FireRescue magazine's Fireground Operations Web column
Take Heed:What you need to know about truss construction to avoid making mistakes & causing injury
By Freddie LaFemina

In years past, the mantra of “putting the fire out no matter what the cost” resulted in the deaths and serious injuries of many firefighters. Sometimes, we didn’t learn from those incidents.

There’s a sign in our academy gym that reads: “There are three things you need to know about mistakes. 1: Admit that you made a mistake. 2: Learn from your mistake. 3: Do not repeat the mistake again.” I never really applied this philosophy early in my career, but now it seems to be a fundamental of training. Constantly, and for good reason, we critique ourselves when identifying mistakes these days. We then take that constructive information and apply it to new techniques that allow us to safely and effectively carry out our assignments at future operations.

No matter how many years you have on the job, one of the most dangerous tasks you’ll be assigned on the fireground is working as the roof vent person on a building that you’re unfamiliar with, particularly its roof construction. This situation increases the probability for mistakes to be made, which increases the chances of injury—or worse.

Don’t Trust the Truss
Suppose you respond to a commercial building in your district at 0400 HRS with heavy fire on the first floor. The building looks recently built, but you’re not certain of its construction type. The roof is flat, which is one tip-off that you might have some sort of truss construction supporting it. What do you do?

Recently I discussed this type of flat-topped structure with some of my buddies from departments throughout the country. I was a little disturbed to find that some of their departments’ SOPs/SOGs include vertical ventilation from the roof level, even if a truss roof is identified. FDNY Chief Vincent Dunn (ret.) once wrote that if a fire in this type of building is serious enough to require roof ventilation, then it’s too dangerous to operate on the roof. I’ve personally worked at fires under Chief Dunn’s command, and if he thinks it’s dangerous, then it is.

Truss Construction 101
Below are some points you need to know concerning truss construction:
• This type of construction is used to span large areas and can be made from wood or steel.
• Open web steel joists are found in modern commercial structures. They span long distances. When operating in the interior of a building, and you see long spans not supported by columns, start thinking truss. Unprotected, lightweight, open web steel joists can collapse within 5 to 10 minutes if exposed to heavy fire.
• Every part of the truss is important to its stability. If one element fails, the entire truss may fail. Large spans and the interdependence of the trusses may cause an extensive collapse of the roof area.
• Different types of roof decking can cover the open web joists.

Truss Safety
The points below detail proper SOPs for truss roof operations.
• These roofs are not “working platforms” for firefighters. Engineers and architects don’t include firefighter safety in their design plans. When heavy fire is encountered, early collapse of the roof should be anticipated and members should not be committed to roof operations.
• Members on the roof must radio information to the incident commander (IC), such as the presence of heavy equipment and its location on the roof and, if ascertained, the roof construction.
• One of the IC’s primary concerns is the length of time the fire has been burning. A heavy fire condition will necessitate the withdrawal of interior units and the preparation for an exterior attack using large-caliber streams. Remember the size-up of the commercial building at 0400 HRS. Life hazard? You bet—to the firefighters.
• Some older commercial structures have wooden bow-string truss construction. Failure of one truss element can cause failure of the entire truss in the early stages of the fire. If a serious fire involves the roof portion of this type of truss, do not commit firefighters for roof ventilation.
• When venting the building, consider alternate options. Horizontal ventilation using door and window openings may provide some relief of smoke from the building. If the structure has large commercial doors, opening them may provide adequate ventilation. If horizontal ventilation isn’t effective, you must withdraw units and set up for an exterior operation.

This is just some information I wanted to pass on concerning a subject that’s constantly being updated and needs to be discussed. Don’t get me wrong, I’m not saying you should change your SOG/SOPs at these operations, but at the very least, you should discuss them and the safety of your firefighters.

Chief Fred LaFemina is a 24-year veteran of the New York City Fire Department (FDNY), presently chief of Rescue Operations. He has been with Special Operations for more than 20 years and is the task force leader for New York’s Task Force 1 Urban Search and Rescue team. He is also the operations chief on the USAR IST White Team. LaFemina has written many articles on fire operations and technical rescue and lectures throughout the country.

Copyright © Elsevier Inc., a division of Reed Elsevier Inc. All rights reserved.

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Comment by Tom Wheland on December 9, 2009 at 5:54pm
Bow string truss roofs are extremely dangerous and have killed many firefighters.

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