Extract from the European Standard EN 13537

EXTRACT FROM THE EN 13537 EUROPEAN STANDARD

Based on this standard, testing of sleeping bags suitability is performed using human-like thermic figurine (dummy) that sends signals about temperature changes on particular part of the body. The dummy is placed into the tested sleeping bag and then the outer temperature is being changed. Based on measured values, the thermal purpose of particular sleeping bag is counted mathematically.

This European standard specifies definitions, common requirements and settlements for labeling and the information provided by the manufacturer of sleeping bags used for sports and leisure-time activities. This applied for sleeping bags designed for adults.

TERMS:

Standard thermal insulation
It is a quality of sleeping bag related to dry thermal loss of sleeping bag user (combination of thermal transmission by conduction, convection and radiation) and to difference of temperature between skin and surrounding air; measured on temperature model (dummy).

This defined thermal insulating standard represents sleeping bag insulating qualities that include filling performance, air pocket inside of sleeping bag, layer of air interface on outer surface of sleeping bag, sleeping bag underlay and clothes of user of sleeping bag.

Temperature model (dummy)
Temperature model in sleeping bag must occupy such inner volume in sleeping bag that is typical for adult lying on back. Dummy must be 1.5 to 2 m high and its surface must be 1.5 to 2 m2.

During the test, dummy is dressed in two-piece clothing with specific thermal insulation of material Rct = 0.049 m2K/W ± 10 % and in socks getting to knees with specific thermal insulation of material Rct = 0.054 m2K/W ± 10 %. Face of dummy is covered with face-mask.

Let’s assume that tested subject can perfectly take advantage of sleeping bag by adjusting its position and minimizing thermal loss, that he knows limiting factors of sleeping bag against that he can protect himself.

Artificial ground
This test is made with dummy lying on the ground made of solid support (12 mm thick) and underlay. Lower part of artificial ground must be in contact with surrounding air. Artificial ground is made of wooden board (55×185 cm, 12 mm thick) covered with mattress with thermal resistance 0.85 m2K/W ± 7 %. Wooden board is hold above floor on certain type of support that allows air circulation under the board.

Climatic chamber
This test is made in climatic chamber where deviation of temperature of surrounding air can not be more than ± 0.5 °C. Temperature is set at figure that guarantees that temperature gradient between dummy and air is higher than 15 °C. Difference between air temperature and radiation temperature of surrounding walls must be lower than 2 K. Air is taken for stationary. Air circulation speed inside of climatic chamber must be lower than 0.5 m/s (0.3 m/s by default). Relative humidity inside of climatic chamber can range between 40 % and 80 %.

Test and sample stage
Test is made on sleeping bag without previous treatment. Before the test, sleeping bag is adapted to surrounding test conditions that must last at least 12 hours.

Metabolically made heat
- elemental metabolically made heat for “lying at rest”,
- additional metabolically made heat – “shaking” (chill, thrill).

Effective thermal resistance of sleeping bag and effective evaporative resistance of sleeping bag is related to standard thermal insulation and to position that user adopts in the sleeping bag.

a) User of the sleeping bag that fights against cold is “curled into ball” and this way he minimizes heat loss.
b) User of sleeping bag that does not fight against cold however minimizes heat loss thanks to adequate body holding (e.g. lying on his side).

Heat loss because of respiration

Thermal debt
Thermal debt lead to lowering of inner body temperature. Physiological model applies to thermally balanced state. That is why we assume that thermal debt is zero.

TEMPERATURES:

Extreme temperature T_ext.

Lower temperature limit – in this case experienced user (woman) of sleeping bag (who adapts her clothes and position in sleeping bag to surrounding temperature and is able to take advantage of all possibilities of the sleeping bag) must expect strong feeling of cold. There is a risk of chill and health injure that can lead to death.
This temperature is calculated for standard woman (25 years old, 60 kg, 1.60 m tall, body surface 1.62 m2) when strongly exposed to cold that can last only for limited period, no more than 6 hours. Experienced user of sleeping bag is curled into ball in the sleeping bag and minimizes heat loss through sleeping bag (medium temperature of skin is 29 °C) and she shivers and elementary metabolic production rises. For inexperienced user this temperature is dangerous and it can lead to hypothermia and even to death.

Limit temperature T_lim.

Lower temperature limit – in this case experienced user of sleeping bag (who adapts his clothes and position in sleeping bag to surrounding temperature and is able to take advantage of all possibilities of the sleeping bag) in hunched position is in thermal balance and he does not feel cold. This temperature is calculated for standard man (25 years old, 70 kg, 1.73 m tall, body surface 1.83 m2, metabolic production 46 W/m2, thermal performance 82.8 W.) when he fights against cold curled into ball inside of the sleeping bag but in thermal balance and he does not shiver.

Comfort temperature T_comf

Lower limit of comfort range – in this case experienced user (woman) of sleeping bag (who adapts her clothes and position in sleeping bag to surrounding temperature and is able to take advantage of all possibilities of the sleeping bag) is in thermal serenity, it means she does not feel discomfort because of cold. User of sleeping bag who is in “relaxing position” (e.g. she is lying on her back) is in thermal balance and she does not feel cold. It relates to standard conditions of use. For inexperienced user this temperature correspond to feeling of discomfort because of cold. This temperature is calculated for standard woman (25 years old, 60 kg, 1.60 m tall, body surface 1.62 m2) who does not feel cold and does not shiver (in relaxed position).

Maximum temperature T_max

Upper limit of comfort range; temperature up to which user (partially uncovered) of sleeping bag (standard man) does not excessively sweat. This temperature is calculated for standard man (25 years old, 70 kg, 1.73 m, body surface 1.83 m2) in position with hands out of sleeping bag. Upper part of sleeping bag reach to armpit of dummy and its arms lies on top of the upper part of sleeping bag. Zips of sleeping bag are opened and hood is held down.

Warning concerning incorrect use of suggested temperatures

Thermal insulation of sleeping bag is affected by many factors – e.g. air humidity, wind speed, humidity of insulating filling of sleeping bag, quality of insulating underlay etc. Perception of thermal comfort depends on personal dispositions of individual and his hardiness etc.

Insulation of sleeping bag changes in accordance with using conditions, e.g. wind, radiating environment, position of user and his clothes inside of sleeping bag, insulation from ground, finite humidity inside of sleeping bag etc. Perception of cold is very individual. It depends on acclimatization, physic and psychic situation, food etc.

Limit temperatures of utility range (set according to European standard) compare only performance parameters of sleeping bags considering standardized testing conditions. Oscillation of conditions and individual reactions are not considered. That is why you should take this information as guidelines that must be individually adjusted in practice.

Given temperatures are theoretical limit temperatures based on thermal balance of whole body. Human body is very sensitive to local feeling of discomfort. Local thermal “bridge” need not influence whole insulation of sleeping bag but in a large measure it can influence feeling of cold of user of sleeping bag. It is necessary to point out that testing methods that are in accordance with this European standard do not guarantee that local algidity can not occur.

Temperatures valid for utility temperature range are related to inner conditions. When used outside, insulation of sleeping bag can be strongly influenced by outer conditions.

In this European standard sleeping bags are taken for dry. Humidity can radically worsen thermal performance parameters. In case of wet, material thermal loss can be up to 24 times higher than in case of dry material. Insulating material can absorb moisture from inside because of sweat and respiration and because of humidity outside of sleeping bag.