Marcelo M. Hirschler

Hydrogen Chloride Transport and Decay in a Large Apparatus I. Decomposition of Poly(Vinyl Chloride) Wire Insulation in a Plenum by Current Overload

Large-scale combustion product evaluation experiments were carried out in a realistic room-plenum arrangement. A 30 ft. (9.14 m) length of electrical power wire with flexible PVC jacket and insulation was decomposed, in a plenum, by the action of an electrical overload. The combustion gases measured were HCl, CO, CO 2 and unburned hydrocarbons. The maximum con centration of HCl in the plenum was 3000 ppm (which represents roughly one third of the total chlorine in the wire). However, this amount decreased rapidly so that only 200—300 ppm remained at the end of 30 min; none of the other combustion gases measured decayed significantly. Little or no HCl was found in the living space, except in one experiment with forced air recirculation, when a maximum concentration of 200 ppm was measured. Reasonable ac counting is presented for the very large proportion of HCl missing from the at mosphere.

Use of heat release rate to predict whether individual furnishings would cause self propagating fires

Abstract Limits have been developed, in specifications and regulations, for heat release rate of individual products, most frequently items of upholstered furniture or mattresses in different occupancies. These can be found, in the USA, in the Life Safety Code (NFPA 101), California Bureau of Home Furnishings and Thermal Insulation (CA TB 129 and CA TB 133), or Boston Fire Department regulations, and in recommendations by the European Combustion Behaviour of Upholstered Furniture (CBUF) project. Some of these criteria are based on fire hazard assessments and others solely on expert judgement. This work surveys test methods used for several individual furnishings, as well as usual acceptance criteria and the scientific bases for the threshold values used. In particular, this work investigates the concept of self-propagating fire, often ignored when setting arbitrary limits. Moreover, this work also considers the relationship between the thermal insult applied to the product and its potential impact on fire hazard, especially in view of some potential techniques utilized for obtaining product approval. This work also compares some results obtained using a small scale heat release technique, the cone calorimeter, and its efficacy in predicting actual full scale test results, mainly in terms of fire hazard, rather than the satisfaction of individual test requirements. Finally, the work also investigates, briefly, the relative criteria to assess the probability of an interior finish material to cause a self-propagating fire. For such materials, requirements are in place frequently, but heat release rate is rarely used as the basis of requirements. In conclusion, this work demonstrates that heat release rate test criteria can be used to assess fire hazard from many, if not most, individual furnishings.

How to Measure Smoke Obscuration in a Manner Relevant to Fire Hazard Assessment: Use of Heat Release Calorimetry Test Equipment

In the first section of this paper smoke obscuration measurement tests are being classified according to the type of equipment used (static or dynamic), the scale and the other properties measured. The conclusion of this section is that the most adequate means to measure smoke obscuration, so as to have results useful for fire hazard assessment, is by determining a combina tion of heat release and smoke release, e.g., with the cone or OSU calorimeter.

Rate of heat release testing for vinyl wire and cable materials with reduced flammability and smoke—full-scale cable tray tests and small-scale tests

Abstract Various cables were prepared with vinyl compounds, and their fire performance tested in full-scale modified cable tray tests and in a small-scale RHR calorimeter test (cone calorimeter). The cables passed all full-scale tests, except for two THHN cables (including a nylon film), made with a traditional jacket compound and not flame retarded. Information obtained from the cable tray tests included heat release, smoke release, mass loss and gas release (CO, CO2 and HCl). The smoke obscuration from the full-scale burns was heavily dependent on the extent of burning of the cables. Those cables that did not burn extensively released very little smoke. Similarly those same cables released very low amounts of combustion gases, notably HCl. Results of cone calorimeter tests on cables were well correlated with full-scale test results, both in terms of heat and smoke release. This was particularly true for the cone used at a 20 kW/m2 flux. In terms of smoke release, the total smoke released in full scale correlates well with smoke factor in small scale. Total smoke released in small scale is a much less reliable measure of full-scale smoke release than smoke factor. All vinyl compounds used to make the cables were also tested in the cone and in the OSU calorimeter. Correlations were also made of properties between both calorimeters, and were found to be excellent. Some fire properties of the jacket compound alone, in the cone calorimeter, at 20 kW/m2, can be used to give an indication of likely cable performance in a full-scale test. The best properties to be used are peak rate of heat release and smoke factor. The OSU calorimeter is less reliable as a small-scale predictor, based on jacket results only. The experimental vinyl wire and cable compounds developed show excellent fire performance in small-scale tests and show excellent fire performance when made into experimental cables.

