In May of this year Bret Butler, who works in the Fire Behavior Research Work Unit at the Fire Sciences Laboratory in Missoula, Montana, issued a new rule on the size of a safety zone. Mr. Butler revised it two months later in July, and after an additional four months he changed it still again in November.
The calculation of the size of a safety zone is somewhat complex for a firefighter in the heat of battle, and these various guidelines can only be used if the firefighter on the ground is carrying the latest written directions about how to do the math. While it is laudable that researchers are working to improve the safety zone guidelines, changing them every two to four months is too confusing.
In the video (webinar) below the new revision is discussed in detail in the one hour and 15 minute presentation, including questions. (A three-minute executive summary version would be very much appreciated.) This new November, 2014 version of the “Preliminary Proposed Safety Zone Rule” appears at 44:00. The fact that it is called both preliminary and proposed leads us to believe there will be still more changes in the near future.
Below is the description of the December 2, 2014 webinar, presented by Mr. Butler.
Current safety zone guidelines for wildland firefighters are based on the assumption of flat ground, no wind, and radiative heating only. Recent measurements in grass, shrub and crown fires indicate that convective heating can be significant especially when wind or slope are present. Measurements and computer modeling supports this finding and suggests that convective energy transport should be considered when assessing safety zone effectiveness any time wind or slope is present. The results of the research are presented along with recommendations for modifications to current safety zone guides.