**1. Introduction**

Historically, the arduous sectors of work described have been physically heavy such as work in the steel industry. In this context, this arduousness is related to significant thermal constraints caused by the production processes. In Tunisia, this sector employs more than 2498 workers [1]. Currently, the available tools for quantifying strain and thermal stresses are the result of a great research at the origin of European directive 89/654/EEC and of 14 standards developed by the International Standard Organization (ISO) [1–3]. This large number of thermal stress assessment tools reflect the complexity of prediction models and the difficulties in defining a simple model that can be used in various work situations [2]. This work was encouraged by the importance of the thermal constraints in the steel sector, the characteristics of the climate in Tunisia especially in the hot season and the employability of this sector. This research was conducted in the governorate of Monastir. It has a dry mediterranean climate with hot summers, extremely mild winters, much sunshine and low rainfall year-round. The city sits in the northeast of Tunisia, on its central coast. The average high temperature of 29°C (84°F) in June

skips past the 30°C (86°F) mark in the middle of the month and rises to 33°C (91°F) in July and August.

• a black globe thermometer (Black globe TP\_875.1/TP\_876.1) placed at the work station at a height of 1.5 m, keeping the employees apart. The

This evaluation was conducted by the program "Ergonomics of work in heat - Calculation of PMV indices - PPD, WBGT and P.H.S." developed by Prof. Malchaire [5] and based on the various physical parameters of the thermal environment (air temperature, black globe temperature, relative humidity, speed of air) as well as on:

• The equivalent metabolism M estimated based on the ISO 8996 standard "Ergonomics of the thermal environment - Determination of energy

• Iclo clothing insulation assessed in accordance with the ISO 9920 standard "Ergonomics of the thermal environment - Determination of thermal

insulation and resistance to evaporation of a clothing" [7] Thus, the program

◦ Predicted Mean Vote (PMV) at work and during recovery. This PMV index predicts the average vote value of a large group of people on the following seven-point thermal sensation scale: + 3 very hot; + 2 hot; + 1 slightly hot; 0 neither hot nor cold; �1 slightly cold; �2 cold; �3 very

◦ Predicted Percentage of Dissatisfied (PPD) in the workplace and during recovery. This PPD index is defined as the percentage of people who, placed in identical conditions, consider themselves cold/very cold or hot/very hot. These are the people who would have cast a vote outside the interval (�1, 1) on the sensation scale [1]. To obtain a thermal comfort situation, it is recommended that the PPD be less than 10%, which

◦ Thermal sensation in work situation and during recovery: This index is calculated from the PMV and PPD indices and In accordance with ISO 7730 "Ergonomics of the thermal environments - Analytical determination and interpretation of thermal comfort by calculating the PMV and PPD

◦ The natural humid temperature (Thn) in work situation and during

◦ The Wet Bulb Globe Temperature (WBGT) in the workplace and during recovery. The WBGT corresponds to a weighting between the radiation

<sup>¼</sup> <sup>0</sup>*:*7 thn <sup>þ</sup> <sup>0</sup>*:*2 tg <sup>þ</sup> <sup>0</sup>*:*1 ta with solar R (1)

corresponds to a PMV between �0.5 and + 0.5 [1].

indices and by local thermal comfort criteria" [8].

temperature and the natural wet bulb temperature.

WBGT ¼ 0*:*7 thn þ 0*:*3 tg without solar R

◦ The WBGT limits in work situation and during recovery

measurement time is about 20 min.

*Ergonomic Evaluation of Thermal Stress in a Tunisian Steel Industry*

**2.2 Thermal stress analysis**

*DOI: http://dx.doi.org/10.5772/intechopen.98697*

metabolism" [6].

cold [1]

recovery.

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identifies the parameters:

This work aims to assess thermal stress based on the various measurable thermal stress parameters (wet bulb temperature, air speed, radiation temperature, black globe temperature...).
