Concentration substance-specific

For comparison a standard is kept by fixing the conditions of temperature and concentration. The specific rotation [a] D, which is practically constant and is characteristic of a substance is defined by the expression. 

In terms of waste definition, there are three basic approaches (as it pertains to petroleum, petroleum products, and nonpetroleum chemicals) to defining petroleum or a petroleum product as hazardous (1) a qualitative description of the waste by origin, type, and constituents (2) classification by characteristics based on testing procedures and (3) classification as a result of the concentration of specific chemical substances (Chapter 1). 

The evaluation of hazards posed to human health by toxic airborne chemicals is one of the common tasks employed in industrial hygiene. This process requires the collection of air samples to estimate air concentrations of specific substances inhaled by workers which can then be compared with standards and guides of acceptable exposure. Thus air sampling directly influences the formulation of important decisions. If air samples underestimate exposures, the consequence may be death or occupational disease. Conversely, overestimating exposures may result in the institution of unnecessary controls. Since either form of error is undesirable, it is fundamentally important that air sampling accurately define the extent of hazard. This requires that air samples be collected according to scientific, unbiased schemes for estimating exposures to toxic airborne chemicals. 

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