A Flows Path

Ray McCormack

When we open the entry door, we’ve been told to think of that as ventilation, and the effects of that action as negative. The fire service should never think of entry in a negative context. We should think about entry as creating flow. 


Flow is more than just air going to a fire or moving away from it. Flow gives us the opportunity to evaluate conditions on the inside once the door opens. Interpreting flow direction and function from this location provides an opportunity to determine if we are in a shared or single directional space.
Is the opening providing a bi-directional flow? Bi-directional flow Is low-air entry and high-level exhaust within the same opening. Is the opening displaying a uni-directional flow? Uni-directional flow is an opening where a single direction flow is prominent. A location with a uni-directional flow can function as an inlet flow or an exhaust flow.


Is the open entry door a ventilation point? Of course it is, but it’s more than that. It’s an information portal. When you open the entry door, heat and smoke will escape and fresh air will also track in low. This new flow will find its way to the fire. The route it takes is the flow path. It may return to you or exit in another area depending on its function. Understanding directional flow tells our people a lot more than simply saying something is ventilation.


Opening the entry door is required for us to size up the fire, enter and provide extinguishment. When we open the entry door, we can also close it. When you remove glass, we can’t control that opening any longer; however, doors are different, we can control doors there by controlling flow.

Firefighters know that air will feed the fire, and that fresh air will track inside low to the ground. That entry air can be beneficial to someone lying on the floor in the path to the fire – the flows path. Flow is what we’re interested in understanding, flow towards the fire and away from the fire. If you were to enter through the doorway and close the door behind you, you have eliminated that flow. 

By discussing the term Flow, we bring understanding to the movement of air, gases and fire. Firefighters need to understand that the creation of flow is not a negative, and the controlling power they have over flow. While we can’t always control flow we must consider it’s path as we operate and avoid being in an active exhaust flow. There shouldn’t be negative connotations to opening an entry door. There should be understanding of actions and the impact of those actions, so that recognition is more universal.

3 thoughts on “A Flows Path

  1. Excellent job explaining the importance of observing the direction and speed of the flow. Whether it’s the inflow of fresh air, the outflow of the products of combustion or bidirectional flow, the flow gives us clues as to what’s going on in the building and helps with our decision making, ie: Should we be making our attack or search from this location? Is this the exhaust flow and we are entering in a tenuous position? Is the air rushing in fast indicating that you maybe entering a severely vent limited environment that’s looking to escalate rapidly and dangerously with this inrush of air? Do you observe bidirectional flow that maybe providing relieve to a trapped occupant?
    All important observations that provides clues that we should be training our firefighters recognize and access when opening the front door!

    As always, Stay Safe!

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  2. A common term from years ago was upon entry into a burning apartment was “Let it Blow”
    This meant the locked or closed door was keeping the heat and smoke in and when the Truck forced entry, the door was opened, but kept In Control with a tool to let the pent up heat and smoke roll out and “lift” from the floor.Flow Path in and out just as Ray described.
    This would allow three things:
    A clearer view of the apartment “Lay Out’ such as a straight in with rooms on the left, right or a apartment which runs in two or three directions.
    The location of the fire might be seen and the Engine would make their move in the correct direction.
    Also a Fireman “Staying Low” has a better chance with some visibility to find a victim on the floor especially near the normal entrance/exit to the apartment. This was especially important before the TIC was in common use.
    The location and extent of the fire, as well as the hose line status such as:
    Line charged and in position.
    Line is still being stretched.
    Engine is Delayed etc.

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  3. Great remarks by Lt. McCormack and those who have commented ahead of me. I’ll just add a few thoughts. I remember as a young fireman being taught to observe the “4 L’s” when I got to a door, especially the door to the fire room but it applies to the front door too: Life (look for victims), Layout (of the room), Lift (read the smoke – mostly its turbulence and the level of it relative to the ceiling/floor), Location (of the fire … sometimes the open front door allows you to find the fire in heavy smoke when it lights off with the introduction of air). All of this was to happen with the door controlled and with water at the nozzle but before the nozzle was opened. The TIC is a great tool today to assist with analyzing these “4 L’s”. Open the door – Read the door – Control the door – Bring water with you – Constantly monitor conditions, especially overhead/cool as needed. Getting water on the fire is a great #1 tactical priority, allowing the searches to get done. I was never big on closing the door behind the advancing nozzle team but I understand the concept. In my experience we always got to the fire with a charged hoseline before the open door behind us posed a problem. I know that some Departments, if staffing allows, use a door control firefighter behind the nozzle team to partially close the door and at the same time monitor conditions. Opening the door is ventilation, but a well trained crew can take advantage of what the open door gives them and is aware of what its consequences are and how to handle them.

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