Page 48 - Occupational Health & Safety, December 2017

FIRE & EMERGENCY
Get the Facts About Fire Extinguisher Selection
In tough, high-hazard environments, fire extinguishers are put to the test.
BY SAM BORAAS
When fire breaks out on an industrial work site or in a manufacturing facil- ity, the impact—on people, property, and profitability—can be significant. It’s estimated that in the United States between 2009 and 2013, fire departments responded to an average of 37,000 industrial or manufacturing fires each year, resulting in:
■ 279 civilian injuries
■ 18 civilian deaths
■ $1 billion in property damage1
The stakes are high, and the risk is great. It’s not
surprising, then, that when decisions are made about
equipping work sites with fire extinguishers—the first line of firefighting defense—most organizations insist on quality. Often, decision makers defer to the UL fire ratings with the expectation that the higher the rating, the better the firefighting capability. For some fires, that’s true. But when it comes to fires in high-risk en- vironments, the opposite can be true.
The National Fire Protection Association recog- nized this anomaly in its 2007 NFPA 10, Subsection 5.5, which covers specific hazards including pressur- ized flammable liquids and gases, three-dimensional fires, and obstacle fires. For these Class B fires, the NFPA 10 technical committee concluded that ex- tinguisher size and flow rates should be the basis of extinguisher selection, not UL fire ratings, since the ratings on higher flow extinguishers tend to be lower than those on lower flow units.
Because Section 5.5 calls for selecting extinguish- ers that may have lower UL fire ratings, it is counter- intuitive to many. As a result, there remains a great deal of confusion about High Flow Fire Extinguishers in the marketplace today. How can lower-rated ex- tinguishers possibly be more effective in suppressing certain fires than those with higher UL ratings? Un- fortunately, the confusion can put people, property, and profitability at unnecessary risk.
Understanding the High-Risk, Low-UL-Rating Connection
When establishing a fire extinguisher Class B rating, one of the UL 711 considerations is discharge time— the length of time it takes for the dry chemical agent to discharge from the extinguisher. For certain fires, the longer the discharge, the better, and a longer dis- charge time may offer novice users time to correct any misapplication.
The slow rate of discharge, however, becomes problematic in high-risk environments where there is a greater likelihood of pressure fires, gravity fed/ three-dimensional, and obstacle fires. In these situa- tions, the operator needs an extinguisher that meets or exceeds a minimum of one pound per second flow rate. In other words, he or she needs a high-flow ex- tinguisher that delivers a lot of chemical—fast. Yet, because high-flow extinguishers tend to have lower UL ratings (because of UL’s discharge time criteria), they are sometimes dismissed as being less capable when, in fact, they are the optimal choice for these high-risk environments.
The NFPA 10 technical committee, recognizing the inconsistency, established this standard a decade ago; now, new test results validate that standard.
44 Occupational Health & Safety | DECEMBER 2017
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