Comparison between required clothing insulation and that actually worn by workers exposed to artificial cold

Required Clothing Insulation (IREQ) is a new thermal index submitted to the International Organisation for Standardisation (ISO) for discussion. It is designed to prevent general body cooling and is based on an analysis of heat exchanges. The thermal clothing insulation actually worn (lcl) is estimated using a new method, also submitted to ISO.

IREQ of 54 workers exposed to artificial cold (air temperature between −30° C and +10° C) was compared with lcl actually worn by these workers. The results of the present study show that, on average, the workers choose accurately lcl they need if their IREQ is below and up to 1·5 clo. Moreover, these workers prefer to wear garments which provide them with thermal comfort. If IREQ of workers is higher than 1·5–2 clo (i e, workers exposed to −20° C), it is difficult for them to increase their thermal insulation with additional garments. Although their lcl is not sufficient, there is no risk of gradual body cooling because of their continuous time exposure (CTE) which is shorter than the calculated Duration Limited Exposure (DLE). On the other hand, Wind Chill Index (WCI), which is proposed to prevent local cooling, is better adapted to prevent cold injuries than physiological thermal strain; for example, impairment of manual dexterity cannot be prevented with this index.     

Change in contact temperature of finger touching on cold surfaces

This study deals with human fingers touching cold surfaces of four materials (aluminium, steel, nylon and wood) at different surface temperatures (−20°C, −15°C, −10°C, −4°C, 0°C and 2°C). Contact finger skin-surface interface temperature and subjective responses on thermal and pain sensations were determined during touching. Type of material and their surface temperature clearly affected the contact cooling of the finger. Individual variation in finger contact cooling was significant. Contact temperature limits for human fingers touching cold surfaces are suggested according to the experimental results. In addition, time to reach a critical temperature (7°C, 5°C or 0°C) when contacting a cold metallic surface is discussed.

Relevance to industry

The outcome of this experimental study supplies as a basis for the development of an ergonomics database to determine temperature limit values for cold touchable surfaces. The critical temperatures are relevant to all industries where cold surfaces cause a risk of finger contact cooling for the manual protection in the cold operations.     

PREDICTOL: a computer program to determine the thermophysiological duration limited exposures in various climatic conditions

PREDICTOL is a PC program used to determine the thermophysiological duration limited exposures (DLE) in humans, nude or clothed, submitted to various climatic conditions (hot and cold climates) at rest or during a physical exercise. DLE are determined following different standards of the International Standardization Organization (ISO), especially ISO 7933 for hot environment and ISO-TR 11079 for cold environment. The original aspect of this program is that it can be used whatever the climatic conditions. The program presents two modes: an educational interactive mode and a scenario mode. The educational interactive mode demonstrates the thermophysiological effects, expressed as DLE, of different parameter changes (temperature, humidity, wind speed, metabolic heat production by physical exercise, clothing insulation and water vapor permeability). The scenario mode determines DLE for given various linked sequences as encountered in occupational, military or even recreational activities, each sequence being characterized by its climatic conditions, physical activities performed and by physical clothing properties. DLE given by PREDICTOL are correlated to those obtained in various controlled climatic laboratory conditions (r = 0.86; P < 0.001). PREDICTOL is written in Visual Basic 6.0. A "help menu" is provided to explain the use of the program and give information concerning the equations used to calculate both the thermal balance and DLE.     

Effects of repeated exposures to severely cold environments on thermal responses of humans

Abstract

This study was conducted to investigate the effects of different exposure rates on thermal responses with the total cold exposure time the same under each of the conditions. After resting in a warm room (25°C) for 10 minutes, six male students wearing standard cold protective clothing entered an adjoining cold room (— 25°C). Each 5-, 10- and 20-minute cold exposure was repeated 12, 6 and 3 times, respectively. Each cold exposure was followed by a similar duration of rest at 25°C. Total cold exposure time was the same under the three conditions. Rectal temperature, skin temperatures, blood pressure, 17-hydroxycoyticoids (OHCS), counting task and subjective responses were measured. At the end of the cold exposure skin temperatures in the shorter exposures were higher than those in the other conditions, except on the foot. Discomfort due to cold was less in the shorter exposures and manifestation of discomfort was delayed. However, there were no differences among the three conditions in the fall of rectal temperature and urinary excretion of 17-OHCS, which are good indices of cold stress, Moreover, increase in blood pressure and decrease in counting task due to cold were not different among the three conditions. Even though the cold exposure time for each stay was short, when cold exposures were repeated frequently, cold stress of the whole body and decrease in manual task performance were the same as in the longer cold exposure.     

