Know Your Enemy #31

April 25, 2003
Hourly ratings cannot be relied on to predict the behavior of a building in an actual fire. It is dangerous to think otherwise
There are several tunes that I must play again and again. For instance, I see too many references to fire resistance ratings as if the rating hours are equivalent to clock hours at a fire.

Many builders and building officials seem to have the same erroneous belief. Some others seem to be pleased by the misunderstanding.

I urge every writer of articles or training material that whenever hourly ratings of fire resistance are mentioned, the following parenthetical note be included: "The hourly ratings are developed as comparative ratings of perfectly built samples of the type of construction, and the hourly ratings cannot be relied on to predict the behavior of a building in an actual fire. It is dangerous to think otherwise"

The comments to this effect, which you will find in chapter six of Building Construction for the Fire Service, were provided to me by Jack Bono the then director of testing at UL and later it's president.

The fallacy of depending on fire resistance ratings in so-called protected combustible structures such as garden apartments is set forth on pages 538-541 of BCFS3.

With respect to all fire resistance ratings, take note of the reference to the Society of Fire Protection Engineers 1975 statement: "The rate of fire development can create a condition that may tax or overpower traditional fire defenses"

Also note that in 1980, NBS (now NIST) researchers found that the test temperature the standard fire curve, is inadequate. This caused uproar in the industry. The Reagan administration, no friend of regulation of industry, zero funded fire research at NBS for five years. The funding was restored by Congress under the leadership of Senator Magnussen. There has been no further effort to revisit the dubious validity of the standard fire curve.


A fire officer emailed me a query on a new material he had found in a building. I entered the name into the search engine, and in a few seconds I knew all about it.


A Pennsylvania firefighter was recently killed by a chimney collapse. I do not know the facts in this case but chimneys in older houses can be particularly dangerous.

From Prince Edward Island, Canada to Sitka, Alaska, I have seen the same economical method of building chimneys. The chimney starts at a point where the stovepipe can reach. The chimney is supported on a wooden structure or brackets. Failure of the wood structure brings down the chimney.

Take note of any chimney that is fed by a stovepipe. See how it is supported. Record the item in the preplan and keep clear of it in a fire. Even all he way to the ground, chimneys are suspect. Most are sand lime mortar that may have little or no adhesion. The chimney may be leaning on the structure so the failure of the structure brings down the chimney.


If you would like to know about Frank Brannigan's unique career ask for 60 Years. It will be returned to you as a reply if you identify yourself. Address [email protected]


Voice Your Opinion!

To join the conversation, and become an exclusive member of Firehouse, create an account today!