Reactive hazards pyrophoric

Reactive hazards, 44, 228 explosive, 235 mixtures, 231, 468 pyrophoric, 17, 214 thermal runaway, 252 unstable, 228 water-sensitive, 228... 

Pyrophoric and other spontaneously combustible substances will generally be identified as such on their product literature, material safety data sheets (MSDSs), or International Chemical Safety Cards (ICSCs). If transported, these substances should be identified as DOT/UN Hazard Class 4.2 materials for shipping purposes and labeled as spontaneously combustible. For pyrophoric substances, the NFPA 704 diamond for container or vessel labeling has a red (top) quadrant with a rating of 4, indicating the highest severity of flammability hazard (NFPA 704, 2001). Note that pyrophoric materials often exhibit one or more other reactivity hazards as well, such as water reactivity. 

Product stewardship, chemical reactivity hazard management, 29-30 Protective systems, documentation, 105 Pyrophorics, screening methods, 43-45... 

Since exposure of a spontaneously combustible material to air has obvious consequences, loss of containment or other means of air exposure is usually the most important issue regarding what can go wrong. It should be noted that p5n ophoric materials often exhibit one or more other reactivity hazards as well, such as water reactivity. Possible causes of uncontrolled reactions associated with pyrophoric and other spontaneously combustible materials include abnormal events such as the following ... 

Storage of uranium foil in closed containers in presence of air and water may produce a pyrophoric surface [1], Uranium must be machined in a fume hood because, apart from the radioactivity hazard, the swarf is easily ignited. The massive metal ignites at 600-700°C in air [2]. The finely divided reactive form of uranium produced by pyrolysis of the hydride is pyrophoric [3], while that produced as a slurry by reduction of uranium tetrachloride in dimethoxyethane by potassium-sodium alloy is not [4],... 

The potential thermal hazards associated with thermally unstable substances, mixtures, or reaction masses are identified and evaluated as in the flow charts Figures 2.3, 2.4, and 2.5. The potential hazards posed by reactivity—water reactivity, pyrophoricity, flammability, oxidizer contact, and so forth—are also included in Figure 2.3. The individual boxes in the flow charts are discussed below ... 

Several tests have been developed to identify the hazards of reactive substances [10]. Test methods for determining pyrophoric properties, water reactivity, and oxidizing properties (Box 17) are discussed in Section 2.3.4. 

Lists of pyrophoric materials that include less common chemicals, including metals, can be found in volume 2 of Brethericks Handbook of Reactive Chemical Hazards (Urben, 1999). Other spontaneously combustible substances are tabulated by their proper shipping names and UN/NA numbers in the U.S. Dept, of Transportation regulation 49 CFR 172.101. 

Chemicals that are water or air reactive pose a significant fire hazard because they may generate large amounts of heat. These materials may be pyrophoric, that is, they ignite spontaneously on exposure to air. They may also react violently with water and certain other chemicals. Water-reactive chemicals include anhydrides, carbides, hydrides, and alkali metals (e.g., lithium, sodium, potassium). 

CAUTION The flammability of magnesium is well known, and appropriate precautions must be taken when handling it (see note concerning fire extinguishers on p. 18). The more finely divided the magnesium, the greater the hazard, and the very reactive forms, especially the slurries described below, are PYROPHORIC in contact with air). 

Label all chemical containers with hazard details and hazard warnings as flammable, corrosive, organic peroxide, oxidizer, pyrophoric, unstable (reactive), water reactive, combustible liquid, compressed gas, explosive, acids, and/or incompatible. 

The disposal of residues from syntheses in which organometallic reagents were used (toxic, pyrophoric, water reactive, and flammable hazards)... 

Aluminum alkyls have been produced commercially since 1959 using technology originally licensed by Karl Ziegler. Aluminum alkyls are typically pyrophoric and explosively reactive with water (3, 9, 10). Considering such hazards, it is remarkable that thousands of tons of aluminum alkyls are produced each year and have been supplied for decades to the polyolefins industry worldwide with relatively few safety incidents. (However, see section 4.7.)... 

Polyethylene producers that use Ziegler-Natta, single site and selected chromium catalysts are required to handle metal alkyls on a large-scale (in some cases, tons per year). As previously noted, many metal alkyls are pyrophoric, i.e., they ignite spontaneously upon exposure to air. Most are also explosively reactive with water. Polyethylene manufacturers must routinely deal with these hazardous chemicals. Despite an abundance of resources and training aids from metal alkyl suppliers, accidents occur and severe injuries and even death have resulted. Clearly, safety and handling of metal alkyls must be a high priority. 

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