Protective Ensembles Research Articles

Benefit of heat acclimation is limited by the evaporative potential when wearing chemical protective clothing

Heat acclimation-induced sweating responses have the potential of reducing heat strain for chemical protective garment wearers. However, this potential benefit is strongly affected by the properties of the garment. If the clothing ensemble permits sufficient evaporative heat dissipation, then heat acclimation becomes helpful in reducing heat strain. On the other hand, if the garment creates an impenetrable barrier to moisture, no benefit can be gained from heat acclimation as the additional sweating cannot be evaporated. Ten subjects were studied exercising on a treadmill while wearing two different chemical protective ensembles. Skin heat flux, skin temperature, core temperature, metabolic heat production and heart rate were measured. It was found that the benefit of heat acclimation is strongly dependent on the ability of the body to dissipate an adequate amount of heat evaporatively. The evaporative potential (EP), a measure of thermal insulation modified by moisture permeability, of the clothing ensemble offers a quantitative index useful to determine, a priori, whether heat acclimation would be helpful when wearing protective clothing system. The data show that when EP is <15%, heat acclimation affords no benefit. An evaporative potential graph is created to aid in this determination.

A thermal physiological comparison of two HAZMAT protective ensembles with and without active convective cooling.

Wearing impermeable garments for hazardous materials (HAZMAT) cleanup can often present a health and safety problem for the wearer. Even short duration cleanup activities can produce heat-stress injuries in HAZMAT workers. It was hypothesized that an internal cooling system might increase worker productivity and decrease the likelihood of heat-stress injuries in typical HAZMAT operations. Two HAZMAT protective ensembles were compared during subjects' treadmill exercise. The different ensembles were created using two different suits: a Trelleborg vapor protective suit representative of current HAZMAT suits and a prototype suit developed by engineers at the National Aeronautics and Space Administration (NASA). The two life-support systems used were a current-technology Interspiro Spirolite breathing apparatus and a liquid air breathing system that also provided convective cooling. Twelve local members of a HAZMAT team served as test subjects. They were fully instrumented to allow a complete physiological comparison of their theramal responses to the different ensembles. Results showed that cooling from the liquid air system significantly decreased thermal stress. The results of the subjective evaluations of new design features in the prototype suit were also highly favorable. Incorporation of these new design features could lead to significant operational advantages in the future.

Case Study

ABSTRACT In agriculture, hydrogen cyanamide is used as a growth regulator for uniform bud break in crops including peaches, kiwis, and grapes. In experimental animals and volunteer human subjects, cyana-mide has been shown to suppress ethanol consumption and has been used in place of disulfiram for the treatment of alcoholism. Typically, illness with cyanamide has been associated with an antabuse reaction when used with alcohol. However, an intoxication syndrome to cyana-mide has been also described in industry and agriculture. The worker in this study experienced hypotension, vertigo, nausea, and puffiness of the face without exposure to alcohol while applying hydrogen cyanamide for use as a growth regulator in kiwi fruit. He was wearing a full protective ensemble and there was no patient history or objective signs of alcohol use. The hypotension was without tachycardia and lasted four days after exposure. This case suggests that an acute intoxication syndrome from the use of hydrogen cyanamide includes hypotension without tachycardia, nausea and vertigo at the onset. The difficulty of obtaining an accurate history is highlighted.

Effects of Chemical Protective Clothing on Military Performance: A Review of the Issues

This review in this special issue of Military Psychology on the effects of chemical protective clothing (CPC) on military performance provides a historical perspective on continued anxieties over likely use of battlefield chemical–biological weapons and summarizes significant concerns of military personnel wearing CPC in training and combat. This review describes psychophysiological stresses such protective ensembles have on personnel and how these affect military performance, and it summarizes major military psychological research programs on the effects of wearing CPC. This article reviews what is known about wearing CPC, describes future CPC developments, and identifies domains for improved military training with CPC.

The Impact of Chemical Protective Clothing on Military Operational Performance

Wearing chemical protective clothing (CPC) while conducting military operations limits a soldier's dexterity, mobility, command and control, communications, and endurance. A series of field studies was conducted to identify mission degradations from the protective clothing on the chemically contaminated battlefield. The studies differed in complexity but had a common goal of comparing task performance and endurance of soldiers wearing the full protective ensemble versus wearing the standard military field uniform. This article summarizes 3 U.S. Army programs. One of them is called the Physiological and Psychological Effects of the NBC Environment and Sustained Operations on Systems in Combat. A review of 19 studies concerning combat, combat support, and combat service support systems shows that most military tasks can be performed satisfactorily while CPC is worn, but usually, extra time is required to perform such tasks. Higher ambient temperatures and high workloads are especially detrimental to endurance. Realistic training in the ensemble is deemed essential for sustaining performance on the chemically contaminated battlefield.

