Analysing Performance of Protective Clothing upon Hot Liquid Exposure Using Instrumented Spray Manikin

Transcription

1 Ann. Occup. Hyg., Vol. 57, No. 6, pp , 2013 The Author Published by Oxford University Press on behalf of the British Occupational Hygiene Society doi: /annhyg/mes109 Analysing Performance of Protective Clothing upon Hot Liquid Exposure Using Instrumented Spray Manikin Yehu Lu 1,2, Guowen Song 2 * and Jun Li 1,3 1 Protective Clothing Research Centre, Donghua University, Shanghai, China; 2 Department of Human Ecology, University of Alberta, Edmonton, Canada; 3 Key Laboratory of Clothing Design and Technology, Ministry of Education, Shanghai, China Received 16 September 2012; in final form 4 December 2012; Advance Access publication 16 January 2013 Hot liquid hazards existing in work environments present a common risk in workplace safety in numerous industries. In this study, a newly developed instrumented manikin system was used to assess the protective performance provided by protective clothing against hot liquid splash. The skin burn injury and its distribution for the selected clothing system were predicted and the effects of clothing design features (fabric properties and garment size) on protective performance were investigated. The air gap size and distribution existing between protective clothing and human skin were characterized using 3D body scanning, and their relation to skin burn injury was identified. The mechanism associated with heat and mass transfer under exposure to hot liquid splashes was discussed. The findings provided technical bases to improve the performance of protective clothing. For protective clothing design, minimizing mass transfer through clothing system is very important to provide high performance. Keeping the air gap between the garment and the human body is an essential approach to improve thermal performance. This can be achieved by proper design in size and fit, or applying functional textile materials. Keywords: air layer; hot liquid splash; instrumented manikin; skin burn; thermal protective clothing Introduction Workers might be exposed to different kinds of hazards such as chemical, heat and flame, steam, hot liquid, or molten metal scald burn injuries during working (Norman et al., 1985; Makinen et al., 2008; Sati et al., 2008; Ceballos et al., 2011). Various functional textile materials are used to prevent excessive heat and mass transfer from the working environment (hazards) to the human body. However, traditional protective ensembles worn by workers cannot provide sufficient protection against all hazards. It has been reported that the highest proportion of burns results from contact and scalds (Taylor et al., 2002). Based on the *Author to whom correspondence should be addressed. Tel: ; Fax: guowen.song@ualberta.ca analysis of collected burn injury data, hot liquid hazards were shown to be a considerable risk in workplace safety for numerous industries. Analysing steam transfer through different textile layers, Rossi et al. (2004) found that heat transfer depended on the water vapour permeability, thickness, and thermal insulation of the specimens. It was indicated that impermeable materials provided better protection against hot steam than semipermeable ones. Adding a spacer behind impermeable fabrics showed a higher increase in protection than semipermeable fabrics. The pre-wetting of the fabric surface by water spray decreased the steam protection; however, the moisture produced by a sweating cylinder showed a positive effect from continuous sweating (Rossi et al., 2004). Recently, a test device and procedure to measure heat transfer through fabrics during 793

