A. Kurczewska, Central Institute for Labour Protection-National Research Institute, Lodz, Poland.
The materials for constructing “smart” clothing, that is clothing that, on its own, supports thermoregulation processes of the body, has been tested. The concept assumes a multilayer system of materials that cooperates changing its isolation in response to changes of environment and body temperatures. The system consists of electrically-heated material, “active” insulation, and thermoactive membrane. As the first layer, the material with electroconductive yarn has been proposed. There have been tested and compared electrically-heated materials with different electroconductive yarns. The most efficient ones have been selected, put into the multilayer system, and then tested. All the tests have been conducted on apparatus that have been worked out in Central Institute for Labour Protection-National Research Institute.
T. Bernard, C. Ashley, V. Caravello, University of South Florida, Tampa, FL.
The level of heat stress is dictated by environment, metabolic rate, and clothing. The physiological state in response to the heat stress can be seen in heart rate, core temperature, and skin temperature. A convenience set of data was used to examine the ability of physiological state to predict level of heat stress (i.e., compensable vs. uncompensable). The study trials were designed to find the transition point between compensable and uncompensable heat stress as it relates to environment, clothing, and work demands. The individual trials began with a low level of heat stress that allowed a physiological steady-state to be established, and then the environmental contribution was increased in small steps every 5 minutes. The upper limit of compensable heat stress was identified as the critical level of heat stress, and the physiological state noted. The physiological states at 15 min prior to and after the critical level were also noted. The pre-critical and critical levels were compensable heat stress and the post-critical level was uncompensated heat stress. The data set included 1461 observations over gender, 10 clothing ensembles, and 3 levels of metabolic rate. Logistical regression was used to predict the level of heat stress from the independent variables of skin temperature, core temperature, and heart rate along with potential effect modifiers of gender, clothing, and metabolic demands. Significant predictors were heart rate, skin temperature, gender, and metabolic demands. Most of the predictive power was in heart rate, skin temperature, and gender; skin temperature was the single best predictor. The results tentatively point to novel methods of personal monitoring and reporting risk in real time.
V. Caravello, C. Ashley, T. Bernard, University of South Florida, Tampa, FL; E. McCullough, University of Kansas, Wichita, KS.
With regard to heat stress, the limiting factor inherent in clothing ensembles is the total evaporative resistance. For the same work demands, the greater the evaporative resistance of the clothing, the lesser the ability to cool by sweat evaporation and hence the lower the environmental contributors to heat stress, especially water vapor pressure, must be. Knowing the evaporative resistance provides a means to compare candidate ensembles. Further, a value for evaporative resistance means that a rational method, such as the ISO Required Sweat Rate, can be used to assess the heat stress exposure. In this study, the evaporative resistance of five clothing ensembles (cotton work clothes, cotton coveralls, Tyvek 1424, NexGen, and Tychem) was determined empirically from wear tests. The ensembles were configured similarly in that there were no hoods. The humidity was held constant at 50% rh, and three levels of metabolic rate (80, 160, 240 W/m2) were explored. Fifteen heat-acclimated participants (11 men and 4 women) completed trials for all combinations of clothing ensemble and environment. A three-way ANOVA (ensemble, metabolic rate, participants) was used to analyze the data. Significant differences (p<0.0001) among ensembles, metabolic rates, participants, and the interaction between ensembles and metabolic rate was found. As expected, Tychem had the highest resistance at 0.034 kPa m2/W. NexGen was next at 0.027; followed by Tyvek 1424 at 0.026. Coveralls was 0.025, and work clothes was 0.024. Pair-wise comparisons adjusted for multiple comparisons were used to locate the differences among ensembles. Tychem was different from all others and NexGen was different from work clothes. We also found that evaporative resistance decreased with increased metabolic rate. This can be explained by the pumping action associated with increased work.
K. Semeniuk, J. Dionne, A. Makris, Med-Eng Systems Inc., Ottawa, ON, Canada; T. Bernard, C. Ashley, T. Medina, University of South Florida, Tampa, FL.
