Fire from the outside in.

In the wake of the Chicago LODD last week (Herbert Johnson) there was a flurry of articles about flashover and attic fires.

All of these were great stuff and right on point. I wanted to take an opportunity while we were talking about these topics to talk about fires that start on the outside, climb and penetrate the building sheathing and wall covering and then we get the call.

There have been many circumstances where this type of situation has occurred, not the least of which was the Kyle Wilson incident.

My comments and thoughts below are not about any specific fire but just about these types of fires in general.

How do they start?

There are a variety of ways these fires can start. A gas grill fire that extends, grass and brush and mulch fires in contact with wood siding, careless disposal of smoking materials, external electrical (decorative lights cord) and many, many others.

In many if not all of the circumstances I will be referencing will be TYPE V wood frame construction.

Fire will generally enter an attic space through the small overhang of the roof line. This fire entering the soffit can rapidly find fuel (exposed wood Andorra attic storage) and rapidly spread. There is clearly an upward draft which exists and usually more than enough air to sustain free burning and fire growth.

There is generally little or no detection in uninhabitable attic spaces.

If occupants are home, they hear no alarms, see no smoke, and feel little or no heat . The fire continues to develop until it actually burns through or generates enough smoke that might be seen by a neighbor.

We arrive and have a well developed fire in a building void apace. Usually our best access (at least here in the northeast) will be a small 2 x 2 scuttle hole or attic hatch , with or without a ladder.

I have previously described and painted a pretty good picture of the conditions in the attic, now lets add some air from underneath. If the fire has free burned through the roof and venting well, things might be ok. If the fire has started to burn through but not quite, there is a tremendous amount of built up heat, products of combustion (read flammable gases) which might very well be forced down upon the scuttle opening with explosive force.

In addition certainly in wood frame construction there will be some drop fire down wooden petitions etc. balloon frame construction should be considered depending upon the age of the structure.

The bullet points or take aways from this quick post should be this:

Fires that spread from the outside in will generally have a pretty god head start.

After arrival of the FD we have a couple of tasks….search for life and search for the source of the fire. If interior companies are having trouble locating the source of the fire consider void space fires.

Exterior conditions might give the incident commander a better picture, because interior crews may not see and feel much from the inside.

Use EXTREME caution if you suspect lightweight roof construction. Consider the length of burning time and the fact these structural members are ready to fail.

Fire attack with simultaneous ventilation is always the solution to these problems, but more and more small suburban departments may not have the personnel immediately on scene to accomplish this. I am currently working on an article which discusses what we could do in the cases. Do I deploy all of my resources at the ventilation task while delaying attack, or do I start a cautious attack, knowing that my ability to advance might be limited, until ventilation occurs? (More on that later on)

Think about what we have discussed here today. Basement fires with extension, balloon frame construction issues etc, all present a similar circumstance, but when it comes from the outside in there are some different considerations.

Take a minute this week to review any case histories you know about, and talk its up around the kitchen table about any of these fires you might have responded Tao and operated at.

Stay safe!

Pete Lamb @ Copyright 2012
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