Inherent safety elimination/substitution

The next step is to eliminate the hazard or substitute a hazardous chemical with one that is less hazardous. These concepts fall under the topic of Inherent Safety, which is discussed in detail in Chapter 8. 

In many cases, it may not be possible to entirely eliminate a hazard, but it may be feasible to substitute a high-risk hazard with one that has inherently less risk, thus improving inherent safety. For example, if the hazardous chemical RM-12 in the standard example can be replaced with another chemical that is less toxic and flammable, then the consequences of an overflow are reduced. Examples of substitution are given in the following sections. 

The primary philosophy is to follow the principles of inherent safety. This implies a systematic effort to apply the principles of hazard elimination, minimization/ intensification, hazard substitution, moderation/attenuation, and simplification. However, additional controls will still be required to control a hazardous situation, prevent escalation, and mitigate the risk to people, to the environment, asset, and reputation. Preferably, these safeguards will be passive- or active-engineered controls rather than administrative controls (i.e., dependent on direct human intervention). 

A primary objective of any safety program is to maintain or reduce the level of risk in the process. The design basis, especially inherently safer features that are built into the installation, must be documented. Management of change programs must preserve and keep the base record current and protect against elimination of inherently safer features. For identical substitution, the level of risk in the process is... 

Although substitution was motivated by the availability at that time of propylene and lower cost of the process, it was also a significant improvement in terms of safety, because acetylene is flammable and extremely reactive, carbon monoxide is also toxic and flammable, nickel carbonyl catalysts are toxic, environmentally hazardous (heavy metals), and carcinogenic, and anhydrous HCl (used in the reaction) is toxic and corrosive. However, the new process from propylene carmot be considered inherently safer. Hazards are primarily due to the flammability of reactants, corrosivity of the sulfuric acid catalyst for the esterification step (new solid acids have eliminated this hazard, as discussed in subsequent chapters), small amounts of acrolein as a transient intermediate in the oxidation step, and reactivity hazard for the monomer product. 

The plausible universe of alternatives to decaBDE for achieving fire safety in TV enclosures includes chemical substitutes, inherently flame resistant materials that eliminate the need for added flame retardant chemicals (for example, steel or aluminum), and TV re-design options that eliminate the need for flame retardants by separating the enclosure from the heat source. Alternative enclosure designs that eliminate the need for added chemical flame retardants and meet or exceed performance specifications (including flame retardancy) are considered inherently preferable alternatives, particularly if they are derived from benign chemicals (and safe processes) and are recyclable or compostable at end of life. 

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