Document bO0GDX6XqL3E3yvO3E60b39LO

FILE NAME: BF Goodrich (BFG) DATE: 1965 July DOC#: BFG031 DOCUMENT DESCRIPTION: Journal Article - Various Methods of Controlling In Plant Inhalable Contaminants Various Methods O f Controlling In-Plant Inhalable Contaminants After identifying contam inants and deter mining exposure severity, article tells how to control contam inants within the plant by William E. McCormick Mgr., Dept, of Industrial Hygiene and Toxicology B. F. Goodrich Company PROVIDING A HEALTHFUL working environment for em ployees has long been an accepted fact of American indus mospheric contaminant may ap pear to present little or no prob lem. After all, we should know what is being used and, therefore, toxicologist. With the knowledge so developed, materials can be put into industrial use and reasonably reliable controls established. In try. It is also accepted that the immediate identity can be made. general, these uses occur only responsibility for providing this is Actually, this first phase of our after adequate factors of safety that of management. As a result four-part effort is often the most have been "built into" the controls of this recognition, industrial difficult. Identity is relatively and after careful regimens of hygiene personnel have become simple if a single compound, with medical observance of exposed necessary adjuncts to most corpo no resulting chemical reactions, is personnel have resulted. rate management staffs, and it the contaminant. However, with 3. The severity of the exposure becomes the primary function of multiple compounds, some or all of must be quantitated. Whether a these personnel to provide the which may react--or with com contaminant is a hazard to health many skills needed in the control pounds producing decomposition or well-being can only be deter l of in-plant contaminants. products--the problem becomes mined after adequate evaluations Because of the extent of the extensive and perhaps insurmount of the working environment have problem of "in-plant contami able. Years of time and millions been made to provide a sound basis nants" some restriction of the of dollars have been expended in for judgment. These evaluations subject is necessary. Consequently, attempts to accurately identify the may be relatively simple or quite this article shall be confined to contaminant(s) in smog, notably complex, depending upon the 1 inhalable contaminants only; i.e., that occurring in Los Angeles, but material(s) involved and the man | gases, vapors, dusts, fumes, mists. without complete success. Many ner of use. They may require only Is the Contaminant Hazardous? examples of in-plant problems of similar complexity can be cited, the simple use of direct reading instruments in the hands of a In our attempts to define and requiring the best analytical skills skilled technician, or they may tax elucidate the problem of in-plant and tools for their solution. the ingenuity of several scientific , contaminate control, we need to be 2. Some knowledge about the disciplines, possessing highly re particularly aware of this basic 'physiological effect(s) of the con fined techniques. In any event, philosophy : atmospheric contami- taminant must exist. To be most they must be so designed as to fcants are ever present and whether meaningful, this should be data represent actual conditions of control is needed must be deter gained from wide experience with exposure on both a severity and a mined on an individual problem I basis. humans. Often this is unlikely or impossible, particularly with mate time basis. Many commercial devices are For in-plant operation, the ques rials of new or recent origin. now available to assist the indus tion must always be answered on the basis of degree of exposure---- Therefore, certain compromises have to he made. Reliable data, trial hygienist in these efforts. Let no one assume, however, th a t 18 there "too much?" Is there a derived from animal experimenta these devices can be used indis hazard to health or well-being? | In order to answer these questions, tion, and properly interpreted, can be very useful in providing sound criminately, or by untrained per sonnel. Many of them are simple 1 fur things must first be done: bases for judgment on the ex to use, but adequate training on I. The contaminant must be pected effects on humans. This is the part of the evaluator must identified. The identity of the at- the function of the industrial exist in order that time exposure ENGINEERING, JULY, 1965 13 conditions are simulated, as well as the realization of the device's limitations. h- The results of the quantita tion must he interpreted. Reference tas been made earlier to one of the basic tenets of industrial hy giene: the decision regarding the existence of a hazard, rests not on the basis of the presence or ab sence of a contaminant, but, rather, on the quantity and time of ex posure to it. The presence of some atmos pheric contamination is a practical necessity, not only of all industrial operations, but of all everyday living. It becomes simply a matter of deciding whether the exposure to which a human is subjected is "too much" without affecting his health or well-being. Fortunately, relatively good guidelines have been developed through research and experience whereby this judgment can be made for a large number of mate rials. These guidelines are referred to under various names: maximum allowable (or sometimes accep table) concentrations, hygienic standards, threshold limit values. These terms may or may not be synonymous. The values most widely in use today are those pub lished annually by the American Conference of Governmental In dustrial Hygienists and are sug gested maxima for eight-hour, five-day week exposure on a timeweighted basis. Some of the more common values are shown in Tables I and II. It should be appreciated that these values are suggested guides and are not intended as hard and fast boundaries between "hazard" and "no hazard." Sound profes sional judgment is needed in their interpretation. Unfortunately, many previous TLV's of the ACGIH have been transferred into governmental codes and have be come "legal" values. The use of a single value as a guideline leaves much to be de sired. For this reason, the Ameri can Standards Association has recently reactivated its Z 37 Sec tional Committee to develop stand ards of safe atmospheric exposure. These will be multiple values and will fill a long-felt need. Regard less, however, of the value used, or its source, the proper interpre tation of it and the assessment of the severity of hazard requires professional industrial hygiene knowledge. How Can the Contaminant Be Controlled? Four basic methods exist for the control of atmospheric contami nants. It is not unusual to use two or more in combination. 