Hazardous, toxic, reactive chemicals

Checklists. A checklist is simply a detailed Hst of safety considerations. The purpose of this Hst is to provide a reminder to safety issues such as chemical reactivity, fire and explosion hazards, toxicity, and so forth. This type of checklist is used to determine hazards, and differs from a procedure checklist which is used to ensure that the correct procedure is followed. 

Information pertaining to the hazards of the chemicals used in the process. This should contain at least the following information toxicity, flammability, permissible exposure limits, physical data, reactivity data, corrosivity data, thermal and chemical stability data, and hazardous effects of inadvertent mixing of different materials that could occur. 

The testing of chemicals/wastes to establish the nature of their hazard capacity/threat in accordance with regulatory requirements falls into four categories (1) reactivity, (2) ignitability/flammability, (3) corrosivity, and (4) EP toxicity. Commercial chemical products, specific wastes, and wastes from specific processes may be listed as hazardous wastes because they are known to present toxic hazards in the manner of the tests above and/or are known to present serious toxic hazards to mammals/humans. In the discussion to follow, various chemical groups will be examined primarily in the context of reactivity, ignitability, and corrosivity. 

Highly Hazardous Chemical - Toxic, reactive, flammable, or explosive substances, as defined in Appendix A of 29 CFR 1910.119, "Process Safety Management of Highly Hazardous Chemicals."... 

Bretherick, Handbook of Reactive Chemical Hazards , CRC Press, Cleveland (1975), 843—45 9) Anon, Toxic and Hazardous Industrial Chemicals Safety Manual , The International Technical Information Institute, Tokyo (1975), 436—7 10) Anon, Fire Protection Guide on... 

Broaden the application to cover reactive hazards resulting from process-specific conditions and combinations of chemicals. Additionally, broaden coverage of hazards from self-reactive chemicals. In expanding PSM coverage, use objective criteria. Consider criteria such as the North American Industry Classification System (NAICS), a reactive hazard classification system (e.g., based on heat of reaction or toxic gas evolution), incident history, or catastrophic potential. 

There are OSHA standards designed to protect employees from acute chemical hazards resulting lfom reactive incidents-including fires, explosions, and toxic releases. The Hazard Communication Standard (29 CFR 1910.1200) requires chemical manufacturers to evaluate chemicals produced or handled in their workplace and to communicate the hazards associated with the products they produce via labels and MSDSs. The standard also requires all employers to provide information to employees about the hazardous chemicals to which they could be exposed. The PSM Standard (29 CFR 1910.119) requires employers to prevent or minimize the consequences of catastrophic releases of highly hazardous chemicals, including highly reactive chemicals. 

Reactivity. Chemicals that react violently with air or water are considered hazardous examples are sodium metal, potassium metal, and phosphorus. Reactive materials also include strong oxidizers such as perchloric acid, and chemicals capable of detonation when subjected to an initiating source, such as solid, dry < 10% H2O picric acid, benzoyl peroxide, or sodium borohydride. Solutions of certain cyanide or sulfides that could generate toxic gases are also classified as reactive. The potential for finding such chemicals in a refinery is... 

In snmmary, many of the specific chemicals in petroleum are hazardous because of their chemical reactivity, fire hazard, toxicity, and other properties. In fact, a simple definition of a hazardons chemical (or hazardous waste) is that it is a chemical substance (or chemical waste) that has been inadvertently released, discarded, abandoned, neglected, or designated as a waste material and has the potential to be detrimental to the environment. Alternatively, a hazardons chemical may be a chemical that may interact with other (chemical) snbstances to give a prodnct that is hazardous to the environment. Whatever the case, methods of analysis mnst be available to determine the nnrture of the released chemical (waste) and from the data predict the potential hazard to the environment. 