Liquid and vapor impermeable clothing ensembles are engineered to protect workers exposed to biological and chemical threats. Regrettably, individual health and safety is compromised due to the added risk of heat stress created by these same ensembles. Limited permeability retards the diffusion of water vapor, producing an extremely humid microclimate that prevents sweat evaporation and thus inhibits active cooling and the ability to transfer heat to the surrounding environment. Therefore, personal cooling systems (PCS) should be used with protective ensembles to reduce the effects of physiological and environmental heat stress. The purpose of this research was to compare the performance results of a PCS liquid cooling garment (LCG) worn under various impermeable ensembles, using thermal manikin and physiological test methods. All tests were carried out in environmental chambers at 35°C. In physiological tests, five male subjects exercised at a metabolic rate of approximately 300 W. A sweating thermal manikin, with surface temperature maintained at 35°C, was used to assess performance while accounting for the effective evaporative heat transfer. To compare methods, the rate of heat transfer was calculated by measuring the mass flow rate and the inlet and outlet temperature of the circulating liquid in the LCG. Average heat transfer rates of 330 and 185 W were measured from the manikin and physiological trials, respectively. Additional physiological variables were also used to assess the significance of the LCG. For the no cooling and cooling conditions, the average rates of change in core temperature were found to be 0.019 and 0.009°C/min, respectively, and the average rates of change in heart rate were found to be 0.80 and 0.15 bpm/min, respectively. LCG heat transfer was successfully measured using both thermal manikin and physiological methods, with the latter results being lower due to the body’s thermoregulatory mechanisms and mechanical and metabolic efficiency.
R. Phalen, S. Que Hee, University of California-Los Angeles, Los Angeles, CA.
Decisions regarding the selection of chemical protective gloves are often based on general permeation guidelines. The major assumption is that glove types are equivalent. The aim of this study was to characterize and compare nine types of powder-free, unlined, and unsupported nitrile gloves using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometry to assess suitability for surface infrared analysis of the dicarboximide fungicide Captan. Within glove, between glove, and between lot variabilities were measured for 13 gloves from 5 manufacturers at 740, 1124, 1252, and 1735 cm-1, the characteristic Captan peak wavelengths. Appreciable glove reflectances will limit sensitivity. Relative humidity (RH) and temperature effects on the surfaces of three gloves were evaluated by preconditioning them overnight at 2 ± 1, 31 ± 1, 55 ± 1, 76 ± 2, and 87 ± 4% RH. For all gloves except one (Best, inner), 1735 cm-1 provided the greatest sensitivity. At 1735 cm-1, outer glove absorbances ranged from 0.0074 ± 0.0005 (Microflex) to 0.0195 ± 0.0024 (Safeskin). Average within glove coefficients of variation (CVs) ranged from 2.7 (Best, range 0.9–5.3%) to 10% (Safeskin, 1.2-17%). Within glove CVs greater than 10% were for one brand (Safeskin). Between glove CVs ranged from 2.8 (Best) to 28% (Safeskin). Between lot variation was statistically significant (p<0.05) for all lots tested (Best, Microflex, and Safeskin). RH had variable effects dependent on brand and wavelengths. For two gloves (Ansell and Microflex), absorbances at 740 cm-1 and 3430 cm-1 (-OH stretching) increased significantly (p<0.05) with increasing RH. Overall, substantial within glove, between glove, and between lot variabilities were observed. ATR-FTIR is a rugged analytical tool for measuring glove surface reflectance, detecting surface humidity effects, and choosing selective and sensitive wavelengths for infrared analysis of nonvolatile surface contaminants.
P. Gao, B. Tomasovic, NIOSH, Pittsburgh, PA; J. Wassell, NIOSH, Morgantown, WV.
The purpose of this study was to investigate the change in tensile properties of neoprene and nitrile gloves after repeated exposure to acetone and thermal decontamination. Neoprene (Stanzoil N-440) and nitrile synthetic rubber (Ansell Edmont 37-155) gloves were cut into circular swatches with a diameter of about 18 cm. Thicknesses of the swatches were measured in five places and the mean thickness was calculated. Each swatch was mounted at the base of a cylinder-like exposure chamber. Neat 99.7% acetone was poured onto the outer glove surface and the contact continued until steady-state permeation was fully established. The chamber was then disassembled and the swatch was air dried inside a fume hood for about 3 hours followed by thermal decontamination at 100°C for 16 hours using an incubator. Dumbbell-shaped samples were punched from the exposed swatches using an Arbor Press. The tensile strength and ultimate elongation of these samples were measured according to the ASTM D412 Method using the Lloyd Material Testing Instrument. The exposure/decontamination procedure was repeated for a maximum of 10 cycles.
Results from each exposure/decontamination cycle were compared with those obtained for the new glove materials. For neoprene exposed to acetone, the mean tensile strength for the new swatches was 15.0 MPa. The tensile strength consistently decreased to 8.8 MPa after nine exposure/decontamination cycles. Multiple comparisons indicated that the mean tensile strengths between the new swatches and each exposure/decontamination group were significantly different (P ≤ 0.05). For nitrile exposed to acetone, the mean tensile strength for the new swatches, 37.1 MPa, remained virtually unchanged, 36.0 MPa after nine exposure/ decontamination cycles (P ≥ 0.05). Similar tendencies were observed for the ultimate elongation measurements. These results indicate that exposure to acetone and/or thermal decontamination might degrade neoprene gloves but not nitrile gloves.