Analysis and Design of an Air-Cycle Microclimate Cooling Device

This paper presents an innovative concept of using air-cycle technology for the development of a microclimate cooling device for use by soldiers in the battlefield. The device is an integrated heat engine and heat pump which supplies air at a prescribed temperature and humidity for personal cooling of a soldier wearing protective ensembles, generates electrical energy to power communication equipment, and produces drinking water by condensing atmospheric moisture which may be very useful in desert warfare. It consists of a centrifugal compressor, two turbines or expanders, a combustion chamber, three heat exchangers, a water separator, and an electric generator. Atmospheric air is used as the working fluid in both the engine and cooling loops and diesel is used as the fuel for combustion. A detailed thermodynamic analysis and design optimization was performed. It was found that the system efficiency increases with operating pressure ratio, attains a maximum, and decreases with further increase of pressure ratio. The system efficiency was found to be also dependent on the air-fuel ratio, and the maximum efficiency was found to occur at a specific air-fuel ratio, for any given pressure ratio. The optimum operating condition determined from the thermodynamic analysis was used to outline a detailed design of the system.

The Relationship between Cognitive Performance and Stress Perceptions in Military Operations

The study reported here is part of a continuing research program investigating the links between psychological stress responses and performance in a variety of settings. A battery of psychological and cognitive measures designed to assess stress perceptions, coping resources, and cognitive performance was administered at selected times in association with the daily test activities of smoke and decontamination platoon operations. During testing soldiers wore the full chemical protective ensemble including mask (MOPP IV). Canonical correlation analyses were computed to examine the relationship between the stress perception measures (predictor variables) and cognitive performance measures (outcome variables). The direction of the results indicates that as subjects experience an increase in their perception of the situation as stressful their corresponding performance declines. These results are consistent with the literature and indicate that the stress perception measures and performance measures used in this study are sensitive indicators of stress.

Intermittent microclimate cooling during rest increases work capacity and reduces heat stress.

Requirements for special protective equipment while working in hazardous environments can present a significantly increased thermal burden and early onset of physical fatigue. Ambulatory (backpack) or tethered personal cooling can accelerate metabolic heat removal, but is often not practical from an ergonomic standpoint. The efficacy of incorporating personal cooling during non-ambulatory rest periods was evaluated in subjects (n = 8) with varying levels of fitness. Treadmill work (approximately 475 W, 40% VO2 max) was alternately performed for 30 min followed by 30 min of rest. Subjects walked and rested under three separate experimental conditions: (1) control (C), in which light clothing was worn; (2) CPE, in which a chemical protective ensemble (CPE) was worn, and (3) CPE plus intermittent microclimate cooling (COOL). The WBGT condition for all trials was 31 degrees C. During the COOL trial the subjects additionally wore a personal cooling vest which allowed for the circulation of chilled liquid over the torso during rest. Under C conditions, relatively modest changes in rectal temperature (Tre) were observed, which stabilized over time. CPE wear resulted in a progressive rise in Tre and early fatigue. The addition of intermittent cooling during each rest cycle (COOL trial) significantly attenuated heat storage such that an oscillating, but equilibrated Tre was established and work capacity was at least doubled. Moreover, the perceived cooling effect was appreciable for all subjects. Therefore, intermittent personal cooling provided a useful means of enhancing work productivity and may have application for certain military and industrial personnel performing heavy work in hot environments. This approach should provide a practical alternative for reducing stress/fatigue when work/rest cycles are employed.

The extinguishment of fires using low flow water hose streams?part II

Fire extinguishment tests were conducted in a simulated shipboard space. Portable extinguishers, a low flow water hose reel system, and 3.8 cm diameter water hand lines were used to extinguish the fires. Various protective ensembles were used by the fire fighters, ranging from minimum protection to full protection. Personnel with both a limited and high degree of fire fighting experience were used. Response time was influenced by visibility and the fire fighters' knowledge of the compartment. The low flow water hose reel system was found to be an effective and efficient quick response fire fighting tool. Efficiency, in terms of total water used, was better with the hose reel system compared to the larger, higher flow water hand lines.

Impact of a chemical protective ensemble on cognitive and psychomotor performance : Kaufman, J.W., Dejneka, K.Y., Morrissey, S.J., and Bittner, A.C. In: B. Das (Ed), Advances in industrial ergonomics and safety — II, Taylor & Francis, London, 1990, pp 905–912, 12 refs

Impact of a chemical protective ensemble on cognitive and psychomotor performance : Kaufman, J.W., Dejneka, K.Y., Morrissey, S.J., and Bittner, A.C. In: B. Das (Ed), Advances in industrial ergonomics and safety — II, Taylor & Francis, London, 1990, pp 905–912, 12 refs

Nutrient, Waste Management, and Hygiene Systems for Chemical Protective Suits

Current United States military chemical protective ensembles do not provide for feeding, removing body wastes, or ensuring the hygiene of troops operating in a contaminated environment. As part of a nuclear-biological-chemical life support demonstration program, systems were developed to provide these capabilities. The nutrient system consisted of foods packaged in tube dispensers and a delivery system compatible with North Atlantic Treaty Organization respirators. The waste management/hygiene systems consisted of waste collection and hygiene items incorporated into a retractable-arm suit design with integrated airlock. A field demonstration of the systems resulted in successful use by armored vehicle personnel, high, positive user feedback, and only minor functional problems.

