Smoke toxicity

Benzoxazines are heterocyclic compounds obtained from reaction of phenols, primary amines, and formaldehyde.98,99 As described previously, they are key reaction intermediates in the HMTA-novolac cure reaction.40,43 Crosslinking benzoxazine monomers at high temperatures gives rise to void-free networks with high Tgs, excellent heat resistance, good flame retardance, and low smoke toxicity.100 As in HMTA-cured novolac networks, further structural rearrangement may occur at higher temperatures. 

Knowing the impact of smoke toxic potency on escape from a fire is of sufficient importance that it has been the subject of research for over twenty years. As a result, we now have a realistic picture of proper contexts for the use of toxic potency data and a series of first-generation tools for measuring it. We also have a vision of the key technical issues to be resolved developing a proper small-scale fire simulator, relating rodent results to people, and validating the small-scale data. 

General Principles of Fire Hazard and the Role of Smoke Toxicity... 

Fire hazard is a combination of several properties, including ignitability, flammability, flame spread, amount of heat released, rate of heat release, smoke obscuration and smoke toxicity. 

During the 1970 s and early 1980 s a large number of test methods were developed to measure the toxic potency of the smoke produced from burning materials. The ones most widely used are in refs. 29-32. These tests differ in several respects the conditions under which the material is burnt, the characteristics of the air flow (i.e. static or dynamic), the type of method used to evaluate smoke toxicity (i.e. analytical or bioassay), the animal model used for bioassay tests, and the end point determined. As a consequence of all these differences the tests result in a tremendous variation of ranking for the smoke of various materials. A case in point was made in a study of the toxic potency of 14 materials by two methods [33]. It showed (Table I) that the material ranked most toxic by one of the protocols used was ranked least toxic by the other protocol Although neither of these protocols is in common use in the late 1980 s, it illustrates some of the shortcomings associated with small scale toxic potency of smoke tests. 

Figure 1. Categories of toxicity and lethal doses of various poisons and of the smoke from polymeric materials according to the NBS Cup Furnace Smoke Toxicity Protocol.

Thus, smoke toxicity is often very closely associated simply with the mass loss rate, since the toxicity in a fire scenario will be primarily a function of the mass ofsmoke per unit volume and per unit time being emitted into the ambient atmosphere. 

Fire safety in a particular scenario is improved by decreasing the corresponding level of fire risk or of fire hazard. Technical studies will, more commonly, address fire hazard assessment. Fire hazard is the result of a combination of several fire properties, including ignitability, flammability, flame spread, amount of heat released, rate of heat release, smoke obscuration and smoke toxicity. 

Fire hazard is associated with a variety of properties of a product in a particular scenario [1]. It is determined by a combination of factors, including product ignitability, flammability, amount of heat release on burning, rate at which this heat is released, flame spread, smoke production and smoke toxicity. 

Techniques are available to quantify the generation of smoke, toxic and corrosive fire products using the NBS Smoke Chamber (15), pyrolysis-gas chromatography/mass spectrometry (PY-GC-MS) (J 6), FMRC Flammability Apparatus (2,3,5,17,18), OSU Heat Release Rate Apparatus (13) and the NIST Cone Calorimeter (JJO. Techniques are also available to assess generation of 1) toxic compounds in terms of animal response (19), and 2) corrosive compounds in terms of metal corrosion (J 7). In the study, FMRC techniques and AMTL PY-GC-MS techniques were used. 

Generation of Smoke, Toxic and Corrosive Fire Products. Smoke, toxic and corrosive products are generated in fires as a result of vaporization, decomposition and combustion of materials in the presence or absence of air. 

In recent years there has been much controversy surrounding the impact of smoke toxicity following a fire. This has included discussions regarding means to measure toxic potency, by one of a variety of small-scale methods, and how to use these results to evaluate fire hazard. There has been, in particular, much speculation regarding the hazards due to certain plastics, typically poly(vinyl chloride) (PVC). 

Address the issue of PVC fire properties, including smoke toxicity and hydrogen chloride decay. 

In 1997, R.J. Reynolds Tobacco Co. introduced Eclipse, a nicotine delivery device purported to deliver lower levels of smoke toxicants than conventional cigarettes. Eclipse uses a carbon fuel element to vaporize nicotine in the rod the user then inhales the nicotine vapor. Venous plasma nicotine boost among ten smokers... 

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