Mark Emery discusses why it's time for the contemporary fire service to adapt strategically and tactically. Why It's Time For the Contemporary Fire Service to Adapt Strategically and Tactically Characteristics of the structural fireground began to evolve 50 or 60 years ago. Collectively...
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An important distinction between a conventional beam and a lightweight truss is that the conventional beam is a single, solid, sawn piece of lumber; an open-web lightweight truss derives its strength from the triangular arrangement of a bunch of individual pieces that comprise the truss. Each of these pieces has a connection. It is important to understand that a truss is not a beam; although a truss is engineered to do the work of and replace a conventional beam, a truss does not deflect (bend) like a beam.
If you have 50 trusses and each truss contains 20 web members, you have exponentially increased the number of connections exposed to fire. No structural engineer is going to tell you that reducing the mass and increasing the number of connections will decrease the likelihood of failure should the assembly be exposed to fire. Exponentialize the number of connections and you exponentialize the likelihood of connection failure when exposed to fire. Visit your local truss manufacturer and ask a truss engineer: "Should a single panel point (connection) fail, what is the percent reduction of the safety factor?" You should not be surprised by the answer.
- Less time before failure - This one is easy: When you decrease the mass (less building) and increase reliance on tension (by eliminating compressive columns and bearing walls), and you exponentially increase the number of connections holding the lightweight assembly together, failure will - and does - occur much sooner on the contemporary fireground. Of course, there are ways to protect these lightweight systems (Sheetrock, sprinklers, etc.), but when unprotected and exposed to fire, it should be no surprise that the system will fail early. It should not come as a big surprise when a lightweight roof or floor fails "suddenly and without warning."
Effects of Encapsulation
Contemporary firefighters are festooned with a sophisticated protective ensemble that allows them to advance deep into a hazard environment. While this level of protection is remarkable, it fails to factor structural and environmental changes into which the firefighters advance - including zero visibility.
If you were around the fire service in the mid-1970s to early 1980s, you may have experienced the subtle philosophical shift when it became "important" for firefighters to have an intimate relationship with a fire within a building. For some reason, it became just as important to have firefighters mingle with the heat as it was to have water mingle with the heat.
We need to return to our traditional roots of ensuring that gpm mingles with Btu as quickly and efficiently as possible. So long as firefighters ensure that water does mingle with the heat, they do not need to be located where the actual mingling occurs. (A firefighter mingling with heat does not enhance Btu removal.) Remember: an intelligent and safe fireground operation is not about seeking opportunities for tactical entertainment; an intelligent and safe fireground operation is about seeking opportunities to achieve beneficial strategic outcomes - outcomes that include firefighters returning to quarters unharmed.
On the traditional fireground, it was common to flow between 125 and 150 gpm through handlines. Often, this flow was adequate to control a traditional fire load of 8,000 Btu per pound of stuff. Fast forward to the contemporary fireground. Due to the predominance of petrochemical-based fire load, the average Btu potential has doubled to 16,000 Btu per pound of stuff. It is remarkable that many fire departments upgraded from 1Â½-inch hose to 1Â¾-inch hose, yet still charge their handlines to 150 gpm - or less!
I'm not gifted with the mathematics gene, but if contemporary fireground Btu potential has doubled, it makes sense that gpm on the contemporary fireground be doubled. The recent emergence of low-pressure/high-flow nozzles is a positive step toward addressing this heat-removal inadequacy. My personal opinion: No hoseline on the contemporary offensive fireground should be charged to flow less than 200 gpm.
There are many gee-whiz nozzles that make this possible when attached to the business end of a 1Â¾-inch handline; a small handful are easy to handle as well. One example is the Vindicator Heavy Attack nozzle. Attached to a 1Â¾-inch handline and charged to 50 psi at nozzle pressure, you will be flowing 250 gpm. And here's the amazing feature: you can handle the hoseline with one hand - while standing, by yourself, without a hose strap. (This is not fantasy, I've done it.) Increase the nozzle pressure to 100 psi and you'll be flowing 425 gpm through your 1Â¾-inch hoseline!