John F. Krasny

Protecting fire fighters exposed in room fires: Comparison of results of bench scale test for thermal protection and conditions during room flashover

Heat flux conditions measured in seven room fires are discussed. The conditions varied from just below flashover in a sparsely furnished bedroom to flashover and severe postflashover fire in a typically furnished recreation room. These heat flux conditions are compared with the protection level provided by fire fighter turnout coats conforming to NFPA 1971,Protective Clothing for Structural Fire Fighting. This standard requires that the turnout coat or pants assembly must protect the wearer against second degree burns when a heat flux of 84 kW/m2 (2 cal/cm2.s) is applied to its outside surface for a minimum of 17.5 seconds [“thermal protective performance (TPP) of 35”]. The results imply that fire fighters have only ten seconds or less to escape under most flashover conditions. However, the turnout coats provide good protection in many other fire situations. Practical definitions for flashover are given, and possible means for making the TPP test more relevant for research and development work are discussed.

Laboratory Modeling of Garment Fires1

In an attempt to model real-life burn accidents, garment assemblies were burned on adult-size mannequins and the temperature distribution over the mannequin surface determined. Anaesthetized, shaved rats were exposed in openings of the mannequinns in the spatial arrangements encountered in real-life garment fires. The correlation between the depth of burn into the skin and the temperature observed on the mannequin surface near the exposed skin seemed fair. In other experiments, the interaction of burning fabrics and depth of burn was studied by means of simulated garments fitted to anaesthetized, shaved rats. Garment geometry was found to affect the burn injury potential as much as fabric parameters. It is discussed in terms of initial fabric to skin, fabric to mannequin, and outerwear-underwear distance (these distances often change during the fire due to heat shrinkage of thermoplastic fibers, turbulence, etc); formation of chimney spaces between fabric layers and the mannequin surface; and firestops such as belts. Other experiments covered the effect of combinations of various fabrics, such as dress-slip assemblies. Garments made from flame-retardant (FR)-treated cotton fabric and 100% thermoplastic fibers did not ignite in our experiments when used as single layers. When combined with polyester/cotton blends in outerwear-underwear assemblies, these fabrics caused smaller areas of the mannequins to be raised to elevated temperatures than the blend fabrics alone. This effect was particularly marked for the FR treated cotton. In our experiments, polyester/cotton blends seemed to have more potential for causing injury than comparable, 100% cotton fabrics. 100% thermoplastic fiber fabrics appeared to have a low injury potential. The effect of fabric weight on the area of the mannequin raised to elevated temperatures was not clear cut, though it was obvious that heavier fabric caused more severe injury to exposed skin, and were more difficult to extinguish by beating out the flames, than light fabrics.

8 – Fire Hazard Analysis

This chapter illustrates the upholstered furniture fire problem with respect to fire hazard analysis. The fundamental hazard to life that a person can encounter during the course of a furniture fire is the exposure to a lethal or incapacitating atmosphere. This consists of four elements: high concentrations of toxic gases, high levels of thermal radiation, high temperature air, and smoke obscuration that can interfere with the ability to escape. The relative importance of these hazard elements varies according to the type of fire: well ventilated, propagating fire; under-ventilated propagating fire; non-propagating fire; and smoldering fire. The chapter also discusses therole of other factors such as the distance from the fire, smoke and toxic gases, and toxic potency differences among commercial materials.

Crease Recovery of Fabrics Part I: Some Tensile Properties of Wool, Vicara, and Rayon Fibers and Their Relationship to Fabric Crease Recovery

A study has been made of some single fiber properties of wool, rayon, and Vicara zein fibers at various relative humidities, and the crease recoveries of fabrics made from the same fibers have been measured under identical conditions. In general, the wool and Vicara are similar in many load-extension properties. A fair correlation was found between fabric crease recovery on the one hand, and fiber tensile and work recovery on the other hand at low and normal humidities. At high humidity, and particularly with wet fabrics, however, this relationship no longer holds. A general correlation also seems to exist between fabric crease recovery and work returned by stretched fibers during retraction from extension to 4%.

