Elizabeth M. Crown

Thermal protective performance of protective clothing used for low radiant heat protection

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.

Moisture Effects in Heat Transfer Through Clothing Systems for Wildland Firefighters

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/m2) or a low-heat-flux radiant exposure (10 kW/m2). 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.

Design and Evaluation of Thermal Protective Flightsuits. Part II: Instrumented Mannequin Evaluation

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 one-and 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.

Protection From Steam at High Pressures: Development of a Test Device and Protocol

Extensive use of pressurized steam in the oil and gas sectors has led to incidents where workers were seriously injured. In this study a test device and procedure to measure heat transfer through fabrics during steam exposure were developed and evaluated. Several factors were considered while designing the test device to simulate work site conditions. Fabrics were exposed to steam at 2 distances (50 and 100 mm) and 2 pressures (207 and 69 kPa). Theoretical considerations included heat and mass transfer, and fabric structure and performance properties. The test device and procedure differentiated well among both fabrics and exposure conditions. For all fabrics, maximum heat transfer was observed at highest steam pressure and shortest distance. Laminated and coated fabrics performed better than a fabric without such treatments.

Design and Evaluation of Thermal Protective Flightsuits. Part I: The Design Process and Prototype Development:

An aviators flightsuit must protect against hazardous thermal environments. In addition, it must be comfortable, fit properly, allow for mobility, and meet several other expectations for military clothing. A systematic approach to designing protective garments is needed to ensure acceptance on all criteria. The purpose of this study was to design and evaluate garment systems for optimum thermal protection for Canadian Forces flight personnel and to determine the effect of selected garment parameters (style, fit, closure system and seam type) on thermal protection. Part I focuses on the design process. Orlandos (1979) functional apparel design process served as the conceptual framework; for this study the process incorporated a literature search, material analysis, focused group interviews and movement analysis to develop design criteria and specifications for eight alternative flightsuits incorporating the parameters of interest. The design criteria included thermal protection, other functional requirements, psychological requirements, production and maintenance. Patterns for the garments were developed using AutoCAD® and PCPattern® software. The design process allowed systematic consideration of all related aspects of the problem. Evaluation of the garments is described in Part II.

Characterization of the Combustion Process of Flame Resistant Thermal Protective Textiles in the Presence of Oily Contaminants: Effects of Contamination and Decontamination:

This paper reports two experimental studies wherein the combustion process of flame resistant (FR) thermal protective textiles is characterized in terms of thermal decomposition and heat release parameters before and after contamination and in terms of heat release parameters after contamination and decontamination. Aramid and FR cotton/nylon decomposed at higher and aramid/FR viscose at lower temperature in the presence of oil. Oil interferes with thermally induced interactions between aramid and FR viscose, altering the thermal decomposition rates and formation of char, and thereby increasing the effectiveness of the flame retardant present in the viscose. It is apparent that oily contaminants present in FR fabrics affect the initiation of the thermal degradation and formation of char. All contaminated FR fabrics showed significantly higher peak heat release rate (PHRR), total heat release (THR) and effective heat of combustion (EHC) compared to uncontaminated ones. Oily specimens laundered with no detergent or prewash product had higher PHRR, THR and EHC compared to other treatments regardless of the fabric type or number of contamination/decontamination cycles. Heat release increased with increased number of contamination/decontamination cycles for most laundry treatments for all FR fabrics. FR cotton/nylon had the highest and aramid had the lowest PHRR and THR whether specimens were uncontaminated, contaminated or decontaminated. In this study heat release from FR fabrics increased with increased oily contamination.

How clean is clean enough? Maintaining thermal protective clothing under field conditions in the oil and gas sector.

The purpose of this research was to develop practical care procedures to help maintain the protective quality of flame resistant workwear laundered by workers in the field. Based on observed field conditions, experiments were conducted that simulated domestic laundry procedures. The first experiment involved two flame resistant (FR) fabrics, contaminated or not contaminated with oil. Independent variables also included detergent type and laundry pre-treatment. Other laundry parameters were controlled. Results indicated that it is easier to maintain the FR performance of the FR-treated blend than it is for the aramid fabric. It is hypothesized that energy generated by initial ignition of oil on the specimens triggers the FR mechanism of the treatment, which in turn inhibits further combustion. A second experiment using larger specimens and a domestic washing machine also supported the hypothesized mechanism.

Evaluation of Functional Fit of Chemical Protective Gloves for Agricultural Workers

The purpose of this study was to evaluate the functional fit of commercially available protective gloves recommended to agricultural workers and to investigate the effect of polymer type, thickness of glove materials, and glove shape on such fit. The study was conducted in two parts. First the hand dimensions of the user population were estimated by conducting an anthropometric survey of 380 agricultural workers. This was followed by a fit evaluation of four test gloves by 38 farmers whose hand dimensions were representative of the user population. Fit was assessed by subjective evaluations of 15 specific hand dimensions for each glove and by conducting two standardized dexterity tests with participants bare-handed and wearing each of the four gloves. Significant differences in fit were found among gloves differing in polymer type, thickness and shape. Thinner gloves made from flexible polymers gave the most acceptable fit. Major design and sizing problems were identified for each of the four gloves. Gloves that fit snugly and enabled participants to complete dexterity tests at a rate comparable to bare hands received the highest subjective fit ratings. To enable agricultural workers to achieve optimum performance while completing fine manipulative tasks, the fit of gloves, especially in the fingers, must be improved.

Attitudes and Behavioral Intentions of Agricultural Workers Toward Disposable Protective Coveralls

The purpose of this study was to understand better the behavior of grain farmers toward the use of disposable protective coveralls by measuring beliefs, attitudes, and other components of the Fishbein-Ajzen theory of reasoned action and determining relationships among these components. The results indicate that most of the farmers believe that wearing disposable coveralls would provide the best method of protection and a more secure feeling about pesticide use. Respondents believe important referents such as their spouses will likely suggest that disposable coveralls should be worn while applying pesticides. Overall, farmers have positive attitudes and behavioral intentions. Pearson correlations and regression analyses indicate significant relationships among all components of the model. Attitude and subjective norm together provide considerable influence on behavioral intention with attitude being the stronger component. Thus the Fishbein-Ajzen model was applied effectively to the behavior of wearing disposable protective coveralls.

Quantity and Distribution of Oily Contaminants Present in Flame-resistant Thermal-protective Textiles

This paper reports an experimental study wherein the quantity and distribution of oily contaminants present in flame-resistant fabrics (FR) after contamination and decontamination was determined using radiotracer analysis and scanning electron microscopy. The experimental variables were fabric type, laundry treatment, and number of contamination/decontamination cycles. Laundry treatments involving a pre-wash product were the most effective in removing oil from all FR fabrics regardless of the number of contamination/ decontamination cycles. Accumulation of oily contaminants was noted after five contamination/ decontamination cycles regardless of the fabric type or laundry treatment. FR cotton/nylon retained the most residual oil for all laundry treatments. No oil remained in the interior of the aramid, viscose, and nylon fibers, but rather remained on the surface so that it was removed easily during decontamination. A significant quantity of oil was located in the interior of the cotton fibers, making it difficult to remove during decontamination.