2 794 Y. Lu, G. Song and J. Li high-pressure steam exposure were developed (Sati et al., 2008). Using this apparatus, the protective performance provided by the selected fabrics can be differentiated in terms of peak temperature, peak heat flux, and total absorbed energy (TAE). For each fabric, both the distance between steam jet and fabric and steam pressure had significant effects on thermal performance. Laminated and coated fabrics showed better performance than those without such treatments. The protection of different protective fabrics including aluminized and non-aluminized fabrics against molten iron has been evaluated in a controlled splash test. The ability to resist molten iron is correlated with fabric properties, including thickness and weight, air permeability, and the flammability characteristics (Barker and Yener, 1981). Makinen et al. (2008) have developed a test method, which could reliably identify materials and material combinations for protective clothing and other necessary personal protective equipment for recovery boiler workers. Jalbani et al. (2011) have modified the hot water protection device and procedure described in ASTM F2701. The test device was able to differentiate among the fabrics in terms of heat flux and absorbed energy when exposed to hot water. It was concluded that fabric structure and properties were the key factors in protective performance. The position of the membrane in fabric systems affected the thermal performance (Jalbani et al., 2011). Air permeability of the fabric was a critical factor in determining the protection against hot water (Jalbani et al., 2011; Ackerman et al., 2011b). It was found that minimizing the mass transfer during hot liquid splash was the most important mechanism to provide high-level protective performance (Lu et al., 2012a). In addition, the investigation of mass transfer characteristics through protective materials under the same exposure condition has been conducted (Lu et al., 2012b). The results clarified the effect of fabric surface properties, fabric thickness, fabric combination, and membrane on liquid absorption and penetration. High temperature of the liquid also decreased the surface energy of the fabric, resulting in more mass transfer through the fabric system. Furthermore, the relationship between mass transfer and protective performance was discussed in our previous study (Lu et al., 2012a). The effect of liquid flow on skin burn injury of protective fabrics exposed to hot liquid was investigated and the contribution of stored energy to thermal protective performance was explored (Gholamreza et al., 2012a,b). Instrumented manikins have been demonstrated to be a very helpful tool for characterization of the protective performance of full-scale garments. In the design of thermal protective clothing, the air gap between clothing layers and the body is one of the most important factors governing energy transfer and thermal damage to the skin (Torvi et al., 1999). Kirkpatrick et al. (1982) found that garment style of trousers had great influence on effectiveness of protective performance. Crown et al. (1998) concluded that loose-fitting protective clothing could provide better thermal protection than close-fitting garments and the garment style and closure system also had a small but significant effect on thermal protection. To investigate the effect of body geometry, garment style, and fit on thermal protection, a flash-fire instrumented female mannequin evaluation system was used (Mah and Song, 2010). Furthermore, the protective performance of garments was evaluated by using a copper manikin exposed to a steam climate chamber (Desruelle and Schmid, 2004). The test results obtained from fabrics and garments were in good agreement. Water vapour impermeable fabrics and garments provided greater protection against hot steam. Moreover, the thicker fabrics and garments provided better performance (Desruelle and Schmid, 2004). A loosefitting impermeable garment increased the level of thermal protection above that of a thin garment. It was also mentioned that the thermal properties under steam conditions might be different from those measured under typical ambient conditions (Desruelle and Schmid, 2004). Hot liquid splash with pressure may apply compression force to the clothing, resulting in garment deformation and physical properties change, which may affect heat transfer in protective clothing and its discharge of stored thermal energy. Preliminary full-scale hot water spray tests using a manikin were carried out and the material combinations used in protective coveralls have been compared (Ackerman et al., 2011a). The results demonstrated that impermeable clothing provided better protection. The existing testing standards of thermal protection against hot fluid are used to characterize the thermal properties of fabrics. Few researches on hot liquid splash protection of full-scale garment have been carried out. The understanding of the mechanism associated with heat and mass transfer when protective clothing is exposed to hot liquid is limited. The purpose of this study is to investigate the effect of clothing design features and fabric properties on protective performance.