Protecting fire fighters exposed in room fires, part 2: Performance of turnout coat materials under actual fire conditions

Seven experimental fires varying in fire load were conducted in a simulated townhouse. Specimens of various current fire fighters turnout coat materials were exposed in the room of fire origin. The time at which conditions would become untenable for the fire fighter due to pain, as well as the time to second degree burn, were calculated. These times ranked the coat specimens in roughly the same order as the “Thermal Protection Performance” measured according to NFPA 1971–1986, especially if the heat in the room developed rapidly.

Burning Behavior of Upholstered Furniture Mockups

Furniture mockups consisting of various arrangements of full-size cushions were tested in the NBS furniture calorimeter. Measurements included heat release, combustion product concentrations, and flame spread characteristics. Major variations in burning were observed: neoprene mockups only smoldered, flame retardant treated polyurethane mockups burned more slowly than un treated mockups but eventually reached similar maximum heat release rates. Fabrics were ranked, in terms of maximum heat release rate and several other measured characteristics, from low to high: heavy cotton fabric; light cotton and heavy olefin, and light olefin. Flame spread rate measured on the mockups cor related with the time to reach a 100 kW heat release rate. Heat release rate and combustion product concentration generally increased with increasing number of cushions per mockup. Thinner cushions burned more rapidly than thicker ones.

Flammability Evaluation Methods for Textiles

This chapter will discuss flammability evaluation of fabrics as well as of end-use items containing fabrics, such as apparel, curtains and draperies, tents, mattresses, upholstered furniture, etc.

Improved Single-Unit Schiefer Abrasion Testing Machine

An improved single-unit Schiefer abrasion testing machine was developed. It can be adapted for testing a great variety of materials under a wide range of test conditions. Different types of specimen holders and abradants can be used with the machine. Both the pressure and the tension on the specimen can be fixed at selected values and maintained constant throughout the test period. A variety of materials, including woven, knitted, and coated fabrics, plastics, paper, leather, and other materials, were abraded with the machine. The abrasive wear of each material was found to be extremely uniform over the abraded area. The effect of the amount of plasticizer on the resistance to abrasion of plastics was readily measured. The rate of abra sion was directly proportional to the amount of plasticizer present. The abrasive wear in tests of woven fabrics appeared very similar to that which occurred in service. A quantitative method based upon the change in electrical capacitance of the specimen with abrasion was de scribed for evaluating the amount of abrasion. A quantity which is a measure of abrasive destruction or ruin was defined. This quantity was used to obtain an iso-ruin map of a large area of a trouser leg. This iso-ruin map showed very clearly a number of areas at which ex cessive wear in service had occurred. The change of the abradant during abrasion tests is discussed. Carborundum paper, a generally used abradant, decreased very greatly in abrasive power. The spring steel blade abradant remained essentially constant, although in testing one resin-finished fabric the surfaces of this abradant became coated with the resinous substance, which greatly increased its abrasive power.

Note on the Disintegration of Wool in Abrasion Tests

The coating which formed on the abradant when a specimen of wool fabric was abraded and caused the rate of abrasion to increase approximately ten times in three successive tests was examined critically. Microchemical analyses showed that it had the same composition as the unabraded fabric. Infrared absorption curves of the coating and of the powder of the unabraded fabric, ground in a vibratory ball mill, showed the same absorption characteristics. Electron micrographs of the coating showed that it contained extremely small particles, many of which were approximately spherical in shape and about 100 to 200 A. in size. Similar particles were observed in the abraded debris when the specimen was kept wet with water during the abrasion test, and also in the powder into which the unabraded fabric was ground in the vibratory ball mill. It was concluded that the coating which formed on the abradant consisted of extremely small particles of wool which appear to correspond in shape and size to the elemental structural units (keratin molecules) proposed in recent concepts of the structure of wool.

Upholstered Furniture Transition from Smoldering to Flaming

This paper reviews the available literature on experimental measurements of smoldering to flaming transition in upholstered furniture. It is found that of 102 items, 64% made the transition to flaming. For the items which transitioned to flaming, the time for the transition to occur ranged from 22 to 306 min. Some of the factors affecting the likely time to transition are known qualitatively, but a quantitative method of prediction is not available which would allow one to predict such transition occurrence (and time) on the basis of construction details and fire environment.