A Comparative Study of the Fire Performance of Halogenated and Non‐Halogenated Materials for Cable Applications. Part II Tests on Cable

A total of 21 electrical cables were made, all with essentially identical construction but differing in the chemical composition of sheath and/or insulation, which were all commercially available materials, both halogenated and non-halogenated. All cables were tested in two large-scale cable tray tests, ASTM D5424 (CSA FT-4 protocol), with a total length of 2.44 m and IEC 332-3, with a total length of 3.5 m. The cables were also tested in a number of small- and medium-scale tests for flame spread (IEC 695-2-2, IEC 332-1, UL 1581 Part VW1, BS 476 Part 12E, DIN 4102 Part 16), temperature increase (DIN 4102 Part 16) and smoke obscuration (IEC 1034-2, BS 476 Part 12E). Finally, all cables were tested in the cone calorimeter (ISO 5660), horizontally, at incident fluxes of 20, 40 and 70 kW m−2. All the cables passed the mild flammability tests, but distinctions could be made based on the afterflame time observed, where halogenated cables outperformed non-halogenated cables by a significant margin. It was also possible to distinguish between the halogenated and non-halogenated cables on the basis of the cable length charred in some tests. In terms of smoke obscuration, it was found that the rankings offered by the various tests were very different. While non-halogenated cables had improved smoke performance over traditional vinyl types, fluorinated cables performed very well. This confirms the importance of material selection by performance rather than by chemical composition. Almost all cables performed sufficiently well that they generated relatively limited amounts of smoke under realistic end-use fire test conditions. The peak heat release rate in the large-scale cable tray test (ASTM D5424) served as an excellent criterion for discriminating between the fire performance of the various cables (the traditional criterion being char length). The average rate of heat released also served to distinguish between different levels of cable fire performance. Moreover, cables passing the test tended to release less heat and smoke than those that failed. The trends observed in the cone calorimeter heat release test were similar to those in the large-scale test and show good correlation between cable tray char length and cone calorimeter heat release. It was observed that the halogenated cables tested performed better than the non-halogenated cables in terms of heat release rate by factors ranging from two to greater than five. The results indicate that cables with excellent fire performance can be constructed by using a variety of materials. It is thus important to specify fire performance and leave material choice to manufacturers.

Soot From Fires: II. Mechanisms of Soot Formation

The mechanisms described for soot formation have been reviewed. It is clear that no one simple mechanism can yet totally describe the complex processes in volved. It has been well established that ions have an important role in the nucleation stage, but controversy still surrounds the extent of their importance as precursors of soot. In the case of polymeric fuels, the gaseous fuels produced by thermal breakdown of the polymer are small organic molecules, which will then, generally, produce soot by mechanisms similar to those for fuels originally gaseous.

A Comparative Study of the Fire Performance of Halogenated and Non-Halogenated Materials for Cable Applications. Part I Tests on Materials and Insulated Wires

This paper, the first of a series of three, describes the results of an extensive study of the mechanical physical, electrical and fire properties of polymeric materials, both halogenated and non-halogenated, intended for cable applications. The objective of this study was to provide, by means of generally recognized standard tests, data, which should make possible a dispassionate fire hazard analysis of the relative merits of materials. Excellent materials were found with different chemical compositions. The results indicate the following: (1) Materials can be suitable for wire and cable applications irrespective of their chemical composition. (2) Halogen-containing materials, as a group, tend to outperform non-halogen materials in terms of the major fire properties: •Heat release •Ignitability •Flammability (3)Most commercial materials tend to have adequate mechanical and physical properties, but halogenated materials are, as a rule, slightly more satisfactory. (4)Compared to fire retarded non-halogenated materials, halogen-containing materials tend to have better performance in terms of some of the more important electrical properties, particularly dielectric breakdown voltage. (5)The resistance to ageing of non-halogenated materials is somewhat suspect, particularly with respect to attack by oils. (6)The smoke obscuration per unit mass of non-halogenated (polyolefin-based) materials is superior to that of vinyl-based materials, but differences are significantly reduced when considering the expected smoke obscuration in actual full-scale fires, due to the overall lower tendency of halogenated materials to burn; the smoke obscuration resulting from fluorinated materials is also low. (7)Smoke corrosivity is the single property where non-halogenated materials clearly outperform halogenated materials.

Smoke Toxicity Measurements Made so that the Results Can Be Used for Improved Fire Safety

The toxic potency of the smoke generated from most materials in a fire is very similar. The toxicity of fire atmospheres in those fires causing most fatalities (large flaming fires with ventilation control) is principally asso ciated with the presence of carbon monoxide (CO). In those particular fires (which are of greatest concern for fire hazard assessment) there is, moreover a very poor correlation between carbon monoxide concentrations and fuel chem istry. This is due to CO yields being dominated by the conditions in the fire compartment and bearing little relation to the chemical structure of the materials being burned. Toxic potencies measured in bench scale tests are often dominated by combustion products other than carbon monoxide, since these tests generally do not give adequate carbon monoxide yields. Thus, ana lytical results from such tests have no value, either scientific or for fire hazard assessment.

Soot From Fires: I. Properties and Methods of Investigation

A literature survey has been carried out on the formation of soot from flames, in particular as relevant to fires. The properties of soot are very similar irrespec tive of the origin, but the effects of various parameters and additives are significantly different for diffusion flames and premixed flames. If the fuel is polymeric, the chemical structure of the polymer and its thermal breakdown mechanism will govern the amount of soot produced.

Analysis of thermal performance of two fabrics intended for use as protective clothing

Tests were conducted on two fabrics intended for use in protective clothing: an aramid (used extensively in firefighter gear) and a modified viscose cellulosic fabric. Both were exposed to very high heat (temperatures above 400°C) and their performance as thermal insulators was assessed by the temperature transmitted through the fabric, both in their dry state and after being exposed to a water spray. Both fabrics performed satisfactorily, but the modified viscose fabric improved its thermal insulation properties when damp, while the aramid fabric remained unaffected (or perhaps negatively affected) by the water spray. Overall, the modified viscose fabric seemed a better thermal insulator than the aramid.