Reischl i Suradnici

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*Prof. Uwe Reischl, Ph.D., College of Health Sciences, Boise StateUniversity, Boise, Idaho, USA ([email protected]), Ravindra Go-onetilleke, Department of Industrial Engineering and Logistics Manage-ment, Hong Kong University of Science and Technology, Hong Kong,prof. Budimir Mioi, P.D., prof. Zenun Senderi, P.D., Faculty ofTextile Tecnology, Uniersity of Zagreb, Zagreb, Croatia.

UDK 687.172:535-1RECEIVED: 2010-11-08ACCEPTED: 2010-11-20

THERMAL CHARACTERISTICS OFINFRARED RADIATION PROTECTIVE VESTS

U. Reischl, R. Goonetilleke, B. Mijovi, Z. Skenderi*

SIGURNOST 53 (1) 51 - 56 (2011)PROFESSIONAL PAPER

INTRODUCTION

Solar infrared radiation can impose a signi-

cant eat load on worers wo are engage inoutdoor occupational activities. Agricultural

workers and construction workers are known to

be at high risk of heat stress. This situation is

especially critical when persons are required to

work in arid climates with high ambient air tem-

peratures and intense daytime sunshine. Such

conditions can lead to serious heat illnesses. Useof tents, hats, and other protective equipment

are frequently used in order to help reduce so-

lar heat exposure. However, such measures are

often impractical where employees are engaged

in complex manual tasks, interact with various

tools and equipment, and are required to chan-

ge body posture and locations frequently. Requ-

iring employees to wear protective garments in

such environments may be counter-productive

because garments can impose signicant eatstress by adding body insulation and thus redu-

cing air ow oer te sin. Tis, in turn, reducesconvection and subsequent sweat evaporation

capacity.

Physiologically, the human body is a meta-

bolic heat generating system which must ma-

intain a balance between heat loss and heat

gain within a narrow temperature range. Envi-

ronmental parameters such as air temperature,

air velocity, heat radiation, and humidity can

affect this delicate balance (Bishop et al., 1994.,

Holmer, 1995., Montain et al., 1994., Reischl,

Key words: heat stress, infrared radiation, heat attenuation vest, thermal manikin

SUMMARY: Solar eat radiation can impose signicant eat stress on employees performing ou-tdoor tass. A prototype infrared reecting vest was developed to offer protection to agriculturalworkers and constructions workers who are exposed to high levels of outdoor solar radiation.The prototype vest was tested using a laboratory based thermal manikin exposed to controlledheat radiation intensity levels. The tests showed that a vest including 3.2 cm spacers was ableto reduce eat gain by 30% witout imposing a signicant corresponding insulation eat gain.Te termal cross-over point for suc a vest was lowest in comparison to oters congurationstested. Commercial development of such a vest for use by agricultural workers and constructionworkers in desert environments is encouraged.


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SIGURNOST 53 (1) 51 - 56 (2011)U. REISChL, R. GOONETILLEkE, B. MIjOvI, Z. SkENDERI: Thermal characteristics ...

Figure 1. Prototype vest designed to reduce exposureto infrared radiation

Slika 1. Prototip prsluka za zatitu od

infracrvenog zraenja

Thermal manikin tests were conducted usingthe protocol described by Mijovic, Reischl, et.al.(2009., 2010.). All experiments were precededby a reference (control) run using a semi-nudemaniin conguration as illustrated in Figure 2.The photograph illustrates a semi-nude (control)maniin conguration. Enironmental air tem-perature conditions were maintained between22.50C and 23.50C, relative humidity between40% and 45%, and no external heat radiationexposure sources were present.

Both vests were evaluated for controlled heatradiation exposure conditions and for non-heatradiation conditions. Heat radiation was genera-ted using four 250 watt IR heat lamps directed atte cest of te maniin. Te reectie est was

tested with both the 1.6 cm spacers and the 3.2cm spacers. Te non-reectie est was testedusing te 3.2 cm spacers only. For comparisonpurposes, a lightweight fabric jacket (2.0 mmthickness) was evaluated under both non-radiati-on conditions as well as for radiation conditions.There were no spacers placed into this jacket.The manikin heat radiation exposure facility isillustrated in Figure 3. Te eat radiation produ-ced by the four IR lamps was directed onto thechest of the manikin.

Stransky, 1980.). Clothing material and gar-

ment design also impact the heat balance by

promoting or reducing heat exchange through

sweat evaporation, convection, conduction,

and heat radiation. In general, the protectiveperformance of fabrics is related to the chemi-

cal and physical structure of the fabric material

including thickness and weight. Woven textile

materials generally do not offer a good barrier

against infrared radiation. However, the perfor-

mance is generally better when the fabric thic-

kness is greater and when the fabric material is

heavier (Sun et al., 2000.).