3 Performance of protective clothing upon hot liquid exposure 795 In addition, the study aims to explore the heat transfer mechanism from hot liquid splash hazards to human skin through protective clothing. The overall objective is to make recommendations for textile engineers and functional clothing designers to develop high-performance protective clothing to reduce scald burn injuries. Experimental Test garments A number of protective garments made of permeable, semipermeable, and impermeable fabrics were used. These were commercially available in the market for industrial workers. In addition, coveralls in three sizes (close-fitting, fitted, and loose-fitting garments) were employed to understand the effect of garment fit on protective performance. The detailed configurations of testing coveralls are shown in Table 1. A non-contact VITUS Smart 3D whole-body laser scanner by Human Solutions was used to characterize the size of air gap between the clothing and manikin surface. Garments G1 G7 and garments G10 G12 are coveralls, but garments G8 and G9 consist of a separate jacket and bib pant. In addition, the G7 is a double-layer coverall with G6 as the outer layer. They were all provided by the thermal protective clothing manufacturers. All the experimental garments consisted of a double-layer foldover collar and a top fly in the front centre as well as a horizontal segment line at the waist. Pockets such as chest patch pockets with flap, rear patch pockets, and in-seam pockets were included in the designs. Reflective tape was also stitched on at the shoulder, cuff of sleeve and leg, and back. Testing apparatus An instrumented manikin testing system was used to study the protective performance against hot liquid (water) spray, as shown in Fig. 1. The instrumented mannequin with size of 40R (as shown in Fig. 1a) was made from fibreglass and resin and was equipped with 110 skin simulant sensors, which were uniformly distributed over the surface of the mannequin (Mah and Song, 2010). The manikin was hung by the head and fastened at the feet by two fetters to keep an upright posture. Four groups of cylinder spray jets automatically controlled by valves, as shown in Fig. 1b, were used to spray the manikin trunk. Each group consisted of three bottom-up nozzles. Hot water was simultaneously ejected by 12 nozzles for testing coveralls in this study. The hot fluid was heated up by superheater and pumped from a 20-l tank by a motor. The pressure of the hot liquid was regulated by the circulation valve. For this study, pressure of 250 kpa was set before exposure to mimic the hot water splashes in industrial work scenarios (Ackerman et al., 2011a). During exposure, the heat flux at the surface of the mannequin and its variation with location and time were determined by a computer-controlled data acquisition system and analysed by programme to determine the skin burn distribution over the body and the TAE during test (Crown and Dale, Table 1. Specification of the testing protective clothing. Garment code Size Fibre content Fabric weight (g m 2 ) Air permeability a (cm 3 cm 2 s 1 ) Permeability G % Nomex Permeable 25.1 G % Cotton and 12% nylon Permeable 26.1 G % Cotton and 12% nylon Permeable 27.1 G % Cotton and 12% nylon with Semipermeable 29.7 polymer finishing G % Cotton and 12% nylon with Semipermeable 27.8 polymer finishing G % Cotton Permeable 33.7 G7 42 Cotton/quilted lining Arcxel Permeable 38.5 G8 42 Polyvinyl chloride-coated cotton Impermeable --- G9 42 Polyurethane-coated Aramid knit Semipermeable --- G % Cotton and 12% nylon Permeable 25.5 G % Cotton and 12% nylon Permeable 28.0 G % Cotton and 12% nylon Permeable 31.0 Average air gap (mm) a The fabric air permeability is tested according to ASTM D (2004). The --- means the air gap size is not measured.

4 796 Y. Lu, G. Song and J. Li Fig. 1 (a) Instrumented manikin with sensors and (b) spray jets. 1992). The bio-heat transfer model in human skin used to predict the temperature history of the basal layer was described in the study of Mah and Song (2010). Henriques Burn Integral (Henriques and Moritz, 1947) was applied to predict secondand third-degree burn time. The procedure and parameters were described in ISO In addition, a video of high resolution was used to record the water spray exposure. Protocol The testing coveralls were preconditioned in a standard climate of 20 C and 65% relative humidity for at least 24 h prior to testing. The 3D body scanning was carried out to calculate the air gap between protective clothing and human skin (manikin surface). Three scanning tests for each ensemble were conducted. A specific procedure was applied to dress the spray manikin in the same manner as the scan manikin to reproduce the air gap distribution as accurately as possible (Mah and Song, 2010). Protective clothing was dressed on the manikin according to pictures taken during 3D body scanning to ensure a similar wear condition. The hot water was heated to 85 o C and 10 s exposure time was used. The exposure process of the tested garments was recorded by the video camera in front of the manikin. The data acquisition system was set for 60 s to record sensor surface temperature change. The percentage of second- and third-degree skin burn, TAE, and skin burn distribution were predicted by the testing system. Three replicates of each garment were tested. Statistical analysis The analysis of variance test was carried out by Statistical Package for Social Science version 16.0 to differentiate thermal protective performance of protective clothing against hot liquid spray. Effects of garment size and fabric properties were all analysed. The Student-Newman Keuls multiple range test and Dunnett T3 post hoc test were employed. P < 0.05 was considered significant. Results and Discussion The percentage of second- and third-degree burn and average TAE of all the sensors are shown in

