ASTM F1720 – 96 R04

Designation: F 1720 – 96 (Reapproved 2004) An American National Standard Standard Test Method for Measuring Thermal Insulation of Sleeping Bags Using a Heated Manikin1 This standard is issued under the fixed designation F 1720; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. INTRODUCTION Sleeping bags are used by people in outdoor environments to insulate them from the cold (that is, reduce their body heat loss to the environment). Sleeping bags often are used with ground pads and clothing inside tents that provide additional protection from the environment. The amount of insulation needed in a sleeping bag depends upon the air temperature and a number of other environmental factors (for example, wind speed, radiant temperature, moisture in the air), human factors (for example, a person’s metabolic heat production that is affected by gender, age, fitness level, body type, size, position, and movement), and physical factors (for example, amount of body coverage and the quality of the insulating materials). The insulation value, expressed in clo units, then can be used for sleeping bags and sleeping bag systems. 1. Scope 1.1 This test method covers determination of the insulation value of a sleeping bag. It measures the resistance to dry heat transfer from a constant skin temperature manikin to a rela- tively cold environment. This is a static test that generates reproducible results, but the manikin cannot simulate real life sleeping conditions relating to some human and environmental factors, examples of which are listed in the introduction. 1.2 The insulation values obtained apply only to the sleep- ing bag, as tested, and for the specified thermal and environ- mental conditions of each test, particularly with respect to air movement past the manikin. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use. 2. Referenced Documents 2.1 ASTM Standards: 2 F 1291 Test Method for Measuring the Thermal Insulation of Clothing Using a Heated Manikin 3. Terminology 3.1 Definitions: 3.1.1 clo, n—unit of thermal resistance (insulation) equal to 0.155°C·m2/W. 3.1.1.1 Discussion—A heavy men’s business suit provides 1 clo of insulation. 3.1.2 dry heat loss, n—heat transferred from the body surface to a cooler environment by means of conduction, convection, and radiation. 3.1.3 manikin, n—a life-size model of the human body with a surface temperature similar to that of a human being. 3.1.4 sleeping bag, n—a structure made of down, synthetic fiberfill, shell fabrics, or other materials, or a combination thereof, that is designed for people to use for thermal protec- tion when sleeping (for example, outdoors, tent, cabin). 3.1.5 thermal insulation, n—any material that increases the resistance to dry heat loss. 3.1.6 total insulation (IT), n—the resistance to dry heat loss from the manikin that includes the resistance provided by the sleeping bag and the air layer around the manikin. 3.1.6.1 Discussion—Total insulation values (IT) are mea- sured directly with a manikin. They can be used to compare different sleeping bags, as long as each test is conducted using the same experimental procedures and test conditions. 4. Summary of Test Method 4.1 A nude, heated manikin is placed inside a sleeping bag in a cold environmental chamber. 1 This test method is under the jurisdiction of ASTM Committee F08 on Sports Equipment and Facilities and is the direct responsibility of Subcommittee F08.22 on Camping Softgoods. Current edition approved May 1, 2004. Published May 2004. Originally approved in 1996. Last previous edition approved in 1996 as F 1720 - 96. 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. 1 Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. 4.2 The power needed to maintain a constant body tempera- ture is measured. 4.3 The total thermal insulation of the sleeping bag (includ- ing the resistance of the external air layer) is calculated based on the skin temperature and surface area of the manikin, the air temperature, and the power level. 5. Significance and Use 5.1 This test method can be used to quantify and compare the insulation provided by sleeping bags. It can be used for material and design evaluations. 5.2 The measurement of the insulation provided by clothing (see Test Method D 1291) and sleeping bags is complex and dependent on the apparatus and techniques used. It is not practical in a test method of this scope to establish details sufficient to cover all contingencies. Departures from the instructions in this test method may lead to significantly different test results. Technical knowledge concerning the theory of heat transfer, temperature and air motion measure- ment, and testing practices is needed to evaluate which departures from the instructions given in this test method are significant. Standardization of the method reduces, but does not eliminate, the need for such technical knowledge. Any depar- tures should be reported with the results. 6. Apparatus 6.1 Manikin3—Use a supine manikin that is formed in the shape and size of an adult male or female and is capable of being heated to either a constant temperature of 32 to 33°C or a constant mean skin temperature of 32 to 33°C, with a skin temperature distribution similar to that of a human being. 6.1.1 Size and Shape—Construct the manikin to simulate the body of a human being, that is, construct a head, chest/ back, abdomen/buttocks, arms, hands, legs, and feet. Total surface area shall be 1.8 6 0.3 m2, and height shall be 180 6 10 cm. Any departures from this description should be re- ported. 