Driving performance in cold, warm, and thermoneutral environments

Driving performance deteriorates at high ambient temperatures. Less is known about the effect of low ambient temperatures and the role of subjective aspects like thermal comfort and having control over the ambient temperature. Therefore, an experiment was constructed in which 50 subjects performed a road-tracking task in a cold (5°C), a thermoneutral (20°C) or a warm (35°C) climate. All subjects had a heater/blower (H/B) which generated a fixed amount of heat/wind that could either be controlled or not controlled.

In the cold climate, averaged leg skin temperature dropped to 18.5°C and head skin temperature to 24.9°C; the thermal comfort was rated between ‘cold’ and ‘very cold’. In the warm climate, averaged leg skin temperature rose to 36.6°C and head skin temperature to 30.8°C; the thermal comfort was rated as ‘hot’. Driving performance in the ambient temperature extremes decreased 16% in the cold environment and 13% in the warm situation.

Having control over the local head temperature by adjusting a H/B affected neither thermal comfort nor driving performance. In agreement with the literature on priming effects, subjects who started with the no-control condition performed much better in all driving tasks because they were primed to focus on the driving task as such, rather than the complex combination of temperature controls and driving task.

It can be concluded that a thermoneutral temperature in a car enhances driving performance and may thus positively affect safety. Using manual climatic controls in hot or cold cars may interfere with the driving task.     

Estimating average daytime and daily temperature profiles within Europe

We present a methodology for estimating the average profiles of daytime and daily ambient temperature from a spatially-continuous database for any location within Europe. The primary database with 1-km grid resolution was developed by interpolation of monthly averages of 7 daily values of temperature: minimum and maximum and 5 measurements at 3-h intervals from 6:00 to 18:00 hours Greenwich Mean Time. With a little over 800 meteorological stations available, we obtained a cross-validation root mean square error of 1.0–1.2 °C, while the interpolation error is lower, at 0.5–0.7 °C.A polynomial fit was applied to estimate the daytime temperature profile (assuming only time from sunrise to sunset) from the interpolated 3-h measurements for each month. The curve fit coefficients make it possible to calculate a number of derived data, such as average daytime temperature, maximum daytime temperature and time of its occurrence within the region. An example demonstrates the coupling of the simulated daytime temperature profile with a model for assessing the relative efficiency of electricity generation by crystalline silicon photovoltaic modules.As an alternative to the polynomial fitting, a double-cosine method was applied to enable calculation of daily (24-h) temperature profiles for each month using interpolated minimum and maximum temperatures. Compared to the polynomial curve-fitting, this method does not offer lower errors, but it provides data which are more suitable for estimation of solar thermal heating or calculation of degree days for building heating/cooling.     

A timeline for hand function following exposure to 2 °C water

In some regions of the North Atlantic Ocean water temperatures are close to 0 °C for half of the year. Individuals who work in this extremely cold water environment will experience hand temperatures that are associated with reduced hand function (e.g. < 8 °C). Despite this reality there is a paucity of research that indicates how long individuals can work in extremely cold waters before their hand temperature drops below the critical thresholds for hand function. The purpose of this study was to investigate the timeline for hand function following exposure to 2 °C water. Participants immersed their hands in 2 °C water and then fine manual dexterity and tactile sensitivity were assessed every 30 s until the index finger temperature dropped below the critical temperature threshold. The results showed that the initial impairment in tactile sensitivity and fine manual dexterity occurred very quickly (90 s of exposure) and the critical temperature threshold was passed at approximately 120 s. These findings demonstrate that hand function will start to deteriorate in less than 2 min during exposure to extremely cold water and therefore the time window for safe and effective use of the hands in cold water is extremely short. Knowledge concerning the timeline for hand function following cold water exposure is relevant to industry because it can inform occupational time management practices, be used as a criterion for assessing occupational manual performance during training, and be used as a guide to modify behaviours and task requirements for cold water work.     

