Protective Clothing

Managing Thermal Stress

F. Wang, Chuansi Gao

• Publisher: Woodhead Publishing
• Year: 2014
• Print ISBN:
  9781782420323
• eBook ISBN:
  9781782420408
• Topic: Technik & Maschinenbau
• Subtopic: Werkstoffwissenschaft

Protective clothing protects wearers from hostile environments, including extremes of heat and cold. Whilst some types of protective clothing may be designed primarily for non-thermal hazards (e.g. biological hazards), a key challenge in all protective clothing remains wearer comfort and the management of thermal stress (i.e. excessive heat or cold). This book reviews key types of protective clothing, technologies for heating and cooling and, finally, modeling aspects of thermal stress and strain. - Explores different types of protective clothing, their uses and their requirements, with an emphasis on full-scale or prototype clothing, including immersion suits, body armour and space suits - Considers novel and commercial technologies for regulating temperature in protective clothing, including phase change materials, shape memory alloys, electrically heated clothing and air and water perfusion-based cooling systems - Reviews the human thermoregulatory system and the methods of modelling of thermal stress in protective clothing through various conditions, including cold water survival and firefighting

Part I

Types of protective clothing and their requirements

Outline

1 Cold-protective clothing: types, design and standards

2 Cold-water immersion suits

3 Clothing for protection against heat and flames

4 Clothing for protection against hot-liquid splash and steam hazards

5 Chemical, biological, radiological and nuclear (CBRN) protective clothing

6 Ballistic-protective clothing and body armour

7 Spacesuits: development and design for thermal comfort

8 Medical protective clothing

1

Cold-protective clothing: types, design and standards

H. Mäkinen and K. Jussila, Finnish Institute of Occupational Health (FIOH), Finland

Abstract:

The effects and requirements of cold-protective clothing for human thermoregulation and thermal balance are considered. Material properties are discussed and the role and function of different clothing layers for regulating thermal comfort and avoiding thermal stress are examined. Protecting extremities is shown to pose particular problems, in particular when there is light physical activity. Some applications of cold protection are described and the legislation and standards required to ensure the safety of users are reviewed. Future trends for cold-protective clothing are discussed, including a variety of smart solutions and how several protective properties can be combined in clothing.

Key words

human thermoregulation; clothing comfort; cold-protective clothing; legislation; standards

1.1 Introduction: types of cold-protective clothing

Factors relating to physical work and the environment define how much insulation is needed in cold-protective clothing. Different types of cold environment (wet, dry, windy etc.) determine which properties of cold-protective clothing are needed in specific conditions.

Work can be considered as cold work at temperatures lower than + 10 °C according to the standard BS 7915 (1998). European standards (EN) for protective clothing define cold and cool temperature areas as follows:

EN 342 Protective clothing (2004). Ensembles and garments for protection against cold. Cold environment is defined in this standard as a temperature < − 5 °C.

EN 14058 Protective clothing (2004). Garments for protection against cool environments. Cool environment is defined in this standard as a temperature ≥ − 5 °C.

Cooling causes discomfort and impairs physical and mental performance in various ways (Raatikka et al., 2007). Frostbite, hypothermia and other cold-related injuries are related to body cooling. Frostbite is reported to occur amongst those working in cold indoor conditions (e.g. refrigeration units) or outside in cold weather such as agricultural and fishery workers, plant and machinery operators, assembly workers, technicians, reindeer herders and those in military training and operations (DeGroot et al., 2003; Ervasti et al., 1991; Mäkinen et al., 2009). Frostbite injuries are preventable by appropriate cold risk management which takes into account adverse effects of cold, individual adjustment of cold exposure, clothing and other organizational and technical measures (Ikäheimo and Hassi, 2011).

Selecting the appropriate clothing requires an understanding of the properties of different clothing layers and how they form a layered cold-protective clothing system. Cold-protective clothing creates a microclimate around the worker. This microclimate must prevent detrimental cooling and enable the worker to maintain a thermal balance. Even though cold-protective clothing and devices are needed to prevent the effects of cold on the body, it is also important to recognize the detrimental effects of clothing on physical performance, energy consumption, manual dexterity and sensory function, and limitations on movement, visual field and comfort (Dorman and Havenith, 2009; Dorman et al., 2006; Duggan, 1988; Havenith et al., 1995; Jussila et al., 2010; Rissanen, 1998).