5 Performance of protective clothing upon hot liquid exposure 797 Table 2. Burn injury and TAE of tested garments. Garment code Second-degree burn (%) (SD) Third-degree burn (%) (SD) Total second- and thirddegree burn (%) (SD) TAE (cal cm 2 ) (SD) Nude (0.63) 0.53 (0.53) (0.63) a (0.066) b G (4.51) 8.17 (4.33) (5.60) b (0.183) c G (1.30) 2.17 (1.93) (0.83) c,b (0.070) d G (0.28) 2.40 (2.26) (2.18) c (0.220) d G (2.01) 0.00 (0) 8.92 (2.01) e (0.103) e G (1.92) 0.00 (0) 6.35 (1.92) e (0.065) e G (5.50) 0.00 (0) (5.50) f (0.109) f G (0) 0.00 (0) 0.00 (0) g (0.015) g G (0) 0.00 (0) 0.00 (0) g (0.051) g G (0) 0.00 (0) 0.00 (0) g (0.033) g G (2.48) 0.70 (0.62) (2.06) d (0.169) h G (2.12) 1.17 (1.02) (1.65) d,h (0.087) h G (0.88) 0.65 (0.56) (1.28) h (0.157) h SD, standard deviation. a,b,c,d,e,f,g,h In each column, means with the same letter superscript indicate homogeneous subsets (highest and lowest means are not significantly different) when subjected to the Student-Newman Keuls multiple range test (P < 0.05). Table 2. In the nude manikin exposure, 77.3% skin generated second-degree burn and 0.53% skin received third-degree burn. The head and part of the arms did not predict severe skin burn injury. The maximum manikin surface area that could develop burn was 88% (including 7% for the head) since the hands (5%) and feet (7%) were not equipped with sensors (Mah and Song, 2010). The TAE was cal cm 2. The different models of protective clothing provided distinct thermal protection against hot liquid spray with pressure in terms of total second- and third-degree skin burn injury and TAE. The tested garments can be divided into eight categories based on the statistical analysis. There was no burn observed while wearing garments G7 G9. However, >50% skin developed irreversible burn injury while wearing G1 or G2. Effect of fabric properties on thermal performance It was found that G1 provided the least protection against hot water splash. There was as much as 48.07% second-degree burn and 8.17% third-degree burn. The third-degree burn mainly occurred at pelvis and thigh. This was significantly different from the nude test. The TAE was cal cm 2, which was a little lower than that of nude spray. There was a total of 51.8% irreversible burn injury (49.63% second-degree burn and 2.17% third-degree burn) while wearing G2. Garment G3 showed 49.27% burn over the body. There was no significant difference in thermal protection provided by G2 and G3. Nearly 40% skin burn occurred over the manikin covered by permeable garment G11. As low as 8.92% seconddegree burn occurred and cal cm 2 TAE was absorbed when the manikin was dressed in G4. Garment G5 showed similar performance to G4. There was 16.77% skin burn while wearing G6, which showed better performance than other permeable garments G1 G3 and G10 G12. There was no burn observed while G7 G9 were worn. The TAE was 0.447, 0.528, and cal cm 2, respectively. In addition, the TAE was negatively correlated with total skin burn injury (P < 0.001). Based on the results obtained in the study, it was indicated that this manikin system could differentiate the selected thermal protective clothing used in industries (Fig. 2). The study indicated that garments made of fabric with different properties provided different thermal protection. Semipermeable and impermeable garments provided good protection against hot liquid spray, which was consistent with results in the study of Ackerman et al. (2011a). This was due to the blocking or minimizing of mass transfer. In previous bench-scale tests, it was confirmed that mass transfer was the critical factor influencing heat transmission (Ackerman et al., 2011b; Lu et al., 2012a). The best protection in G9 was also related to the high thickness of fabric and design configurations. The jacket and bib pant overlapped at the torso and pelvis, providing extra protection,

6 798 Y. Lu, G. Song and J. Li Fig. 2. Thermal protective performances of different garments. as shown in Fig. 3. Impermeable garment G8 had a similar design pattern, showing comparable thermal protection. Comparison of G4 with G3 demonstrated the importance of repellence of water penetration during exposure. These two garments were made of the same 88/12 flame resistant (FR) cotton/nylon, but the G4 was treated by polymer finishing with Nextec technology. The water repellent polymer finishing showed a significant effect on thermal protection. It confirmed the critical effect of minimizing mass transfer on thermal protection against hot liquid spray. The heat transfer from the garment to skin was mainly through conduction and radiation. The fibre content and finishing of G5 were the same as those of G4, but the weight of G5 was higher than that of G4. However, there was no significant difference in overall performance between G4 and G5. This showed the fabric weight did not affect the protective performance of semipermeable garments. Among permeable garments, G6 provided better protection. The average air gap of G6 was the highest among the tested coveralls (see Table 1). It was observed that G6 maintained its shape relatively well except at direct water spray locations during exposure to the hot water spray, as shown in Fig. 4a, and thus the air gap entrapped inside the garment was almost maintained and, as a result, this decreased the heat transmission to the Fig. 3. Overlap of jacket and bib pant in G9. sensors. The burn injury that occurred at the torso and thigh might be related to the garment contacting the skin (zero air gap) during exposure, caused by the pressure of the water spray at the torso and the water flow along the pelvis and thigh. In addition, the permeable fabric absorbed water during water spray, and when the fabric contacted the skin, the direct exchange of liquid water occurred, resulting in heat discharge (Keiser et al., 2008). Due to the wicking effect, this liquid is distributed over a larger area and further enhances the inhomogeneous heat and mass transfer (Umeno et al.,