Tetrakis(alkylthio)-substituted lutetium bisphthalocyanines for sensing NO2 and O3

In this study, the nitrogen dioxide (NO₂) and ozone (O₃) sensing properties of a series bis[tetrakis(alkylthio) phthalocyaninato] lutetium(III) complexes [(C_nH_2n+1S)₄Pc]₂Lu(III) (n = 6, 10, 16) are investigated as a function of concentration in the temperature range between 25 °C and 150 °C. The concentration ranges were 1–10 ppm for NO₂, and 50 ppb–1 ppm for O₃. The response time and the sensor response to NO₂ are measured for approximately 1 min and 100% ppm⁻¹, respectively, for compound 1 at room temperature. At room temperature, all compounds are in the solid phase. The response time decreases to a few seconds with increasing operation temperature to 150 °C. At this temperature, all compounds are in the liquid crystal phase. The fastest response to oxidizing gases is observed at the liquid crystal phase of the Pcs. It has also been observed that the response time and the sensor response depend on the alkyl chain lengths of the Pcs. The doping effect of oxygen has been determined under high purity nitrogen N₂ flow, after exposure to dry air, at a different period of time and after annealing. It has been found that the conductivities of [(C_nH_2n+1S)₄Pc]₂Lu(III) thin films increased after exposure to dry air and the conduction mechanism also changed from ohmic behavior to space-charge-limited conduction.     

Impact of wet underwear on thermoregulatory responses and thermal comfort in the cold

The purpose of this study was to investigate the significance of wet underwear and to compare any influence of fibre-type material and textile construction of underwear on thermoregulatory responses and thermal comfort of humans during rest in the cold. Long-legged/long-sleeved underwear manufactured from 100% polypropylene in a 1 -by-1 rib knit structure was tested dry and wet as part of a two-layer clothing system. In addition cotton (1-by-l rib knit), wool (1-by-l rib knit), polypropylene (fishnet), and a double-layer material manufactured from 47% wool and 53% polypropylene (interlock knit) was tested wet in the clothing system. In the wet condition 175 g of water was distributed in the underwear prior to the experiment. The test was done on eight men (T_a = 10°C, RH = 85%, V_a < 01 m/s), and comprised a 60min resting period. Skin temperature, rectal temperature, and weight loss were recorded during the test. Total changes in body and clothing weight were measured separately. Furthermore, subjective ratings on thermal comfort and sensation were collected. The tests demonstrated the significant cooling effect of wet underwear on thermoregulatory responses and thermal comfort. Further, the tests showed that textile construction of underwear in a two-layer clothing ensemble has an effect on the evaporation rate from clothing during rest in the cold resulting in a significant difference in mean skin temperature. The thickness of the underwear has more of an influence on the thermoregulatory responses and thermal comfort, than the types of fibres tested.     

Physiological aspects of electrically heated garments

Abstract

Inactive man exposed to cold climates and dressed in conventional cold-weather clothing experiences difficulty in maintaining the temperature of the hands and feet. Comfort and performance, especially manual dexterity, are degraded as the temperature of the extremities falls with duration of exposure, and there is also the risk of cold injury. Electrical heating (EH) is a form of auxiliary heating which can offer a solution in some circumstances and is most useful when the wearer can conveniently connect to a power supply of a vehicle or some other type of military equipment. Physiological evaluations and user trials on various types of electrically heated (EH) items including coveralls, gloves, mitts, socks and insoles have been reviewed in this paper, using studies done by the Army Personnel Research Establishment (APRE) as the main source material. Cold-chamber trials showed the effectiveness of EH in maintaining hand temperatures and slowing the fall in foot temperatures even in the extremely cold climate of ?32^°C; however, impermeable outers worn over EH gloves, degraded the thermal protection available compared to leather outers. After user trials, whole-body heating in the form of coveralls was judged unnecessary provided that EH hand and foot protection and cold-weather clothing were available. A survey of a number of field trials has been undertaken with a view to extracting general advantages and disadvantages rather than those specific to a particular type of EH equipment. This survey indicated that the user perceived the advantages of EH clothing in terms of increased comfort and manual dexterity; however, users also pointed out disadvantages such as encumbrance, restriction to movement and durability problems. Clearly EH items need to be carefully tailored to the user's requirements and this may incur financial penalties.