Wildland firefighters work in unfavourable environments involving both heat and moisture. Moisture in clothing systems worn by wildland firefighters may increase or decrease heat transfer, depending on its source and location in the clothing system, location on the body, timing of application and degree of sorption. In this experiment, 4 outerwear/underwear combinations were exposed to 1 of 5 different conditions varying on amount and location of moisture. The fabric systems were then exposed to either a high-heat-flux flame exposure (83 kW/m(2)) or a low-heat-flux radiant exposure (10 kW/m(2)). Under high-heat-flux flame exposures, external moisture tended to decrease heat transfer through the fabric systems, while internal moisture tended to increase heat transfer. Under low-heat-flux radiant exposures, internal moisture decreased heat transfer through the fabric systems. The nature and extent of such differences was fabric dependent. Implications for test protocol development are discussed.

Flightsuit designs incorporating variation on four parameters of interest (one-piece vs two-piece, loose vs close fit, closure system, and seam type) were developed following a functional design process and using CAD procedures (Part I). Prototype garments were produced for each of three phases of instrumented mannequin testing of thermal protection. Fabrics used in the prototypes included a meta-aramid/carbon blend (phases 1 and 3), an FR viscose/meta-aramid blend (phases 2 and 3), and a meta-aramidlpbi blend (phase 3).Style, fit, and closure system each had small but significant effects on the thermal protection provided by flightsuits. Loose-fitting garments provided better protection than close-fitting ones if the fullness was controlled by appropriate closures. Close-fitting cuff closures on sleeves and pant legs were more effective than were zipper closures. A stand-up collar offered better protection for the neck than a convertible collar. Two-piece flightsuits provided somewhat greater protection than one-piece coveralls, mainly due to the effect of garment layering below the waist. These effects were detected when flightsuits were tested without underwear. The style effect was masked when the garments were worn over long thermal protective underwear, demonstrating the effectiveness of garment layering. Thus, for best assurance of thermal protection, flight personnel should wear long protective underwear under flightsuits at all times; in climates where this underwear might not be suitable, it is recommended that oneand two-piece flightsuits be made in a more loosely-fitting style and incorporate a stand-up collar and adjustable cuffs on sleeves and pant legs.

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A laboratory simulation was performed to study the thermal protective performance of fabric systems under low level thermal hazards in the range of 6.3—8.3 kW/m2 . Two approaches were used. The first used a method similar to the ASTM F 1939, radiant heat resistance test, while the second used a modification designed to capture the contribution to skin burn injury due to energy stored in the test specimens being released after the direct exposure had ended. Both dry and wet specimens were tested. In order to accommodate the prolonged exposure time a water cooled heat flux sensor was used to calibrate the radiant heat source and measure the energy directly transmitted through during the exposure and discharged later from the fabric systems. The Henriques Burn Integral (HBI) was adopted and programmed with a three layer skin model to predict the time required to achieve a second degree skin burn injury. The study investigated the thermal protection provided by the clothing with different layering and examined the effect of moisture under low level radiant heat exposures. In addition, the physiological burden associated with wearing the clothing was predicted and compared. The results obtained show the difference in measured protection level under low radiant heat from these two approaches and demonstrate that the stored thermal energy released from the clothing system significantly lowers the measured thermal protective performance.

Bench-scale tests measuring the thermal protective performance of textile materials do not capture the effect of thermal shrinkage, primarily because of the planar geometry of the test device. The performance of single-layer fabrics commonly used in protective garments is compared here following several protocols, including the use of a new cylindrical device as well as standard and modified ASTM, CGSB and ISO procedures, with and without a 6.35 mm air gap between the fabric and the sensor. Both the time to reach the second degree burn criterion and the time for the sensor to register a 248C temperature rise were measured. Fabrics that shrink had reduced thermal protection when measured with the cylindrical device, compared with other tests. Two-way analysis of variance indicated that, although the dependent measures differ significantly among fabrics, the nature and extent of those differences depend on the test used. One-way analyses of variance indicate that each method differentiates among the fabrics. However, most tests in which the fabrics are in contact with the sensor rank heaviest fabrics as the most protective. Among the tests incorporating a space between the fabric and sensor, those using the cylindrical device differentiate best between lighter fabrics that shrink and those that do not. Regression analyses of data from bench scale tests with data from instrumented mannequin tests confirm the superiority of the cylindrical device in capturing the effects of both thermal shrinkage and fabric integrity.