Restriction to movement in fire-fighter protective clothing: evaluation of alternative sleeves and liners

The purpose of this study was to evaluate alternative designs and liner configurations in fire-fighter protective clothing, or ‘turnout gear’, to determine the restriction to wearer movement imposed by each. The independent variables were: (1) two alternative sleeve designs (i e, a ‘traditional’ sleeve design and a prototype sleeve design, featuring additional gusset width and altered armseye position) plus a station uniform worm without any protective clothing and/or equipment; (2) three liner configuration variations (i e, a ‘traditional’ liner configuration, incorporation of one additional liner, and incorporation of two additional liners); and (3) wearing or not wearing an SCBA (self-contained breathing apparatus). The dependent variables for this study were: (1) range of movement in four upper body joints; and (2) a semantic differential scale to evaluate wearers' subjective evaluation of each protective ensemble. Nine male subjects were used. For each of the four joint movements measured (i e, shoulder flexion/extension, shoulder adduction/abduction, shoulder rotation, elbow flexion/extension), a Leighton Flexometer ∽ was strapped to the subject at the appropriate body location. The subject was instructed to take the body position indicated. A reading was taken, then the subject was asked to move the body segment to the fullest extent possible in the direction indicated by the researcher. A second reading (representing range of movement) was taken. This procedure was repeated three times for each movement. After the test, subjects were instructed to fill out a semantic differential scale which described their subjective evaluations of the clothing/ equipment configuration. Results showed greater wearer range of movement in the elbow area for the prototype sleeve design over the more traditional sleeve design. Incorporation of additional liners resulted in higher wearer acceptability for the turnout coats than when these liners were not used. As expected, use of an SCBA was extremely restrictive to mobility, and made the protective ensemble less acceptable to wearers.

Effects of thermal environment and chemical protective clothing on work tolerance, physiological responses, and subjective ratings

This study examined the physiological and subjective responses of nine healthy men who performed work while wearing two types of protective ensembles in each of three thermal environments. The subjects, all experienced with the use of protective ensembles, each performed low intensity treadmill exercise (23% of VO2 max while not wearing a Self-Contained Breathing Apparatus [SCBA] or protective clothing) under six experimental conditions: two ensembles (SCBA--light work clothing and SCBA; and CHEM--a two-piece chemical protective ensemble with SCBA) during exposure to 'cool' (10.6 degrees C/water vapour pressure [Pw] 0.76 kPa), 'neutral' (22.6 degrees C/Pw 1.52 kPa), and 'hot' (34 degrees C/Pw 2.90 kPa) environments. Each test was intended to continue for 120 min; however the duration and number of work/rest periods within the testing session varied according to the specific responses of each individual. At the completion of each test seven subjective responses were recorded. Physiological data, collected every minute during each test, included heart rate, and skin and rectal temperature. The total worktime was significantly shorter in the hot environment while wearing the CHEM ensemble (53.4 min) compared to all the other conditions (103-105 min). The mean maximum physiological values also indicated significant differences due to thermal environment and/or ensemble. Work performance did not appear to be limited in a cold environment with either ensemble tested. The physiological responses to working in the CHEM/neutral condition were very similar to those occurring in a hot environment wearing the SCBA ensemble. The subjective responses also indicated significant differences due to thermal environment and ensemble, with subjects perceiving the CHEM ensemble as less favourable than the SCBA ensemble. The results suggested that, even at a low work intensity, individuals wearing chemical protective clothing in the heat will require progressively shorter work periods, and more frequent and longer rest periods.

Infrared Thermometry in the Measurement of Heat Stress in Firefighters Wearing Protective Clothing

Abstract This study investigated the performance of a new infrared-sensing thermometer in the determination of heat stress in firefighters performing moderate exercise in two protective clothing ensembles. All existing consensus standards approach the topic of heat stress monitoring and prevention. These standards are designed to keep the core body temperature of workers below 38°C. Direct measurement of rectal temperature is inconvenient and impractical, so surrogate measures of environmental heat have been widely accepted. Surrogate measures are poor predictors of heat stress in situations where protective clothing interferes with the body's means of losing heat. In these situations, direct measurement of the body's response to heat is desirable. Previous investigation had shown the effectiveness of infrared thermometry in a surgical setting, but no research had been done in the area of worker monitoring. Eight hazardous materials-trained firefighters exercised on a stair machine while wearing gym cloth...