7 Performance of protective clothing upon hot liquid exposure 799 Fig. 4. Garment contour of G6 and G1 during hot water spray. 2001). These fundamental factors were applicable to all permeable garments. Garment G7 was double layered and the outer shell was the same as G6. The extra thermal liner significantly increased the thermal protective performance. Garment G2 and G3 were made of FR cotton/ nylon with different weight, and thus the overall burn injuries were similar. These fabrics were water permeable; thereby, the hot water penetrated through the garment if the water spray compressed the clothing surface. It has been confirmed that the mass transfer had a great effect on the thermal protection. However, the mass and average air gap size of G3 were higher, resulting in slightly but not significantly higher performance. The manikin test showed that the protective performance of G11 was better than that of G3. The average air gap size of the two garments was approximately the same. In addition, the fibre content and fabric mass of G3 and G11 were the same, but they were provided by different manufacturers. Test results indicated that the surface properties of the two garments were different and resulted in different protective performance, confirming the importance of surface finishing. The worst protection found was provided by G1. This might be caused by the least average air gap combined with a soft permeable fabric. During exposure, the high-pressure water spray compressed the fabric on the torso, as shown in Fig. 4b. On one hand, much water penetrated through the fabric; on other hand, the fabric was soaked with water and contacted with the skin, thereby much energy was transferred to the skin and caused severe burns. In addition, there was higher percentage of third-degree burn than in the nude test. This might be related to the discharge of stored energy after water spray. Much water was absorbed in the garment during exposure, which transmitted energy to the sensor after exposure. During nude manikin exposure, the water can flow away, and thus there was little stored energy contributing to third-degree burn. If the total burn surface area of second-degree burn exceeds 20%, or the percentage of thirddegree burn is beyond 5% of body surface, a victim at age of years should be sent for hospitalization according to American Burn Association Criteria (Berry et al., 2006). Currently, a burn injury <20% of the whole body is one of the protective performance criteria for a military flame/

8 800 Y. Lu, G. Song and J. Li Fig. 5. Thermal protective performances of garments with different sizes. thermal protective clothing system (Kim et al., 2002). Therefore, total percentage of second- and third-degree burn <20%, with third-degree burn <5% is proposed as the criteria to consider the thermal protective performance at an acceptable level. Based on the criteria, garments G4 G9 provided good protection from hot liquid spray, while the other garments failed to protect the safety of wearer. Effect of garment size on thermal protection The thermal protection provided by coveralls made in different sizes with the same fabric and design features is compared in Fig. 5. The sizes of garment showed an effect on thermal protection against hot water spray in terms of total burn injury. The statistical analysis showed that total burn injury for size 44 was significantly different from that of size 40 (P = < 0.05). The difference in skin burn injury was only 5.9%. There was no significant difference between garment of size 40 and size 42 (P = > 0.05). There was also no significant difference between garment of size 42 and size 44 (P = > 0.05). Meanwhile, there was no significant difference in TAE among the three garments (P = > 0.05). The air gap increased with garment sizes (shown in Table 1). It was noted that the studied garments in different sizes were permeable and the garment absorbed much water during exposure, resulting in fabric contacting the manikin surface at torso, pelvis, and leg as shown in Fig. 6. This indicated that the effect of air gap on thermal protection against hot water spray was minimal for these permeable garments. From an ergonomic viewpoint, a wrong size garment may constrict human body movement and also the added weight will cause more energy consumption (Dorman, 2007; Wang et al., 2011). Considering both ergonomic and protection factors, the proper fit of garment is recommended. In a previous study on thermal protective clothing under exposure to flash fire, Crown et al. (1998) found that loose-fitting garments showed better performance than tightfitting garments if the garment integrity could be controlled. For garments with severe shrinkage at high temperature, the positive effect of loosefitting garments was minimal. The spray manikin test in this study indicated that the effect of garment fit on thermal protection from hot liquid hazards was different from that against flash fire. Distribution of skin burn injury The skin burn injury over the manikin body for garments is compared in Fig. 7. During nude exposure to hot water spray, second-degree burn

