Explosive Limits Toxicity

Steam curtains are best used for diluting heavier-than-air releases of flammable vapors, not toxic materials. For flammable materials the level of dilution with air that has to be obtained is the lower explosive limit toxic materials could require dilution to <100 ppm range. Moreover, while steam curtains can provide the thermal effects that will help disperse flammable material, they hinder the absorption effects needed for toxic materials, especially materials that are water-soluble. 

Flammability and explosibility This section should indicate the NFPA rating for the substance, explosion limits, toxic substances that may be produced in a fire, and the type of fire extinguisher appropriate for fighting fires. 

Rash point, explosion limits, toxicity, maximum working place concentration, lower and upper flammability limits... 

Flammability Acrolein is very flammable its flash point is <0° C, but a toxic vapor cloud will develop before a flammable one. The flammable limits in air are 2.8% and 31.0% lower and upper explosive limits, respectively by volume. Acrolein is only partly soluble in water and will cause a floating fire, so alcohol type foam should be used in firefighting. The vapors are heavier than air and can travel along the ground and flash back from an ignition source. 

Butylenes are not toxic. The effect of long-term exposure is not known, hence, they should be handled with care. Reference 96 Hsts air and water pollution factors and biological effects. They are volatile and asphyxiants. Care should be taken to avoid spills because they are extremely flammable. Physical handling requires adequate ventilation to prevent high concentrations of butylenes in the air. Explosive limits in air are 1.6 to 9.7% of butylenes. Their flash points range from —80 to —73° C. Their autoignition is around 324 to 465°C (Table 2). Water and carbon dioxide extinguishers can be used in case of fire. 

Some vent streams, such as light hydrocarbons, can be discharged directly to the atmosphere even though they are flammable and explosive. This can be done because the high-velocity discharge entrains sufficient air to lower the hydrocarbon concentration below the lower explosive limit (API RP 521, 1997). Toxic vapors must be sent to a flare or scrubber to render them harmless. Multiphase streams, such as those discharged as a result of a runaway reaction, for example, must first be routed to separation or containment equipment before final discharge to a flare or scrubber. 

Tlie remainder of tliis cliapter provides information on relative physical properties of materials (flash points, upper and lower explosive limits, tlireshold limit values, etc.) and metliods to calculate tlie conditions tliat approach or are conducive to liazardous levels. Fire liazards in industrial plants are covered in Sections 7.2 and 7.3, and Sections 7.4 and 7.5 focus on accidental explosions. Sections 7.6 and 7.7 address toxic emissions and liazardous spills respectively. tliese latter types of accident frequently result in fires and explosions tliey can cause deatlis, serious injuries and financial losses. 

Property parameters. The physical property parameters include state of matter, phase equilibrium, thermal, mechanical, optical, and electromagnetic properties. The chemical property parameters include preparation, reactivity, reactants and products, kinetics, flash point, and explosion limit. The biological property parameters include toxicity, physiological and pharmaceutical effects, nutrition value, odor, and taste. 

The detection of a test gas using mass spectrometers is far and away the most sensitive leak detection method and the one most widely used in industry. The MS leak detectors developed for this purpose make possible quantitative measurement of leak rates in a range extending aaoss many powers of ten (see Section 5.2) whereby the lower limit = 10 mbar l/s, thus making it possible to demonstrate the inherent gas permeability of solids where helium is used as the test gas. It is actually possible in principle to detect all gases using mass spectrometry. Of all the available options, the use of helium as a tracer gas has proved to be especially practical. The detection of helium using the mass spectrometer is absolutely ( ) unequivocal. Helium is chemically inert, non-explosive, non-toxic, is present in normal air in a concentration of only 5 ppm and is quite economical. Two types of mass spectrometer are used in commercially available MSLD s ... 

F0-E°/T 46.96 c ° 13.31 (all in cal/deg mol) S°56.40 eu, H0, F0, c° S° are respectively standard heat of formation, stand free energy of form heat capacity std entropy. E° is heat of formation of a perfect gas. at abs zero (Ref 10) Acetylene chloride behaves very unpredictably It is spontaneously flammable in air and it explodes when heated in air or shocked. On pyrolysis it gives off the very toxic phosgene (Ref 8). An attempt at defining its explosion limits is made m Ref 2... 

Special attention must be given to the hazards involved in the use of solvents, and there is a general tendency to replace solvents that are hazardous, but have long been in use for historical reasons, with less dangerous solvents. For instance, benzene, a very useful solvent but known carcinogen, ought to be and actually often is replaced by the less hazardous toluene or xylene. Table A3 (see the appendices) provides some information concerning the toxicity of solvents on the table as well as their inflammability and the explosive limits of their vapor in air. 

Physical and Chemical Properties. While the principal properties of diazinon are well characterized, (ASTER 1995 Howard 1991 HSDB 1996 Merck 1989) there are data gaps for melting point, odor and taste thresholds, autoignition temperature, flash point, and explosive limits for the compound. Additional information on these properties would be helpful in assessing the compound s environmental fate. There are also data gaps for some spontaneously-produced degradation products some of which may be as toxic or more toxic than diazinon. 

The Phoenix diazomethane process can produce over 200 ty of chloroketone with an overall yield of 90% and in very high purity. This demonstrates a remarkable use of a highly explosive and toxic material (exposure limit of 0.2 ppm averaged over 8h) controlled by conhnuous generation and reaction. Thus, over 60ty" diazomethane are consumed per annum, but the maximum accumulated at any time is less than 80 g. 

The analysis of the potential consequences of an accident is a useful way of understanding the relative inherent safety of process alternatives. These consequences might consider, for example, the distance to a benchmark level of damage resulting from a fire, explosion, or toxic material release. Accident consequence analysis is of particular value in understanding the benefits of minimization, moderation, and limitation of effects. This discussion includes several examples of the use of potential accident consequence analysis as a way of measuring inherent safety, such as the BLEVE and toxic gas plume model results shown in Figures 4, 5, and 6. 

USEBLASTING - Comparable to 40% ammonia dynamite. High toxic fume production of this explosive limits its use to one where prevalent winds can cany these toxic fumes in a safe direction, away from the user. 

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