Te deelopment of a ligt-weigt reecti-

ve vest was undertaken to offer an alternativestrategy for protecting agricultural workers and

constructions workers from excessively high

levels of solar radiation. Two prototype vests

were assembled and tested using a thermal ma-

nikin. Data were obtained that helped identify

optimal design features which will allow solar

reector ests to reducing infrared radiation im-posed heat stress.

METHODS AND PROCEDURES

Two vests were assembled for testing. The

ests consisted of a tin (1.0 mm) exible CBmaterial cut into a pattern that offered a simple

vest design including a front panel and a back

panel as illustrated in Figure 1. One est useda plastic reectie surface (Berry Plastics) wilete oter did not. Bot ests included exiblering-spacers that provided a gap between the

vest and the skin of the manikin. The spacerswere distributed uniformly over the front and

back panels. The spacers maintained a separa-

tion between the vest and the manikin skin of

1.6 cm and 3.2 cm. The vest consists of front

and back panels that are connected to each ot-

her over the shoulders. Inside both panels are

equally spaced exible plastic rings tat can beadjusted to provide either a 1.6 cm or a 3.2 cm

separation between the vest and the skin.


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RESULTS

Total manikin body heat gain was used as themeasure for heat stress. Total body heat gain

was also used to evaluate the insulation imposedon the manikin by the garments. The test resultsare summarized in Table 1.

Heat gain for both the control condition (se-mi-nude / unprotected) and the jacket at the 900watt exposure condition was 61.2 watts each.Te Non-reectie est exibited a eat gain of38.5 watts, while the aluminized vest includingthe 3.2 cm spacers exhibited a heat gain of 42.7watts. The aluminized vest, including the 1.6 cmspacers, exhibited a heat gain of 47.0 watts.

Table 1. Summary of manikin infrared heat gain valu-es for the control condition (semi-nude), fortwo prototype vests, and for the comparisonjacket

Tablica 1. Prikaz vrijednosti toplinskog prirasta zakontrolno stanje manekena, dva prototipaprsluka i jakne za usporedbu

ANALYSIS

The range of infrared heat radiation protec-tion offered by a garment can be dened by teTermal Inection Point (TIP) or temperaturecross-oer point as sown in Figure 4. Tis posi-tion identies te infrared eat radiation intensi-ty level above which a garment limits heat stress

Figure 2. Inatable termal maniin used for assessingte effectiveness of te prototype reective vests

Slika 2. Termalni maneken na napuhavanje koriten zaocjenjivanje uinovitosti reetirajueg prslua

Figure 3. Illustration of te inatable termal maniinexposed to infrared heat radiation while wearing the

prototype vest

Slika 3. Prikaz termalnog manekena na napuhavanje sprsluom izloenog infracrvenom zraenju

GarmentDesign

VentilationSpace

betweengarment and

skin

Measuredinsulationheat gain

without IR

exposure

Measuredheat gain forIR radiation

exposure

Manikinsemi-nude(Control)

N/A N/A 61.2 watts

Non-reectieVest (CB)

3.2 cm 1.5 watts 38.5 watts

AluminizedVest (AL)


AluminizedVest (AL)


Jacket 0 cm 17.1 watts61.2

watts


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heat protection while imposing the least insula-tion heat load. The difference between the vestwit an aluminized reectie surface and teest wit te non-reectie surface was not su-

bstantial. howeer, all congurations some eatgain as a result of vest insulation.

The relationship between the four vest desi-gns, te acet, and te semi-nude control con-guration is illustrated in Figure 5. It can be seentat all of te garment congurations proidedbenecial sielding. Te benecial effects incre-ased as the heat radiation exposure levels incre-ased.

Figure 5. Relationsip between IR exposure andmanikin heat gain observed for the semi-nude

control conguration, tree vest congurations, andcomparison jacet conguration

Slia 5. Odnos izmeu infracrvenog zraenja i prirasttopline manekena promatrane za kontrolno stanje,

tri prsluka i jaknu za usporedbu

Figure 5 also sows tat te non-reectie(CB) vest exhibited the lowest TIP cross-over po-

int and shown in Table 1 with an insulation heatgain of only 1.5 watts. The graph is based ondata obtained for te 0 IR exposure leel andthe 900 watt IR input level. The highest tempe-rature TIP cross-over point (and the highest base-line insulation value of 17.1 watts) was exhibitedby the jacket used for comparison purposes.

caused by infrared radiation. Below the TIP, agarment imposes unnecessary eat accumu-lation due to garment insulation. For protectieclothing in general, the TIP moves higher as theweight and thickness of a garment material in-creases and moves lower when garment weightand thickness decreases.

The goal of innovative garment design shouldbe to set the TIP as low as possible without de-creasing fabric material weight and thickness toa level where the protective characteristics of agarment material is jeopardized.

