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Advances in Testing for Thermal Protective Performance Using

Instrumented Manikins

Alex HummelTextile Protection and Comfort Center (T‐PACC)

9/22/2016

Those at Risk of Flash Fire

Structural (NFPA 1971)

Soldiers Industrial (NFPA 2112)

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Flash Fire Environment• Flash fires are short duration (< 5 sec),

high intensity release of energy from ignition of combustible materials

• Can produce heat fluxes of up to 250 kW/m2

• Danger to Soldiers:– Improvised Explosive Devices (IED’s),

conventional munitions, and ignition of fuel sources

• Danger to Firefighters:– Backdraft/Flashover

• Danger to Industrial Worker:– Ignition of petrochemicals

Thermal Protective Performance (TPP)

• Measures heat flux passing through fabric to the wearer

• Heat generated by radiant quartz tubes and (convective) Meker burners

• Tested at high level heat (84 kW/m2 or 2.0 cal/cm2/s)

• Uses Stoll Curve to predict time to 2nd degree burn

• ASTM F2700 and F2703, Referenced by NFPA 1971

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Degrees of Burn

• First Degree:– Superficial burn that results in mild pain and redness

– Sunburns are a typical example

• Second Degree:– Occurs when partial thickness of dermis is burnt

– Results in blisters and moderate pain

• Third Degree:– Occurs when full thickness of dermis is burnt

– Results in nerve damage and scarring that may require a skin graft

Stoll Curve• Developed in the 1950’s by Alice Stoll and her research team

• Exposed forearm skin of subjects to known levels of radiant heat and measured time to “threshold blister” (2nd degree burn)

• Is only human testing to date defining parameters of burn injury

Heat Flux(W/m^2)

Heat Flux(Cal/cm^2*s)

Time to 2nd Degree Burn (sec)

3935 0.094 35.9

5903 0.141 21.09

11805 0.282 8.3

15740 0.376 5.55

23609 0.564 3

31479 0.752 1.95

39348 0.94 1.41

47218 1.128 1.08

55088 1.316 0.862

62957 1.504 0.713

70827 1.692 0.603

78697 1.88 0.522

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TPP Rating

• TPP(cal/cm2) = Intensity of heat flux exposure (cal/cm2s) x time to 2nd degree burn

• Example:

– Time to 2nd Degree Burn = 17.5 s

–Heat Flux Exposure = 2 cal/cm2s

– TPP = (17.5 s)x(2 cal/cm2s) = 35 cal/cm2 (NFPA 1971 standard criteria)

TPP Limitations• Constant high intensity heat

– This exposure is not indicative of what would be seen in field

• Direct skin contact– Pressure/compression from sensor block is not realistic either

• Does not account for air layers, additional fabric layers, orientation, shape, etc.

• Stoll curve intersection– Does not account for thermal momentum after test stops

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PyroMan

• More realistic: Account material shrinkage, garment fit, human contour, etc.

• Adult‐sized manikin made of heat resistant material

• 8 propane torches used to produce 84 kW/m2 (2.0 cal/cm2/s) over manikin surface

• 122 specially designed PyroCal heat flux sensors

• Heat flux data transferred to burn injury prediction model

PyroMan Results

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Human Skin Burn Model

Heat Flux

Heat Flux

Skin

Ω=Ptexp(∆E/RT)Burn Injury Equation

ρC∂T/∂ t = k∂2T/∂x2Heat Transfer in Skin

Stoll Curve to predict 2nd degree burns

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Potential Fire Manikin Advances

• Methods being studied in an effort to enhance the data collected during a PyroMan test, include:

– Site Specific Skin Thickness Values for Improved Anatomical Accuracy

– Total Energy of Each Sensor as a Comparison Tool

– Protection Factors as a Comparison Tool

– Longer Exposure Times for Similarity to TPP’s Time

Site Specific Skin Thickness• Human skin can vary throughout different regions of the body– Other factors include race, gender, certain health conditions, and age

• Currently, ASTM F1930 assumes one skin thickness value for entire body, based on forearm skin

• Originally developed for the PyroHands and PyroHeadprojects

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Site Specific Skin Thickness

*Initial results have shown that this can increase burn injury prediction significantly as compared to the current method

PyroMan Total Heat Absorbed

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

3 8 16 20 24 14 28 31 35 39 43 47 51 55 59 82 87 121 67 72 84 91 110

114 1 62 66 75 95 100

105

Ab

sorb

ed H

eat

Flu

x (c

al/c

m2 s

)

Arms Head Legs Midsection Upper Body

Head Sensors >19 cal/cm2s

***Total Heat Absorbed = 375.79 cal/cm2s*** ***Average Heat Absorbed = 3.08 cal/cm2s***

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Protection Factors for PyroMan• PyroMan is a dynamic test and flame exposure can be different at different sensors

• Used Protection Factors to try to normalize “hot spots”

• Protection Factor (PF):

PF = Extrapolated Energy from Nude Calibration (kJ)Total Energy from Sensor During Test (kJ)

Burn Injury Prediction

Control Suit

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Burn Injury Prediction vs. Protection Factor

Control

BIP PF

Protection Factor Comparison

ControlHeavy Weight

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Other Fire Flame Systems Tests• PyroHands:

– Measures thermal protective performance of gloves

– Set of stand‐alone hands made of heat resistant material

– Modified PyroCal sensor to fit into hands

– Sensors located in palm, dorsum, wrists, and fingers

Other Fire Flame Systems Tests

• PyroHead:

– Measures thermal protective performance of masks, helmets, balaclavas

– Head and neck manikin made of heat resistant material

– Includes 22 heat flux sensors in head and face

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RadMan• Developed for Wildlands Firefighter project

• Large radiant heat panels will expose manikin to 7.1 kW/m^2 heat flux

• Manikin skin is water‐cooled for longer duration testing

Articulated Fire Manikins

• Can improve upon current static manikin tests by:

– Causing break open for charred materials

– Introducing air pumping into the system

– Provide a more realistic in‐use scenario

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Shelter Testing• 5 propane torches used to create ~ 84 kW/m2 heat flux

• Inside Shelter:– Temperature probes 2 in. and 10 in. off ground

– Video camera

– Air sampling tubes for toxicity

• Heat flux sensors outside of shelter

• Flame exposure ended when 2 in. probe reached 160oC

Shelter Testing

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Adhesive Failure

Conclusions• Bench‐Level Testing is cost‐effective and good for initial R&D testing, but does not:– Provide all needed information about garment performance

– Give realistic estimations of end‐use scenarios

• System‐level testing provides important data on garment fit, design, and compensates for realistic flame movement around contour of body– For structural firefighter turnouts, more detailed systems‐level analysis is needed for better results comparison

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Thank You!

Dr. Alex HummelResearch Assistant Professor

North Carolina State UniversityCollege of Textiles1020 Main Campus Dr.Campus Box 8301Raleigh, NC 27695achummel@ncsu.edutextiles.ncsu.edu/tpacc/