew coordination. Tabletop drills with photographs of working fires are excellent for the pure size-up read.

The hardest reps to come by are the ones where you actually have to compose a size-up out loud, under time pressure, with smoke conditions changing, and get graded on whether you covered the inputs that mattered. That used to require a captain or chief willing to sit across from you with a stopwatch.

StruckBox includes a free tactical fire sim that puts you on Side Alpha of a real-looking structure fire (smoke and flame visible from the photograph), asks you for your size-up, and grades your transmission on the inputs a panel or a deputy chief would actually score: smoke read, construction call, life hazard, strategy declaration, exposures, water supply, command structure. You get a written breakdown of what you covered and what you missed. Run it three times a week for a month and your size-up vocabulary gets sharp the same way oral board prep does, through high-volume reps with feedback.

The first-due officer who consistently runs a clean size-up is not the one with the best memory for acronyms. It is the one who has done the most reps. Get the reps in cold, in your kitchen, on your phone, when nothing is on fire. Then when something is on fire and the crew is looking at you for a picture, the picture comes out clean.