Figure 4. Illustration of te relationsip between body

heat gain due to heat radiation exposure and garmentimposed heat gain as a result of garment insulation

Slia 4. Priaz veze izmeu tjelesnog prirastatopline zbog izloenosti zraenju i toplinsi prirast

zbog izolacije odjeom

A simple method for moving the TIP lower,while maintaining garment integrity (weight andthickness), is to increase the ventilation charac-teristics of a garment. This can be achieved byproviding separation between the garment andthe skin. This space will allow convective andevaporative heat exchange to remove body me-tabolic heat freely. Such an approach can inclu-de the use of spacers that maintain the necessaryseparation between the protective garment andthe skin.

Table 1 illustrates the performance of the re-ector est wic includes 3.2 cm spacers. Itcan be seen that the vest offered the highest IR


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Montain, S.J., Sawka, M.N., Cadarette, B.S.Quigley, M.D. and Mckay, J.M.: PhysiologicalTolerance to Uncompensable Heat Stress: Effectsof Exercise Intensity, Protective Clothing, and Cli-

mate,J. Appl. Physiol., 77, 1994., 1, 216-222.Reischl, U. and Stransky, A.: Assessment of

Ventilation Characteristics of Standard and Pro-totype Firegter Protectie Cloting, TextileRes. J., 50, 1980., 3, 193-201.

Sun, G., Yoo, hS., Zang, XS., Pan, N.: Radi-ant Protective and Transport Properties of fabricsused by Wildland regters, Textile ResearchJournal, 70, 2000., 7, 567-573.

Mioi, B., Senderi, Z., Camara, j., Reiscl,U., Colby, C. and Mermerian, A.: Inatable Ma-nnequin for Testing Thermal Properties of Clot-hing, Proceedings of the 17th World Congress onErgonomics, Beijing, China, August 9-14, 2009.

Reischl, U. and Colby, C.: PNEUMOTECH: ANew Tool for Evaluating the Thermal Characteri-stics of Clothing Systems, Proceedings of the 4th

International Ergonomics Conference, BudimirMioic, Editor. Stubice Toplice, Zagreb, Croa-tia, pp. 29-36, June 30 July 3, 2010.

Reiscl, U., Mioi, B., Senderi, Z., ubi,I.: Heat Transfer Dynamics in Clothing Exposedto Infrared Radiation, Proceedings of the 3rd In-ternational Conference on Applied human Fac-tors and Ergonomics, Miami, Florida, USA, pp.589-598, July 17-20, 2010

CONCLUSIONS

Our results show that the use of a properlydesigned solar reector est can signicantly re-

duce infrared heat stress exposure. A vest with3.2 cm spacers was able to provide substantialprotection against infrared heat loading whileimposing only very minor insulation heat gain.Te application of an aluminized reectie sur-face did not measurably increase the infraredreection efciency of te est. Te TermalInection Point (TIP) for te ests wit 3.2 cmspacers was much lower than any of the othercongurations tested. Deelopment of a re-ector est for use by agricultural worers and

construction workers exposed to high intensitysunlight environments is recommended. We be-lieve that the application of this technology inarid regions of Africa and the Middle East mayprovide economic advantages by promotingoccupational health and safety and improvingproductiity in te eld.

REFERENCES

Bishop, P., Smith, G., Ray, P., Beaird, J. and

Smith, J.: Empirical Prediction of PhysiologicalResponse to Prolonged Work in EncapsulatingProtective Clothing, Ergonomics, 37, 1994., 9,1503-1540.

Holmer, I.: Protective Clothing and Heat Stre-ss, Ergonomics, 38, 1995.,1, 166-182.


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TERMIKA SVOJSTVA PRSLUKA ZA ZATITUOD INFRACRVENOG ZRAENJA

SAETAk: Sunevo toplinso zraenje moe prouzroiti toplinsi stres radnicima oji se baveposlovima na otvorenom. U ovome radu priazan je prototip prslua oji moe pruati zatitu odinfracrvenog zraenja poljoprivrednim radnicima te radnicima u graevini oji su izloeni viso-om stupnju sunevog zraenja na otvorenom. Prototip prslua je bio ispitan pomou laborato-rijsog termalnog maneena u uvjetima ontroliranog intenziteta toplinsog zraenja. Testovi supoazali da je prslu s udaljenosti izmeu oe i odjevnog predmeta od 3,2 cm smanjio toplinsiprirast za 30% bez znaajnog toplinsog porasta zbog izolacije. Taav prslu imao je najniu ter-malnu prijelaznu tou u usporedbi s ostalim testiranim postavama. komercijalni razvoj tavogprslua za poljoprivredne radnie i radnie u graevini je poticaj.Kljune rijei: toplinsi stres, infracrveno zraenje, prslu za smanjenje topline,termalni maneken

Struni radPrimljeno: 8.11.2010.

Privaeno: 20.11.2010.

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Reischl i Suradnici