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SID - SATRA instrumented dummy

Using a heat and flame manikin to evaluate clothing performance under real fire simulations.

Understanding how materials and products perform when exposed to sources of heat and flame is fundamental to developing apparel and associated equipment intended to protect wearers from these hazards.

Traditional small-scale material testing, detailed in conventional European and international flammability standards, does not simulate what happens in real life scenarios such as that experienced by fire fighters or others. Here the clothing may be exposed to large-scale fires, and must provide adequate protection under those circumstances. In these situations the design and construction of the garment, and the way it is worn and sits on the body of the wearer can both have a crucial affect on heat and flame protective qualities, which can only be accurately simulated by subjecting the clothing to some form of whole garment test.

Human form manikin testing provides additional information which demonstrates more realistically the behaviour of apparel and provides manufacturers and users with a better understanding of the characteristics of high performance materials and clothing under these conditions. The results of fire tests conducted in this way are an important consideration for manufacturers and users of garments intended to provide protection during complete flame engulfment situations.

The use of manikins in European safety standards directly related to personal protective equipment (PPE) testing and CE marking is still in its infancy, therefore, currently most heat and flame manikin work is undertaken as research and development, on materials and apparel prior to production.

However, this is anticipated to change in the future as standards makers continue to revise and update PPE standards. For instance, EN 469 – 'Protective clothing for firefighters', details the use of a manikin as an optional garment test, as does EN ISO 11612.

The shoulders and elbows of the SATRA instrumented dummy ('SID') are articulated, principally to aid the donning of clothing. The 1,800mm-tall body is covered in thermal sensors, which are monitored using a sophisticated logging system capable of recording data at each sensor ten times per second. The manikin facility has been designed to assess all types of clothing including gloves, headwear and footwear. The flame source is a series of four vertical propane burner stations that can be placed at any position around the manikin to provide a uniform heat flux of up to 84kW/sq m. Each burner station incorporates three equal-spaced burners, each with an overall nozzle diameter of 50mm. Although the burners are applied for only a few seconds at a time (three to eight seconds typically) a considerable intensity of flames and heat can be produced.

During these tests it is possible that physical changes will occur to the garment which cannot be adequately predicted by the small scale swatch tests. In these incidents a wearer may sustain significant burns to a large area of his or her body, which might ultimately prove fatal. The burns however could occur in a number of ways. Firstly the textiles and composites may simply allow the heat flux to pass straight through the garment. Secondly, the garment might catch fire and become a secondary source of radiant heat only a few millimetres from the wearers skin. Thirdly, the garment might shrink thus bringing the heated materials into very close contact with the skin. It is, however, likely that all three mechanisms may play some role in injury.

Image © iStockphoto.com/ShaunLowe

Firefighters must be protected against the most arduous heat and flame conditions.

The purpose of manikin testing is to measure the effectiveness of protective clothing in reducing or eliminating skin burn injuries to the wearer. Human skin consists of a number of layers. The outermost layer, the epidermis, is normally approximately 50-80µm thick. The next layer is the dermis which is around 1.5 to 2mm thick. The layer below that is the sub-cutaneous layer. First degree burns are defined as reversible damage to the epidermis layer and a second degree burn is defined as damage to the dermis/epidermis which may be irreversible. A third degree burn destroys the epidermis and dermis and may damage sub-cutaneous tissue.

The software which controls SID has been written to calculate the resultant heat flux/time exposure from the temperature/time profiles for each sensor, and predict whether the level of burn for that sensor is none, first, second or third.

Using data from all sensor positions it is possible to build a picture of the total area of burns over the whole body. Protection is dependent not only on the basic protective qualities of the textile or composite but on factors such as: i) how the garment sits on the wearer, ii) the quality of the fit, iii) the presence of air gaps between the different layers or between the clothing and the skin of the wearer. The presence of undergarments can also have a significant effect on protection. The test can be used to compare different materials or different weights of the same material, different garments, or similar garments with different undergarments. Given that fit can be an important factor, the test can be used to compare the effects of a loosely fitting garment compared to a tightly fitting garment.

Manikin testing was introduced as a way of determining the effects of flame engulfment on a complete item of clothing and the wearer. In some areas of testing human subjects can be used for whole garment evaluation but this is obviously out of the question when testing the protection of whole garments against flame engulfment. The use of SID, coupled with other tests such as mechanical and physical testing and laundering processes, enables SATRA to provide manufacturers and end users access to a state of the art facility to assess their products under the most arduous of conditions.

Further information on SATRA's PPE certification and testing services is available at www.satra.com/ppe

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SATRA can carry out testing and certification of a variety of clothing intended to protect against heat and flame hazards. Please email ppe@satra.com for further information.