Evaluation of protective ensemble thermal characteristics through sweating hot plate, sweating thermal manikin, and human tests.

The purpose of this study was to evaluate the predictive capability of fabric Total Heat Loss (THL) values on thermal stress that Personal Protective Equipment (PPE) ensemble wearers may encounter while performing work. A series of three tests, consisting of the Sweating Hot Plate (SHP) test on two sample fabrics and the Sweating Thermal Manikin (STM) and human performance tests on two single-layer encapsulating ensembles (fabric/ensemble A = low THL and B = high THL), was conducted to compare THL values between SHP and STM methods along with human thermophysiological responses to wearing the ensembles. In human testing, ten male subjects performed a treadmill exercise at 4.8 km and 3% incline for 60 min in two environmental conditions (mild = 22°C, 50% relative humidity (RH) and hot/humid = 35°C, 65% RH). The thermal and evaporative resistances were significantly higher on a fabric level as measured in the SHP test than on the ensemble level as measured in the STM test. Consequently the THL values were also significantly different for both fabric types (SHP vs. STM: 191.3 vs. 81.5 W/m(2) in fabric/ensemble A, and 909.3 vs. 149.9 W/m(2) in fabric/ensemble B (p < 0.001). Body temperature and heart rate response between ensembles A and B were consistently different in both environmental conditions (p < 0.001), which is attributed to significantly higher sweat evaporation in ensemble B than in A (p < 0.05), despite a greater sweat production in ensemble A (p < 0.001) in both environmental conditions. Further, elevation of microclimate temperature (p < 0.001) and humidity (p < 0.01) was significantly greater in ensemble A than in B. It was concluded that: (1) SHP test determined THL values are significantly different from the actual THL potential of the PPE ensemble tested on STM, (2) physiological benefits from wearing a more breathable PPE ensemble may not be feasible with incremental THL values (SHP test) less than approximately 150-200 W·m(2), and (3) the effects of thermal environments on a level of heat stress in PPE ensemble wearers are greater than ensemble thermal characteristics.

Physiological responses to wearing a prototype firefighter ensemble compared with a standard ensemble.

This study investigated the physiological responses to wearing a standard firefighter ensemble (SE) and a prototype ensemble (PE) modified from the SE that contained additional features, such as magnetic ring enclosures at the glove-sleeve interface, integrated boot-pant interface, integrated hood-SCBA facepiece interface, and a novel hose arrangement that rerouted self-contained breathing apparatus (SCBA) exhaust gases back into the upper portion of the jacket. Although the features of the PE increased the level of encapsulation of the wearer that could lead to increased physiological stress compared with the SE, it was hypothesized that the rerouted exhaust gases provided by the PE hose assembly would (1) provide convective cooling to the upper torso, (2) reduce the thermal stress experienced by the wearer, and (3) reduce the overall physiological stress imposed by the PE such that it would be either less or not significantly different from the SE. Ten subjects (seven male, three female) performed treadmill exercise in an environmental chamber (22°C, 50% RH) at 50% [image omitted]O(2max) while wearing either the SE with an SCBA or the PE with an SCBA either with or without the hose attached (designated PEWH and PENH, respectively). Heart rate (HR), rectal and intestinal temperatures (T(re), T(in)), sweat loss, and endurance time were measured. All subjects completed at least 20 min of treadmill exercise during the testing. At the end of exercise, there was no difference in T(re) (p = 0.45) or T(in) (p = 0.42), HR, or total sweat loss between the SE and either PEWH or PENH (p = 0.59). However, T(sk) was greater in PEWH and PENH compared with SE (p < 0.05). Total endurance time in SE was greater than in either PEWH or PENH (p < 0.05). Thus, it was concluded that the rerouting of exhaust gases to the jacket did not provide significant convective cooling or reduce thermal stress compared with the SE under the mild conditions selected, and the data did not support the hypotheses of the present study.

Evaluation of nano- and submicron particle penetration through ten nonwoven fabrics using a wind-driven approach.

Existing face mask and respirator test methods draw particles through materials under vacuum to measure particle penetration. However, these filtration-based methods may not simulate conditions under which protective clothing operates in the workplace, where airborne particles are primarily driven by wind and other factors instead of being limited to a downstream vacuum. This study was focused on the design and characterization of a method simulating typical wind-driven conditions for evaluating the performance of materials used in the construction of protective clothing. Ten nonwoven fabrics were selected, and physical properties including fiber diameter, fabric thickness, air permeability, porosity, pore volume, and pore size were determined. Each fabric was sealed flat across the wide opening of a cone-shaped penetration cell that was then housed in a recirculation aerosol wind tunnel. The flow rate naturally driven by wind through the fabric was measured, and the sampling flow rate of the Scanning Mobility Particle Sizer used to measure the downstream particle size distribution and concentrations was then adjusted to minimize filtration effects. Particle penetration levels were measured under different face velocities by the wind-driven method and compared with a filtration-based method using the TSI 3160 automated filter tester. The experimental results show that particle penetration increased with increasing face velocity, and penetration also increased with increasing particle size up to about 300 to 500 nm. Penetrations measured by the wind-driven method were lower than those obtained with the filtration method for most of the fabrics selected, and the relative penetration performances of the fabrics were very different due to the vastly different pore structures.