9 Performance of protective clothing upon hot liquid exposure 801 Fig. 6. The garment shape of G11 before and during hot water exposure. developed over the nude body except the face, shoulder, and side arm. It should be noted that there was no sensor on the feet, and the hands were excluded in this study. When garment G1 was exposed to water spray, the arm and upper chest predicted little burn injury. There was no burn generated at head, shoulder, and part of inner side of the rear thigh. In addition, third-degree burn occurred at left upper thigh, right thigh, and pelvis. Garments G2 and G3 showed similar burn injury distribution. The head, shoulder, arm, abdomen, inner side of left calf, and inner side of rear thigh presented a similar burn pattern to G1. However, there was less third-degree burn and the lower back developed less burn injury than G1. Garment G4 provided good protection and there was low percentage burn, mainly over the upper body. The burn injury of G5 was relatively distributed at the lower manikin surface. G6 evenly developed burn injury over the trunk and leg and the total percentage was lower than the other permeable garments. Skin burn distributed over the manikin body covered by G11 was mostly on the torso and pelvis. The chest, abdomen, and back predicted similar burns to those covered by G2, but there was less burn on the leg. Garments G10, G11, and G12 showed similar skin burn pattern, although the sizes gradually increased. The burn injury occurred at the trunk and pelvis except the sides. There was little burn injury developed at the lower back. The front and back of legs also generated skin burn. The results indicated that some areas did not predict any burns. The shoulders did not burn despite having small air gaps, which is possibly due to the horizontal direction of the sensors. This was consistent with the study on the protection of flame resistant garments from flash fire (Mah and Song, 2010). The water spray directly contacted with chest and mid-back, resulting in only a little water being splashed at the upper chest. Therefore, there was no direct water spray at the shoulder, and thus this area did not develop burn injury. However, the neck and back of the head might get burnt due to the water splashes deflected from the water impact at the chest. There was no burn or little burn at the arms that was caused by the water spray method, namely no direct water spray towards the arms. Similarly, the side trunk, without direct contact with water spray, also did not receive burns. Due to the characteristics of body geometry, air layer over the abdomen was

10 802 Y. Lu, G. Song and J. Li Fig. 7. Skin burn injury distributions in different tests.

11 Performance of protective clothing upon hot liquid exposure 803 large. It was demonstrated that this thick air layer prevented burns in this area under exposure to flash fire (Mah and Song, 2010). However, burns occurred at the abdomen covered by G1 G3 and G10 G12. The direct high-pressure water flow compressed the fabric, decreasing the air layer in this region and resulted in water absorption and penetration. Mass transfer has been demonstrated as the critical factor influencing heat transfer to the sensor (Lu et al., 2012a). Similarly, the larger air layer in the lower back and waist regions might decrease the heat transfer to sensors as long as the air layer is not compressed by the water spray and flow. In some garments, reflective tape was attached at the cuff of the sleeve and leg, shoulder, and back, and arranged in the form of an X at the back. It was found that the crossing reflective tape at the back provided extra protection at the lower back covered by G2, G3, and G6. In addition, some pockets such as chest patch pockets with flap, rear patch pockets, and in-seam pockets were included in the garment design. These might have impact on the skin burn distribution. For semipermeable garments G4 and G5, hot water flowed into the unflapped pockets and accumulated, which discharged energy to the sensor, resulting in burn injury. Conclusions Thermal protective performance of protective clothing against hot liquid spray was investigated by spray manikin system in this study. Different clothing systems showed distinct overall performance. The manikin system was proved to be capable of differentiating the selected protective clothing. Minimizing mass transfer was recognized as the critical factor for protection from hot water. The thickness of fabric and design features showed effects on the performance of impermeable and semipermeable clothing. The effect of fabric weight on heat transfer through protective clothing system seems to be minimal. Maintaining a proper air gap between the garment and human body was a critical factor in improving thermal performance. Adding fabric layers could improve thermal protective performance of garments. The size of garment showed effects on thermal protection of permeable garments, but these were not significant. Burn injury mainly occurred at the areas of compression upon water spray, heavy water flow, and small air gap. Reflective tape could provide extra protection. These findings could be helpful to provide a technical basis to fabric engineering and garment design. Authors Note Caution should be taken in drawing conclusions about safety benefits from these results. The data described in this paper are taken from laboratory results and the developed skin burn models. They are not presented to predict actual field conditions. The actual performance provided from the clothing can be quite different given the specific human activity, thermal exposure, and clothing conditions. 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