Size-up is defined in most fire service texts as the on going evaluation of problems confronted within a fire situation.

These strategic factors, listed above, are a good starting point to any size-up, but they could also be improved upon to give a more complete picture. For instance, are there energy efficient windows present in the building? Was the building constructed using new construction principles and materials? This may result in all or most of the products of combustion or indication fire of remaining inside the building. Is the wind blowing into the building making the interior untenable with no visible exterior signs of fire? Is smoke being observed or encountered in a location remote from or below the fire indicating additional fire or some kind of ventilation problem? What are the smoke conditions, how much and where?

There are five major areas of importance during a size-up where valuable information can be gained. They are:

  • Receipt of Alarm
  • En route Responding to the Alarm
  • Arrival at the Fire Scene
  • Inside the Fire Building or Area
  • Post Control Operations

In doing a size-up, the first thing to start with is the type of alarm received. Was it a phone call, automatic alarm, smoke detector, recorded device or pull box? If there is a phone alarm, for instance, a substantial amount of information can usually be gathered from the caller. "Fire is reported at 175 St. Johns Place, on the second floor", can tell us many things.

Most of the responding firefighters will have a general knowledge of the areas that they are assigned to protect. In this instance, many would know that the address given is in a residential area and even street numbers indicate that the address is on the north side of the street. Since the alarm was reported at 1:23 a.m., there is a strong possibility of sleeping occupants being victims of smoke and/or fire since most homes in that area have bedrooms on the second floor. While en route, the firefighters and officers should, if possible, be looking toward the direction of the reported fire for signs of smoke. This must be done with safety in mind, remembering that the members are on a responding apparatus and should remain seated and belted at all times.

Observing the vehicular traffic to ensure a safe response is still has the utmost importance. If smoke is observed, the members responding should note the amount of smoke (light, medium, heavy) and where it is coming from. (Window, chimney, roof, etc.) Often, even from a distance, there is an indication of the type of material burning, from its distinct odors. Wood, aluminum pots (food on the stove), rubbish, and plastics give off a unique odor while burning. Many veteran firefighters have learned to recognize and identify these burning materials through their sense of smell.

While approaching the fire location, special note should be taken of hydrant and/or drafting locations for a confirmed water supply. The front of the building should also be assessed for ladder use. Are aerial, tower, or portable operations indicated dictating placement of apparatus?

Upon arrival at the scene, the building should be sized-up before entering. The height, width and depth of the building should be noted, as well as, the location of visible fire and smoke. Means of egress and access such as fire escapes, porch roofs, portable ladders and set backs can be noted in case a need to retreat or evacuate occurs. Also, before entry, a 360-degree survey should be done of the exterior of the building and the results reported to all members on the scene. This will insure that no additional hazards are overlooked or go unreported to operating forces. An added benefit of this 360-degree survey allows for any victims who may need assistance or have jumped, prior to our arrival, to be located.

The type of construction and the condition of building can also be factored into a size-up. Is the building fireproof, wood framed or brick and joist construction? Will it limit or permit fire extension? Has the building been renovated to create concealed spaces or has additional living space been added, as in a separate apartment or private rooms (single room renters) in a private dwelling? Is the building under construction, thus limiting areas of refuge within the building or opening it to rapid-fire involvement throughout. The possible presence of holes in the floors and walls in buildings under construction also impact firefighting operations and should be included in the size-up.

The number of windows and their location should be carefully observed, as well as, if they appear to be discolored due to heat or smoke. Another thing to note before entering is the type of occupancy the structure is used for. Is it a single family home, a multiple dwelling, apartment house, commercial or business type of occupancy?