Sustained Operations of Artillery Crews in NBC and non-NBC Environments

The capability of artillery crews to perform fire missions was studied as a function of sustained time on the task and clothing condition. Crews wearing either the standard Army field duty uniform (BDU) or a chemical protective ensemble (MOPP gear) attempted to conduct missions for up to 24 hours. Each of three MOPP crews were able to perform for only a limited time (about 2 hours), primarily because they had problems working in a hot environment (approximately 90 degrees F). A BDU crew completed its scenario, which was conducted under similar environmental conditions. Times to fire rounds were much greater in the MOPP crews than the BDU crew, exemplifying the performance difficulties associated with wearing a bulky, restrictive ensemble that can degrade important skills and functions.

Safety Topics

RECENT discussion has focussed on the protection of military aircrew from the rigours of operating high performance, agile aircraft while at the same time expecting high mental and physical performance to meet the operational requirements of a mission. The cockpit space, seat design and availability of controls must optimise the room available and the complete protective clothing ensemble must provide free movement and not compromise effectiveness.

Performance Standards for Improving Chemical Protective Suits

This paper describes the basis and requirements of various standards for the manufacture of chemical protective suits currently under development by the Ameri can Society for Testing and Materials (ASTM) and the National Fire Protection Association (NFPA). Standards of both groups are aimed at improving product doc umentation to allow end users to have better information for selecting chemical pro tective suits for their respective applications. NFPA standards will also establish minimum performance requirements judged necessary to provide acceptable levels of protection for end users involved in hazardous chemical response and operations. These standards cover the full range of chemical protective suits ranging from dis posable coveralls to totally-encapsulating protective ensembles. Documentation and performance requirements apply to suit materials and components as well as to the total suit. ASTM and NFPA expect to complete and promulgate each of the standards by late 1989

Heat strain and heat stress for workers wearing protective suits at a hazardous waste site.

In order to evaluate the effects of heat stress when full body protective suits are worn, heart rates, oral temperatures and environmental parameters were measured for five unacclimatized male workers (25-33 years of age) who performed sampling activities during hazardous waste clean-up operations. The protective ensembles included laminated PVC-Tyvec chemical resistant hood suits with rubber boots, gloves full facepiece dual cartridge respirators and hard hats. For comparison, measurements also were performed when the men worked at a similar level of activity while they wore ordinary work clothes. A comparison of the heart rates for the men working with and without suits indicated that wearing the suits imposed a heat stress equivalent to adding 6 degrees to 11 degrees C (11 degrees to 20 degrees F) to the ambient WBGT index. A similar result was obtained by calculating the WBGT in the microclimate inside the suits and comparing it to the ambient WBGT. These results indicate the following: 1) there exists a significant risk of heat injury during hazardous waste work when full body protective clothing is worn, and 2) threshold limit values for heat stress established by the ACGIH must be lowered substantially before extending them to cover workers under these conditions.

Heat Strain and Heat Stress for Workers Wearing Protective Suits at a Hazardous Waste Site

In order to evaluate the effects of heat stress when full body protective suits are worn, heart rates, oral temperatures and environmental parameters were measured for five unacclimatized male workers (25–33 years of age) who performed sampling activities during hazardous waste clean-up operations. The protective ensembles included laminated PVC-Tyvec chemical resistant hood suits with rubber boots, gloves, full facepiece dual cartridge respirators and hard hats. For comparison, measurements also were performed when the men worked at a similar level of activity while they wore ordinary work clothes. A comparison of the heart rates for the men working with and without suits indicated that wearing the suits imposed a heat stress equivalent to adding 6° to 11°C (11° to 20°F) to the ambient WBGT index. A similar result was obtained by calculating the WBGT in the microclimate inside the suits and comparing it to the ambient WBGT. These results indicate the following: 1) there exists a significant risk of heat injury durihg hazardous waste work when full body protective clothing is worn, and 2) threshold limit values for heat stress established by the ACGIH must be lowered substantially before extending them to cover workers under these conditions.

Impact of the Chemical Protective Ensemble on the Performance of Basic Medical Tasks

The purposes of this study were to measure the ability of medical specialists to perform eight selected basic medical tasks while in fatigue uniform, MOPP-4, or MOPP with a tactile glove prototype, to measure learning effects on performance of these tasks, to determine the degree to which task performance is degraded by MOPP-4 with or without the prototype gloves, and to obtain preliminary durability and user satisfaction data on tactile glove. The present findings indicate that soldiers must practice specific tasks when wearing the chemical protective ensemble if they are to develop the skills needed to function on the integrated battlefield.