One of the most recent additions to the lexicon of fire professionals is the term “lightweight construction.” It has become synonymous with truss-joist I-beams, laminated wood, and other engineered construction products. I feel, however, that this term is inaccurate and misleading. I would instead prefer to see the term “low-mass construction.”

Both of these terms are intended to alert firefighters to the fact that structural elements have less resistance to heat and fire and live loading than traditional dimensional lumber elements. Fire resistance is critical in terms of structural stability, flashover times, ventilation tactics, and so on—in fact, the whole strategy of offensive firefighting.

The late Frank Brannigan’s Building Construction for the Fire Service provides detailed explanations of why this is. Every firefighter, company officer, and chief officer should study this text thoroughly. In it, Brannigan stated: “In recent years, the economics of using geometry (e.g., truss shapes) over mass has had a tremendous effect on structures,”1 and “… the basic element of fire resistance is mass.”2

The distinction I seek goes back to high school physics classes and the definition of the terms “mass” and “weight.” According to Funk & Wagnalls Standard Desk Dictionary (1983),3 they are defined as follows:

Mass: 5. The volume or magnitude of a solid body; bulk; size.
Weight: 2. The measure of the force with which bodies tend toward the center of the earth, equal to the mass of the body multiplied by the acceleration due to gravitation.

When applying these two definitions to “lightweight” construction, there is obviously a problem with the term. Don’t stand underneath one of these lightweight structural components when it begins to “tend toward the center of the earth.” It’s going to leave more than just a bruise!

Basic fire science tells us that the longer an object can continue to absorb heat energy (because of its mass), the longer it will resist the effects of the heat energy: pyrolysis, ignition, degradation, and eventual loss of shape. Therefore, we should all be on the lookout for structural components with minimal mass, because they aren’t going to survive for long in a fire. And that is my point: Let’s be accurate and descriptive in our terminology so that it is intuitive and meaningful. “Lightweight” should become “low-mass.” Any discussion?

Al Hird
District Chief
Calgary (Can.) Fire Department

## Endnotes

1. Brannigan, Francis J. Building Construction for the Fire Service, Third Edition. Quincy, Mass.: National Fire Protection Association, 1992, 53.

2. Ibid, 330.

3. Funk & Wagnalls Standard Desk Dictionary.Lippincott & Crowell, USA, 1983.

## Warns of FDC corrosion problem

I want to make everyone aware of a major safety issue that I have discovered with imported (Chinese or Asian) fire department connections (FDCs). The ball bearings are made from steel or iron, which, of course, will rust when exposed to moisture (like all outside FDCs).

I have found many with hose connection swivels that cannot be rotated, even with a 24-inch pipe wrench, because the ball bearings corroded and rusted in place. If there is a fire, you would not be able to quickly couple a hose to this connection, which will delay operating at the scene.

Building owners may want to consider the following repair:

• Remove the set screw and swivel washer, and force lubricating oil into the opening until the swivel can be rotated by hand.
• At that point, remove the ball bearings by rotating the set screw opening to the “down” position, and rotate back and forth (use a cloth to catch the bearings).
• Remove the swivel.
• Using a wire brush, remove the accumulated rust and debris.
• If reusing the original bearings, coat them with oil; then place the swivel back into position and drop the bearing back in the set-screw opening. Replace the set screw, remove any excess oil, and replace the washer.

I have reported this to the listing agencies (Underwriters Laboratories and Factory Mutual). In the 28-plus years I have spent in the fire service, I have never found this problem in connections made in the United States.

Frank J. Herrick
Office of the Fire Marshal
Leawood (KS) Fire Department

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