K. Chapman, K&M Environmental Inc., Virginia Beach, VA; E. DeMedeiros, J. Vincent, North Safety Products, Cranston, RI.
Historically, the only allowed method for respiratory protection against toluene diisocyanate (TDI) exposure in the workplace has been the use of supplied air. According to the Code of Federal Regulations, 29 CFR 1910.134, “for protection against gases and vapors, the employer shall provide: (A) an atmosphere-supplying respirator, or (B) an air purifying respirator, provided that: (1) the respirator is equipped with an end-of-service-life indicator (ESLI) certified by NIOSH for the contaminant; or (2) if there is no ESLI appropriate for conditions in the employer’s workplace, the employer implements a change schedule for canisters and cartridges that is based on objective information or data that will ensure that canisters and cartridges are changed before the end of their service life.” Estimating the service life and preparing cartridge change schedules requires data, which is, often times, unknown or difficult to determine. To eliminate the need for cumbersome change schedules and simplify user training, an ESLI for TDI has been developed that is inside the gas and vapor cartridge to give workers a real-time indication of cartridge service life. The ESLI is a chemical sensor specific to TDI that is inside the clear respirator cartridge. It undergoes a color change from white to red when exposed to TDI indicating that the service life of the cartridge has expired.
This organic vapor cartridge with an ESLI specific for TDI has met the requirements for approval from NIOSH. Seven NIOSH tests were performed, including three cartridges tested as received, two cartridges equilibrated at high humidity (85% RH), and two cartridges equilibrated at low humidity (25% RH). The organic vapor cartridge was tested against TDI at 5ppm, 50% RH, 25°C, and 32 L/min per cartridge. Additionally, shelf-life and service life testing was also performed.
A. Hartkopf, Ansell Healthcare, Red Bank, NJ; N. Schlatter, F. Crouso, Ansell Healthcare, Coshocton, OH.
As chemical processes become more automated, and lab work continues to evolve toward use of smaller quantities of chemicals, glove protection requirements are moving away from immersion or even intermittent contact protection and toward simple splash protection. Although test results from ASTM F739 and F1383 can be used as the basis for recommending gloves for splash protection, there is a clear need for a new approach. When a chemical falls on a glove, two phenomena begin—evaporation from the outside surface and diffusion/ degradation toward the inside surface. Evaporation rate is related to volatility; ASTM F739 continuous contact breakthrough times can provide a rough indication of diffusion rate. A newer test, ASTM F1383, measures breakthrough time for a series of simulated splashes under conditions of forced evaporation; F1383 breakthrough times thus reflect both volatility and permeation. The F1383/F739 breakthrough time ratio correlates very roughly with boiling point for a series of chemicals tested against the same glove material. It is thus possible to develop a more broadly applicable splash rating system that combines boiling point and F739 breakthrough time data with a toxicity rating for the chemical of interest. We have used these concepts to formulate splash ratings for a wide range of thin disposable gloves, as well as a selected number of thicker ones.
A. Hartkopf, Ansell Healthcare, Red Bank, NJ; D. Albery, F. Crouso, Ansell Healthcare, Coshocton, OH.
Replacing the challenge liquid half of a standard ASTM F739 test cell with a glass cylinder allows one to carry out two new types of chemical resistance test. Permeation breakthrough is monitored in the usual manner, either with flowing gas/FID or with flowing water/pH detection.
1. True splash tests, as opposed to the intermittent contact test described in ASTM F1383. With a motorized pipet, 50 ul of challenge chemical is deposited on the test specimen and breakthrough time is measured. The size of the “splash” can be varied as desired, and/or several successive “splashes” can be deposited with a constant time interval between them. Also, the orientation of the test cell can be varied from horizontal to vertical, and can be static or dynamic. For consistency and simplicity we hold the cell with the test specimen at a 45 degree angle and eject the “splash” onto the center of the specimen; the liquid runs down to the side of the cell to the PTFE gasket and it continues to permeate and/or evaporate. Breakthrough times are indicated by a peak in the FID signal or a spike in the pH. In either case the “splash breakthrough time” parallels the standard F739 breakthrough time. This procedure is useful in cases where the liquid is especially hazardous, or when only a limited amount is available.
2. Conventional F739 tests with highly viscous or liquids or malleable solids. A common variation of the latter type of sample is a two-component adhesive or hardening polymer system. We have tested both types, focusing on permeation of residual solvent in an adhesive system and permeation of methyl methacrylate in bone cement. In cases where the concentration of a potentially permeating compound is relatively low (residual solvents) there is usually no detectable breakthrough.
Posted May 30, 2004