Cold environments can be classified as natural, such as the locations of outdoor activities, or artificial, such as cold stores. Natural cold varies from mild and moist to dry and extremely cold, and thermal protective clothing varies accordingly. Although artificial cold conditions are stable throughout the year, workers often move from cold to warm temperatures. For occupational purposes, cold-protective clothing has to have other protective properties, such as high visibility, protection against mechanical and chemical hazards, or even protection against heat, sparks and flames.

In this chapter, the different types of cold-protective clothing, human responses to cold, requirements and design elements of cold-protective clothing, and also legislation and standards relating to cold protection and their testing are described. In addition, we look at examples of different types of cold protection and future trends in this area.

1.2 Human responses to cold

1.2.1 Human thermoregulation and thermal balance

Humans are homeothermic, which means that to maintain thermoneutral conditions their core temperature has to be within narrow limits around 37 °C. The human body produces metabolic heat by using its muscles and organs. This heat production can vary from 80 W at rest to over 1000 W for the most strenuous activity. Heat transfer from the body occurs through conduction (contact with cold surface or liquid), convection (air or water movement), radiation and evaporation of sweat or water/rain; heat loss by respiration plays a minor role. Air temperature, radiant temperature, humidity and air movement all affect human responses to the thermal environment. To maintain thermal balance, heat production and heat loss should be equal as presented by the heat-balance equation:

$\mathit{M}-\mathit{W}=\mathit{E}+\mathit{R}+\mathit{C}+\mathit{K}+{\mathit{E}}_{\mathrm{res}}+{\mathit{C}}_{\mathrm{res}}+\mathit{S}$ [1.1]

[1.1]

where M is the metabolic rate of the human body (W m^{− 2}), W is the mechanical work produced by the human body (W m^{− 2}), E is heat loss by evaporation of sweat (W m^{− 2}), R is heat loss by radiation (W m^{− 2}), C is heat loss by convection (W m^{− 2}), K is heat loss by conduction (W m^{− 2}), E_res is heat loss by respiratory evaporation (W m^{− 2}), C_res is heat loss by respiratory convection (W m^{− 2}) and S is heat stored in the human body (W m^{− 2}).

Cold-protective clothing prevents heat loss from the skin in low-temperature environments. Thermal balance depends on three components: ambient conditions, clothing insulation and metabolic heat production.

1.2.2 Effects of cooling

Human performance is negatively affected when core body temperatures are not between 36.5 °C and 37.5 °C. Lotens (1988) has produced a table of critical values of physiological parameters using comfort, discomfort, reduction in performance, tolerance and damage as criteria (Table 1.1).

Table 1.1

Approximate thermal strain criteria in the cold

Strain	Comfort	Discomfort	Performance degradation	Tolerance	Damage
Mean skin temperature (°C)	33	< 31	30	25	15
Finger temperature (°C)	27–34	< 20	< 15	5	− 2 − 15 (time dep.)
Toe temperature (°C)	24–34	< 17	< 13	5	− 2 − 15(time dep.)
Rectal temperature (°C)	37	38	< 36	< 35	28
Heat loss (J kg^− 1)	0	4	6	12	20

Source: Lotens, 1988.

Cooling affects human health directly and indirectly. If the body core temperature falls below 35 °C, the person becomes hypothermic. This can be sudden or develop gradually in too low temperatures when there are insufficient control measures such as protective clothing. Intense cooling of the skin, especially on the face or extremities, causes frostbite. Indirectly, the cold may make arthritis and asthma worse, increase cold injuries and decrease dexterity, mental skills and co-ordination. Working in cold weather may increase the risk of injury to muscles, for example, back strain, and may also lead to viral infections and chronic lung diseases.

Manual performance in the cold is affe...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Textiles
• Introduction
• Dedication
• Part I: Types of protective clothing and their requirements
• Part II: Technologies for warming or cooling in protective clothing
• Part III: Understanding and modelling thermal stress in protective clothing
• Index