How Cool Is Cool?

Heat stress or heat strain remains a primary contributor to firefighter deaths, illnesses, and injuries.

Keeping It Safe |

Heat stress or heat strain remains a primary contributor to firefighter deaths, illnesses, and injuries.
Robert Tutterow

In addition to the heated fire environment, firefighters must wear protective clothing that would keep people comfortably warm in subfreezing temperatures. Now that I have stated the obvious, where does this lead?

First, a bit of background on “how cool is cool?” For decades, those within our departments who determine the specifications for turnout gear have had to balance the proper thermal protective performance (TPP) with the breathability of the gear—i.e., the total heat loss (THL). Manufacturers are always trying to design ways to maximize this balance, and researchers are continually pursuing ways to develop and quantify the heat stress issue.

As the fire service wrestles with this issue, it is only natural that comparisons of materials and designs be assessed. In an ideal world, the quantitative data for measuring TPP and THL would be based on the entire ensemble with human subject testing. And, therein, lies part of the problem with the words “human subject.” All humans are different, and thus testing results are subjective. For products to be accurately assessed (tested) scientifically, the testing environment must be consistent from one venue to the next. In the scientific community, this is referred to as having consistent test results from laboratory to laboratory.


Reducing Cancer and Heat Stress LODDs

With all this in mind, Textile Protection and Comfort Center (TPACC), a division of the College of Textiles at North Carolina State University, recently revisited the subject of the THL measurement in a three-year study. The study was funded by an AFG Research Grant and was done in conjunction with the Illinois Fire Service Institute and F.I.E.R.O. The results of the research will be presented to the NFPA 1971, Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting, technical committee as a public input for consideration to include in the next revision of NFPA 1971.

The premise of the study is that the current THL measurement, which was first introduced into the NFPA 1971 standard in 2000, is based on a cool (room temperature) environment. There is logical thought that firefighters might be better served if the test were performed in a more heated environment. Fortunately, there is such a test; it is referred to as Ret Testing and is described as the measurement of the resistance to evaporative heat loss. The lower the Ret value, the less resistance to moisture transfer and therefore the higher breathability, whereas in THL, the higher the number, the higher the breathability. Yes, that can be confusing, and the research team at North Carolina State is working on developing wording to submit to the NFPA 1971 technical committee for consideration that will minimize the confusion. In fact, there is a likelihood the term Ret Testing or Ret Test results will not be mentioned in the standard, as there might be a way to further define the THL test measurement.

The quick and dirty bottom line is that the research showed that Ret Testing is a very valid measure, especially in warmer, more humid atmospheric conditions. Therefore, fire departments might be wise not to wait until the NFPA 1971 technical committee decides whether to include Ret Testing as part of its requirements. Remember, there is nothing that precludes a fire department from specifying additional minimal NFPA requirements if they do not void existing requirements. If your department operates in environments that are frequently warm and humid, it is definitely a worthy consideration.

All the turnout gear manufacturers are now familiar with this test, although it is not a requirement. If you ask your manufacturer about protective garments with a low Ret Testing number and it is not familiar with it, I would shy away from the manufacturer, as it is not paying attention to the latest industry research.

The fire service should be most appreciative of this type of research and the AFG grant funding that makes it possible. As in almost all research, this research showed promise for additional research that would improve heat stress of turnout gear—for example, the color of the outer shell (stay tuned!) and the level of contamination on the gear.

Stay cool!

ROBERT TUTTEROW retired as safety coordinator for the Charlotte (NC) Fire Department and is a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board. His 40-year career includes 10 as a volunteer. He has been very active in the National Fire Protection Association through service on the Fire Service Section Executive Board and technical committees involved with safety, apparatus, and personal protective equipment. He is a founding member and president of the Fire Industry Education Resource Organization (F.I.E.R.O.).

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