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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. Related Literature.

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moisture effects in heat transfer through clothing systems for wildlands firefighting

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

slide2

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
objectives
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.
slide4

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
wildland firefighters
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)
wildland firefighters1
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
wildland firefighters2
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
focus group interview
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
experimental design
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
fabric systems
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).
moisture application
Moisture Application
  • both outer and underwear fabrics oven dried prior to testing
  • both outer and underwear fabrics conditioned in a standard atmosphere (21°C 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
slide12

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)
slide13

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)
dependent variables
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
slide16

Flame Exposure:Aramid Outer/ FR Cotton Outer/ Cotton Underwear System Cotton Underwear System

Heat Flux

Total

Energy

slide18

Radiant Exposure:Aramid Outer/ FR Cotton Outer/ Cotton Underwear System Cotton Underwear System

Heat Flux

Total

Energy

slide19

High-Heat-Flux

Flame Exposure

slide20

Low-Heat-Flux

Radiant Exposure

conclusions
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
slide22

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.
implications
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
slide24

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
slide25

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.