Lelia Lawson, Betty Crown,

1
Moisture Effects in Heat Transfer Through
Clothing Systems for Wildlands Firefighting

• Lelia Lawson, Betty Crown,
• Mark Ackerman, Doug Dale
• Protective Clothing and Equipment Research
  Facility
• The University of Alberta

2
Related Literature

• turn-out gear with moisture barriers or single
  layers
• used TPP- or RPP-type test devices and end points
• many different moisture applications (amount
  location) results generally varied depending on
  moisture application

3
Objectives

• Examine the effects of location and source of
  moisture on heat transfer through materials
  comprising clothing systems worn by wildland
  firefighters.
• Examine alternative test procedures for measuring
  heat transmission through fabric systems.

4
Relevance To

• primarily wildland (forest) firefighters
• structural firefighters
• workers in the oil and gas industry
• others that may be exposed to a harmful heat
  source

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Wildland Firefighters

• Individuals who partake in the activities of
  fire suppression and property conservation in
  woodlands, forests, grasslands, brush, prairies,
  and other such vegetation, or any combination of
  vegetation, that is involved in a fire situation
  but is not within buildings or structures.
  (NFPA, 1987)

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Wildland Firefighters

• exposure to high temperature environments
• encounter moisture in many forms
• internal (perspiration)
• external
• spray from fire hoses
• rain water or dew
• bog or lake water

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Wildland Firefighters

• moisture may increase or decrease heat transfer
  through a clothing system depending on
• degree of moisture sorption
• location in the clothing system
• where it is located on the body
• its source
• its timing of application

8
Focus Group Interview

• focus group interview with wildland firefighters
  in Whitecourt, Alberta
• gain a better understanding of this environment
  and hazards to which wildland firefighters are
  exposed
• often exposed to internal and external moisture
• implication that moisture presence increases heat
  transfer through thermal protective clothing
  systems

9
Experimental Design

• Independent variables
• four different fabric systems
• five different moisture applications
• exposure to flame and radiant heat sources
• Dependent variables
• peak heat flux and total energy transferred
  through the fabric systems were measured

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Fabric Systems

• Outer layer / Underwear layer
• Aramid (221.5 g/m2) / 100 cotton jersey
  knit (176.5 g/m2),
• Aramid (221.5 g/m2) / Aramid rib knit
  (164.0 g/m2),
• FR Cotton (337.5 g/m2) / 100 cotton jersey
  knit (176.5 g/m2),
• FR Cotton (337.5 g/m2) / Aramid rib knit
  (164.0 g/m2).

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Moisture Application

• both outer and underwear fabrics oven dried prior
  to testing
• both outer and underwear fabrics conditioned in a
  standard atmosphere (21C and 65 relative
  humidity) prior to testing
• outer layer saturated prior to testing
• underwear layer saturated prior to testing
• both outer and underwear layers saturated prior
  to testing

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Flame Exposure (FE)

• specimens were tested using equipment for
  CAN/CGSB-4.2 No. 78.1 Thermal Protective
  Performance of Materials for Clothing with a
  6.4mm spacer
• heat flux was set at 83kW/m²
• flame remained under specimen for 10 seconds
• (heat flux and total energy data were collected
  for 60 seconds)

13
Radiant Exposure (RE)

• specimens were tested using equipment for NFPA
  1977 Standard on Protective Clothing for
  Proximity Fire Fighting, section 6.2 Radiant
  Protective Performance with a 6.4mm spacer
• heat flux was set at 10kW/m²
• the specimens were exposed for 100 seconds
• (heat flux and total energy data were collected
  for 100 seconds)

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Dependent Variables

• peak heat flux transferred through each specimen
  (fabric system) for both FE and RE
• determined total energy transferred through each
  specimen at 60 seconds (FE) or 100 seconds (RE)
• determined time to reach peak heat flux and time
  to reach 0.1 kJ for each specimen for both FE and
  RE

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Flame Exposure (83 kW/m2)
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Flame ExposureAramid Outer/ FR Cotton
Outer/ Cotton Underwear System Cotton Underwear
System
Heat Flux
Total Energy
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Radiant Exposure (10 kW/m2)
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Radiant ExposureAramid Outer/ FR Cotton
Outer/ Cotton Underwear System Cotton Underwear
System
Heat Flux
Total Energy
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High-Heat-Flux Flame Exposure
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Low-Heat-Flux Radiant Exposure
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Conclusions

• source and location of moisture do affect how
  heat is transferred through a clothing system
• at high heat fluxes, external moisture generally
  decreases heat transfer while internal moisture
  may increases heat transfer
• at low heat fluxes, internal and external
  moisture decrease total energy transferred

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Conclusions

• layering of outer and underwear materials do
  affect how heat is transferred through a clothing
  system when moisture is present
• at high heat fluxes, fabric systems with an
  aramid generally had a better thermal protection
  than fabric systems with a FR cotton outer layer.
  
• at low heat fluxes, thermal protection varied
  between fabric system depending on moisture
  application.

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Implications

• comfort
• heat stress/fatigue
• clothing systems
• choice of fabric system relevant to environment,
  or
• design system to accommodate all conditions
• standard test method development
• use of Stoll curve for an end point?
• one test condition?
• should consider end use

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Further Research

• examination of other moisture applications and
  their effect on heat transfer
• moistened internally during exposure
• moistened externally after exposure
• full scale garment system testing

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Acknowledgements

• Financial assistance from the Alberta Workers
  Compensation Board and the Department of Human
  Ecology and Faculty of Graduate Studies
  Research at the University of Alberta.
• The wildland firefighters employed by Alberta
  Land and Forest Service who participated in a
  focus group interview.

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