6.1.2 Surface Temperature—Construct the manikin so as to maintain a constant temperature distribution over the entire nude body surface with no local hot or cold spots. Ensure that the mean skin temperature of the manikin is 32 to 33°C. It is recommended that the average temperature of the hands and feet be lower (26 to 29°C). Do not allow local deviations from the mean skin temperature to exceed 63°C, except in the extremities. Evaluate temperature uniformity of the nude manikin at least once annually using an infrared thermal imaging system, a surface (contact) temperature probe, or equivalent method. This procedure also should be repeated after repairs or alterations are completed that could affect temperature uniformity, for example, replacing a heating ele- ment. 6.2 Power-Measuring Instruments—Measure the power to the manikin so as to give an accurate average over the period of a test. If time proportioning or phase proportioning is used for power control, then devices that are capable of averaging over the control cycle are required. Integrating devices (watt- hour metres) are preferred over instantaneous devices (watt metres). Overall accuracy of the power monitoring equipment must be within 62 % of the reading for the average power for the test period. Since there are a variety of devices and techniques used for power measurement, do not provide specific calibration procedures. Develop and document an appropriate power calibration procedure. 6.3 Equipment Measuring the Manikin’s Skin Temperature—The mean skin temperature may be measured with point sensors or distributed temperature sensors. 6.3.1 Point Sensors—Point sensors may be thermocouples, resistance temperature devices (RTDs), thermistors, or equiva- lent sensors. Ensure that they are no more than 3-mm thick and are well bonded, both mechanically and thermally, to the manikin’s surface. Bond lead wires to the surface or pass through the interior of the manikin, or both. Distribute the sensors so that each one represents the same surface area or area-weight each sensor temperature when calculating the mean skin temperature for the body. A minimum of 15 point sensors are required. It is recommended that a sensor be placed on the head, chest, back, abdomen, buttocks, and both the right and left upper arm, lower arm, hand, thigh, calf, and foot. 6.3.2 Distributed Sensors—If distributed sensors are used (for example, resistance wire), then the sensors must be distributed over the surface so that all areas are equally weighted. If several such sensors are used to measure the temperature of different parts of the body, then their respective temperatures should be area-weighted when calculating the mean skin temperature. Distributed sensors must be small in diameter (that is, less than 1 mm) and firmly bonded to the manikin surface at all points. 6.4 Controlled Environmental Chamber—Place the manikin in a chamber at least 3 by 2 by 2.6 m in dimension that can provide uniform conditions, both spatially and temporally. 6.4.1 Spatial Variations—Do not exceed the following: air temperature 61.0°C, relative humidity 65 %, and air velocity 650 % of the mean value. In addition, the mean radiant temperature shall not be more than 1.0°C different from the mean air temperature. Verify the spatial uniformity at least annually or after any significant modifications are made to the chamber. Verify spatial uniformity by recording values for the conditions stated above at 0.6 m (the midline elevation of the manikin on the cot) and 1.1 m above the floor at the location occupied by the manikin. Use sensing devices specified below when measuring the environmental conditions. 6.4.2 Temporal Variations—Do not exceed the following: air temperature 60.5°C, mean radiant temperature 60.5°C, relative humidity 65 %, and air velocity 620 % of the mean value for data averaged over 5 min (see 6.4.5). 6.4.3 Relative Humidity Measuring Equipment—Any hu- midity sensing device with an accuracy of 65 % relative humidity and a repeatability of 63 % is acceptable (for example, wet bulb/dry bulb, dew point hygrometer). Only one location needs to be monitored during a test to ensure that the temporal uniformity requirements are met. 3 Information on laboratories with heated manikins can be obtained from the Institute for Environmental Research, Kansas State University, Manhattan, KS 66506. F 1720 – 96 (2004) 2 6.4.4 Air Temperature Sensors—Shielded air temperature sensors shall be used. Any sensor with an overall accuracy of 60.15°C is acceptable (for example, RTD, thermocouple, thermistor). The sensor shall have a time constant not exceed- ing 1 min. The sensor(s) shall be located at the midline elevation of the manikin (0.6 m from the floor), at least 0.4 m from the manikin. A single sensor may be used, but multiple sensors are preferred. If a single sensor is used, it shall be located midway between the head and the feet. If multiple sensors are used, they shall be spaced equally from the head to the feet and their readings averaged. 6.4.5 Air Velocity Indicator—Use an omnidirectional an- emometer with 60.05 m/s accuracy. Average measurements for at least 1 min at each location. If it is demonstrated that velocity does not vary temporally by more than 60.05 m/s, then it is not necessary to monitor air velocity during a test. The value of the mean air velocity must be reported, however. If air velocity is monitored, then measurement location requirements are the same as for temperature. 7. Sampling and Test Specimens 7.1 It is desirable to test three identical sleeping bags so that sample variability will be reflected in the test results. Sample variance generally is larger for sleeping bags as compared with clothing. If only one sample is available, which is often the case with prototypes, however, replicate measurements can be made on one sleeping bag. 8. Preparation of Sleeping Bags 8.1 The sleeping bag should be the appropriate size for the manikin with respect to its width and length. A bag that fits tightly and causes compression in the head, feet, or hip areas may have a lower insulation value than one that does not cause compression. 8.2 Bags normally should not be laundered or dry cleaned prior to testing because the procedures may affect the results. 