Supporting Standards

The application of the above standards requires measurement or estimation of a number of parameters. The supporting and complementary standards de­scribed below provide information that is required for the application of stan­dards for assessing thermal environments. They can also be used independently in ergonomics and other investigations.

6.3.6.1 Metabolic Rate

All assessments of thermal environments require an estimate of the meta­bolic heat production of the occupants. ISO EN 8996 presents three types of methods. The first is by use of tables, where estimates are provided based on a description of the activity. These range from a general description (light,

TABLE 6.12 Wind Chill Index, WCI, Chilling Temperature, tch, and Effect on Exposed Flesh

WCi

(W m-1)

*ch

Cc)

Effect

1200

-14

Very cold

1400

-22

Bitterly cold

1600

-30

Exposed flesh freezes within 1 h

1800

-38

2000

-45

Exposed flesh freezes within 1 min

2200

-53

2400

-61

Exposed flesh freezes within 30 s

3600

-69

Heavy, etc.) to methods of summing components of tasks (e. g., basal metabolic rate + posture component + movement component). An example of activity levels is given in Table 6.13.

The second method is by use of the heart rate. The total heart rate is re­garded as a sum of several components and, in general, is linearly related to the metabolic heat production for heart rates above 120 beats per minute. Heat stress will, however, also increase the heat rate. The third method is to calculate the metabolic heat production from measures of oxygen consump­tion, and carbon dioxide production during activity and recovery.

6.3.6.2 Clothing

ISO EN 9920 provides a large database of thermal insulation values, which have been measured on a standing thermal manikin. One set of tables gives the insulation values for a large number of ensembles (Table 6.14). An­other set of tables gives insulation values for individual garments (Table 6,15), on the basis of which the insulation for a whole ensemble can be estimated.

The insulation of an ensemble, Ic, may be estimated as the sum of the in­dividual garment insulation values: Jci = ]l/ciu. The data on evaporative resis­tance are not so extensive. A few data are given in the standard, and a method to calculate the evaporative resistance based on the thermal insulation is also given. In the present standard no values are listed for the insulation of chairs, which may add 0.1-0.4 clo. Especially for the assessment of the level of heat stress, data on the evaporative resistance of clothing ensembles are important.

6.3.6.3 Instruments and Measurements

ISO 7726 provides a description of the parameters that should be mea­sured (air temperature, mean radiant temperature, plane radiant tempera­ture, air velocity, and humidity) together with methods of measurement

TABLE 6.13 Metabolic Rates

Activity

(W m J)

Met

Reclining

46

0.8

Seated, relaxed

58

1.0

Sedentary activity (office, dwelling, school, laboratory)

70

1.2

Standing light activity

(shopping, laboratory, light industry)

93

1.6

Standing, medium activity (shop assistant, domestic work, machine work)

116

2.0

Walking on the level

2 km k J

No

1.9

3 km h‘!

140

2.4

4 km h!

165

2.8

5 km h ‘

200

3.4

‘c,

»d

Work clothing

Clo

M2 K/W

Daily wear clottiing

Do

M* K/W

Underpants, boiler suit, socks, shoes

0,70

0.110

Panties, T-shirt, shorts, light socks, sandals

0.30

0.050

Underpants, shirt, boilersuit, socks, shoes

0.80

0.125

Underwear, shirt with short sleeves and legs, light trousers, light socks, shoes

0.50

0.080

Underpants, shirt, trousers, smock, socks, shoes

0.90

0.140

Panties, petticoat, dress, stockings, shoes

0.70

0.105

Underwear with short sleeves and legs, shirt, trousers, jacket, socks, shoes

1.00

0.155

Underwear, shirt, trousers, socks, shoes

0.70

0.110

Underwear with long sleeves and legs, thermo-jacket, socks, shoes

1.20

1.85

Panties, T — shirt, trousers, jacket, socks, shoes

1.00

0. i 55

Underwear with short sleeves and legs, shirt, trousers, jacket, heavy quilted outer — lacket and overalls, socks, shoes, cap, gloves

1.40

0.220

Panties, blouse, long shirt, jacket, stockings, shoes

1.10

0.170

Underwear with short sleeves and legs, shirt, rrousers, jacket, heavy quilted outer — jackct and overalls, socks, shoes

2.00

0.310

Underwear with long sleeves and legs, shirt, trousers, V — neck sweater, jacket, socks, shoes

1.30

0.200

Underwear with long sleeves and legs, thermo-jacket and trousers, heavy quilted outerjacket and overalls, socks, shoes, cap, gloves

2.55

0.395

Underwear with short sleeves and legs, shirt, trousers, vest, jacket, coat, socks, shoes

1.50

0.230

TABLE 6.15 Thermal Insulation for Individual Garments

Thermal insulation

Garment description

(clo)

Underwear

Pant its 0.0.3

Underpants with long legs 10

T-shirt

0.09

Shirts, blouses

Short sleeves

0.15

Norma!, long sleeves

0.25

Trousers

Shorts

0.06

Normal

0.25

Dresses, skirts

Light skirts (summer)

0.15

Heavy skirts (winter)

0.25

Winter dress, long sleeves

0.40

Sweaters

Thin

0.20

Thick

0.35

Jackets

0.90

Light, summer jacket

0.35

Jacket

0.40

High-insulative, fiber pelt

Boiler suit

0.90

Trousers

0.55

Jacket

0.40

Outdoor clothing

Coat

0.60

Parka

0.70

Sundries

Socks

0.02

Thick, long socks

0.10

Shoes 1 rhick-soled)

0.04

Boots

0.10

And specifications for the instruments (accuracy, response time, measuring range). Table 6.16 gives the accuracy required in the standard.

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