Document wg7orD3g2xV8vJj24Ow0Q4eyV

174 FRANK A. PATTY industrial hygienist, either extremely small quantities of materials must be deter' mined or else provision must be made for sampling a large volume of air. The mof toxic gases and vapors are of hygienic importance when found to be present ' amounts even less than 1 ml. per cubic meter of air (1 p.p.m,), and many dusts anB fumes are of interest in amounts of less than 1 mg. per cubic meter of air. Methods, of analysis based upon microchemical technique, especially colorimetry, are frc quently preferred because they can utilize a very small sample and thus involve less time and difficulties in sampling. Modes of expressing concentrations of atmost pheric contaminants are discussed in Chapter VI (page 150). GASES AND VAPORS I. Methods Giving Quantitative Results in the Field A. EVALUATING THE INTENSITY OF ODOR AND IRRITATION Perhaps the most useful of all methods of detecting and estimating gases ai vapors in the air is by their odors and irritant effects. Only a relatively few tor ones are without either of these characteristics, notable among which is carp monoxide. Many well-informed persons are inclined to scoff at the idea of cj&_ sidering odor and irritation as qualitative guides, much less quantitative ones, p that is either because they have never cultivated and educated the sense of si or because for them that sense is physiologically substandard. The particuja power'of-ffdbl'rttrqmcken-memoryof-aBsociations-has-long-been-recognizedT- instance, the odor of acetamide instantly calls up for most people the associate of mice because it was first met as a constituent of mouse urine; the odor nitrobenzene is associated with shoe polish because it once was widely used-i an ingredjent of shoe polish; and there are many others. ^.i There have been various attempts to describe and classify the odor sensatm Henning,2 in one of the best, recognizes six classes as follows: spicy, flowery, fiffi. resinous (turpentine), foul and scorched. To further divide or add to these'61a|v is a very difficult problem and, even though the memory of an odor may ext over many years, we seem to lack the proper descriptive adjectives. Howey^ regardless of the quality of an odor, Gamble8 has shown that in conformit^p 'IVepr'STla^t'lTe^OTpTreaction'tp'odprs-is'propprtiona'l-to-the-lqgarithm^^s stimulus, that ill, :tne,intensity of sense reaction increases in arithmetical sion as the stimulus increases in geometrical progression. Katz and Allison8 !jd| vised the odor and irritation scales shown in Tables 1 and 2, which with sli modification-have-since proved convenient for other investigators. Odors are best determined by the first and second inhalations, as succeepn "Hans Henning, Der Oeruch. Leipzig, 1624. Eleanor A. M. Gamble, Am. J. Psychol., 10, 82 (1898). *S. H. Katz and V. C. Allison, U. S. But. Mines Tech. Paper No. 267, 1920. SAMPLING AND ANALYSIS OF CONTAMINANTS 175 . Si. Intensity TABLE 1 Scale of Odor Intensities Description i'. H No odor Very faint Faint Easily noticeable Strong Very strong No detectable odor Minimum, but positively perceptible odor Weak odor, readily perceptible Moderate intensity Cogent, forcible odor Intense effect, may irritate TABLE 2 Irritant Scale (Nasal Irritation and Eye Irritation) Intensity Description * |k, *>? Mfe a ffl'' -1 No irritation Faint Moderate .Strong Intolerable Not detectable Just perceptible, not painful Moderate irritation, midway between 1 and 3 Discomforting, painful, but may be endured Exceedingly painful, cannot be endured voluntarily may tend to fatigue the sense of smell. Nasal irritation, throat irritaj|HTitation, however, frequently increase with time, at least for the |||||||conds and sometimes minutes. During the first attempts to evaluate l|i||ation, a subject may have considerable difficulty in making estima- pp||ra-t0-the-pat-tern-of-a-representative-group7-but-mostpersons over` difficulty rapidly so that with a group of six persons the deviation of Swlfo'the average is rarely more than one degree on the scale. As has ^put, however, some individuals are handicapped by having an im^)mell; likewise, temporary impairment of anyone's sense of smell ^^femsivarious causes. Additional published data5-8 on odor intensities |e([ua|p|{;herefore the problem more,or less resolvesdtself into a matter of ^^W^tion, and industrial hygienists find it advantageous to note and ^^gjMqua'lity and intensity of odors wherever an evaluated atmospheric ^^^lrantos-^either encountered or prepared. fmj^teproduced here are portrayals of data collected from experiments fjjtti^S^i^heresrwhereA-toV-investigators-kept-independent-notes.-Each `"j^MIPik-an average of the individual results. Figure d, prepared from the United States Bureau of Mines6 showing the relation beity and concentrations of allyl mercaptan and ethyl mercaptan, JtWBfitical Tables, Vol. I (1926). SfandE. J. Talbot, V. S. Bur. Mines Tech. Paper No. 480, 1930. 8ayers' Yant, S. H. Katz, J. B. Shohan, and R. ^jM^jiograph No. 4, 1931. .roV't lnd W. P. Yant, U. S. Bur. Mines Repl. Invest. No. 2978, 1929. '.-il lIs-