9. Test Procedure 9.1 Environmental Test Conditions—The standard condi- tions for all tests are given as follows. Other conditions are specified under Options 1 and 2. 9.1.1 Air Velocity—Use a fan to produce an air velocity of 0.3 6 0.05 m/s. Position the bag and manikin so that the direction of the air flow is from the head to the feet. 9.1.2 Relative Humidity—Maintain the relative humidity at a constant level 65 % between 30 and 70 % relative humidity for all tests conducted in a series. 9.2 Mean Skin Temperature of Manikin—Select an average temperature between 32 and 33°C and maintain it within 60.3°C for all tests conducted in a series. Do not allow the mean skin temperature to drift more than 60.1°C during a 30-min test. 9.3 Options—Select one of the following procedures. 9.3.1 Option 1—Select one air temperature for the chamber that is at least 20°C below the manikin’s mean skin tempera- ture and use that temperature for a series of tests. The power that it takes to keep the manikin heated to a constant, higher temperature will vary with the amount of insulation provided by the sleeping bag being tested. 9.3.2 Option 2—Select a watt level that corresponds to the sensible heat loss from a sleeping human being the size of the manikin. A person produces about 47 W/m2 of heat when sleeping. Assuming that 25 % of this heat is lost through insensible perspiration and respiration, 35 W/m2 is left to be lost through the skin. Consequently, a manikin with a surface area of 1.8 m2 would be operating at a 63-W level. Adjust the air temperature in the chamber until the proper watt level is achieved 65 W. NOTE 1—Option 2 is a more time-consuming procedure than Option 1 and depends upon the speed with which the chamber can change conditions. 9.4 Remove the sleeping bag from the stuff sack and shake it for approximately 1 min (that is, two people shall hold the bag, one at each end, and shake the bag, turning it periodically during the shaking). The bag needs to be shaken to reestablish the loft by incorporating more air after compression. Then lay it flat or hang it in an uncompressed state for at least 24 h prior to testing. 9.4.1 Position the manikin horizontally on a cot with a wooden frame that is 69 by 193 by 43 cm in dimensions and has a nylon cover (plain weave, 246 g/m2, 24 by 18 yarns/cm).4 9.4.2 Insert the manikin in the sleeping bag to be tested, securing all closures. Make sure the sides and ends of the bag are not compressed. For bags with a hood, secure the head opening by pulling the draw cord as snug as possible around the manikin’s head. The diameter of the opening should not be smaller than 5 cm. For bags without a hood, secure the head opening around the neck, exposing the head. 9.4.3 Bring the manikin to the selected skin temperature and allow the system to reach steady state (that is, the mean skin temperature of the manikin shall remain constant 60.1°C, and the power input shall remain constant 63 %). 9.4.4 After the sleeping bag reaches steady-state conditions, record the manikin’s skin temperatures and the air temperature at least every 5 min. The average of these measurements taken over a period of 30 min will be sufficient to determine the insulation value. Measure heater wattage (power) every 5 min or continuously over the test period. 9.5 Replication of Tests—The following options are permis- sible. 9.5.1 Most Preferred—Conduct three independent replica- tions of the test using three samples of a sleeping bag type. Sample variance, dressing variability, and instrumentation variability are reflected in the measurements. 9.5.2 Preferred—If only one sample of a sleeping bag is being tested, conduct three independent replications of the test by dressing the manikin in the bag three different times and taking data each time. Dressing variability and instrumentation variability are reflected in the measurements. 9.5.3 Adequate—If only one sample of a sleeping bag is being tested, three replications of the test may be conducted in 4 The sole source of supply of the apparatus known to the committee at this time is Byer Manufacturing Co., 74 Mill Street, Orono, ME 04473. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee 1, which you may attend. F 1720 – 96 (2004) 3 a row, a minimum of 1 h apart (for example, military specifications). Instrumentation variability is reflected in the measurements. 9.5.4 Least Preferred—Test one sample of a sleeping bag once. 10. Calculation 10.1 Calculate the total thermal insulation of the sleeping bag including the air layer resistance (IT), using the following equation: IT 5 K~TS 2 Ta!A P where: K = units constant = 6.45 3 clo 3 W/m2•°C, TS = mean skin temperature of manikin, °C, Ta = air temperature, °C, A = surface area of manikin, m2, and P = power supplied to the manikin, W. 11. Report 11.1 Report the following information: 11.1.1 State that the sleeping bags were tested as directed in this test method. Explain any departures from the specified apparatus or procedure, 11.1.2 Report the weight and surface area of the manikin, 11.1.3 Describe the sleeping bags that were tested, 11.1.4 Specify the environmental test conditions and proce- dure option used, and 11.1.5 Report the total insulation value (IT) in clo units and the number and type of replications conducted (see 9.5). Report clo values to one decimal point. 12. Precision and Bias 12.1 In comparing three observations of the thermal insula- tion value (IT) (measured on the same bag) the variation shall not exceed 63 % of the average of the three measurements when the measurements are taken in a row by the same well-trained operator using the same testing equipment. When measurements are made on different samples of the same type, the variance may be higher. 13. Keywords 13.1 clo; insulation; sleeping bags ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. 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