Independent of combustibility or reactivity, chemicals may exhibit hazardous properties that affect fire protection, in particular firefighting. Chemicals may be inherently toxic or radioactive. In either situation, potential exposure of smoke/gases to personnel from the burning of materials exhibiting these characteristics needs to be addressed. 

An obvious method for increasing the inherent safety of a production process is to substitute safer chemicals for more hazardous chemicals wherever possible. For example, flammable chemicals might be replaced by nonflammable chemicals explosive chemicals might be replaced by less reactive chemicals and highly toxic chemicals might be replaced by less toxic chemicals. 

Table 2 lists some of the physical, toxicity, flammability, and reactivity properties of common chemicals (10,13,42,45—51). Also given are some of the quantities specified for reporting spills and for compliance with legislated requirements. The OSHA regulations require that material safety data sheets (MSDS) be developed for all process materials, so that the hazard data can be communicated to employees (52). Characteristics of toxicity, flammability, chemical instability, reactivity and reaction energy, operating conditions, and corrosive properties of construction materials must all be considered in analyzing hazard potentials of chemicals and chemical operations. 

Fully cured polyurethanes present no health hazard they are chemically inert and insoluble in water and most organic solvents. Dust can be generated in fabrication, and inhalation of the dust should be avoided. Polyether-based polyurethanes are not degraded in the human body, and are therefore used in biomedical applications. Some of the chemicals used in the production of polyurethanes, such as the highly reactive isocyanates and tertiary amine catalysts, must be handled with caution. The other polyurethane ingredients, polyols and surfactants, are relatively inert materials having low toxicity. 

Some highly reactive chemicals and their dangerous properties are listed below. Those which give off highly corrosive irritant and/or toxic vapours or, if solids, are similarly hazardous in the form of dusts, are marked with an asterisk ( ) and should only be used in fume cupboards. More details concerning the properties of many of these are given in Section 4.2. Specific information on the hazardous properties of individual chemicals is collected in several comprehensive works.8 -11... 

Hazardousness Having a hazardous property. A chemical, procedure, or event that creates a substantial threat to human health and life. The United States Environment Protection Agency (US EPA) classifies hazardous wastes by four characteristics, including corrosivity (very alkaline (basic) (pH > 12) or acidic (pH 2) wastes), ignitability, toxicity, and reactivity (40 Code of Federal Regulations 261.20-261.24) (see Appendix E compare with toxicity characteristic and toxicity characteristic leaching procedure, TCLP). 

These factors are attributed to batch and semi-batch processes rather than continuous processes. However, the use of continuous processes on fine chemical manufacturing sites is limited. It is often preferable to use the semi-batch mode as opposed to batch processes. The Appendix lists hazards of pertinent chemical reactions for toxic and reactive hazards chemicals. Information concerning the safety of various chemicals (e.g., ammonia and others) can be readily obtained from the World Wide Web. Table 12-1 shows how to access a material safety data sheet at the Vermont Safety Information (VIRI) site on the Internet. 

Know all the hazards of the chemicals with which you work. For example, perchloric acid is a corrosive, an oxidizer, and a reactive. Benzene is an irritant that is also flammable, toxic, and carcinogenic. 

Classes of waste should be properly segregated for temporary accumulation and storage as well as for transportation and disposal. Accordingly, all wastes must be labeled properly before being removed. The label should contain sufficient information to ensure safe handling and disposal, including the initial of accumulation and chemical names of the principal components and any minor components that may be hazardous. The label also should indicate whether the waste is toxic, reactive, corrosive, metallic, flammable, an inhalation hazard, or lachrymatory. 

Housing two reactive chemicals that would generate toxic fumes when mixed within the same enclosure is an inherent safety blunder. According to the EPA report, three of the tanks had a total of 630,000 gallons of flammables. One of the tanks contained 340,000 gallons of sodium hydrosulfide (NaSH) as a 45% solution in water. One tank contained Briquest, a cleaning agent solution, and another was nearly filled with a relatively non-hazardous material. [11-12]... 

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