1. Replacement or substitution: frequently, a less hazardous mate rial may be used. For instance, the insiduous health hazards of benzene and carbon tetrachloride are well known. Because of this, their use as industrial-type sol vents has been supplanted to a large degree by less hazardous ones--particularly, by toluene and methyl chloroform, respectively. Obviously, the degree to which this method of control can be used is determined by chemical and physi cal requirements, fire hazards, costs, etc. and although it is one of the less widely applicable con trol methods, it should always be considered. 2. Enclosure or isolation: this method of control is widely used, especially in the chemical and petroleum industries. An example of it is reactors used in the manu facture of SBR polymer. The method has wide application and enables industrial handling of a great number of hazardous mate rials. 3. Ventilation: perhaps the most widely practiced method of control is the use of ventilation. This may be of two basic types: general (provided by natural or mechani cal means) and process (in nearly all cases requiring the use of mechanical air-moving equipment). The literature is extensive on the design techniques of process ventilation, both in a general way and for specific industrial opera tion. In spite of this, it is often poorly designed and fails to accom plish the required control, or if it does, at greater cost than it should. From the standpoint of costs, it is poor business to over design. All air exhausted must, of course, be replaced, and heat losses, especially in northern cli mates, become significant. As an example, approximately 450 Btu are lost for each 1000 cu. ft. of air, with removal at 70 F and makeup at 40" F, SOX rh. If we assume a heating cost of 60 cents per million Btu, the exhausting of each 1000 cfm over a 24-hour period will cost 40 cents. Correct design becomes, therefore, doubly important: for adequate control and lowest cost. General ventilating, whether it be produced by natural draft through room openings or from mechanically driven fans, has limited use for industrial hazards. It can only be used with con taminants of low hazard and where good air mixing of the working area can be attained. Considerably more air must be removed than with local process ventilation, although the initial cost of the equipment for general ventilation is usually considerably less. An approximation of the amount of general ventilation re quired for a volatile solvent can be calculated from the equation: V = Where V = W = M = C = 6.45 W --------- X 10" MC volume in cfm weight, in pounds per hour, of solvent lost by evaporation molecular weight of solvent TLV of solvent in ppm 4. Personal protective equip ment: there is available today a wide variety of well-designed equip ment, to be worn by the individual, for protection against hazards to or via the respiratory organs. These devices are an important ABOUT THE AUTHOR William E. McCormick received his B.S. and M.S. degrees in physical chemistry from Pennsylvania State University. Prior to establishing the Dept, of Industrial Hygiene and Toxi cology at The B. W F. Goodrich Co. in 1946, Mr. McCor V mick served as an industrial hygien ist for the U. S. Public Health Service and the Georgia State Health Dept. Earlier, he was engaged in development and research activities pertaining t0 respiratory protective devices f r Willson Products Co., Inc. Su Ar Be Ca Ch Le Le \L Mt Ni Ti means Their p in diso use. Th in prov wide m emerge: posure. special of the practice can onl combine tective tion oi circums wearing ( 14 AIR ENGINEERING, JULY, 1965 r .AIR Table I-- TLV-- Dusts Toxic Mineral Substance Mg/M3* Substance m.p.p.c.f.** Antimony ( as Sb ) 0.5 250 Beryllium Cadmium oxide fume 0.002 Silica, crystalline quartz 0.1 %Si0,, + 5 Chromic acid and chromates (as Cr03) 0.1 Silica, amorphous, Lead 0.2 including diatomaceous earth 20 Lead Arsenate 0.15 Asbestos 5 Magnesium oxide fume 15. Mica 20 Mercury 0.1 Soapstone 20 Nicotine 0.5 Talc 20 Titanium dioxide 15. *M illigram s p e r cubic m eter of a ir. **M illio n particles p er cubic foot of a ir. means of contaminant control. Their principal disadvantage lies in discomfort through prolonged use. They find their greatest asset in providing protection against a wide number of materials during emergency-type, or short-term ex posure. Of course, there are a few special situations where, because of the high degree of hazard, practical control of a contaminant can only be achieved through the combined use of respiratory pro tective devices and either ventila tion or enclosure, and in these circumstances their continuous wearing is necessary7. To be assured that the quality of the respiratory protective de vice is satisfactory, only those bearing the seal of approval of the U.S. Bureau of Mines should be used. It is, of course, elemental that the correct type of device for the specific hazard be selected, that it be fitted properly, and that it be satisfactorily maintained. Need for Professional Know-How The control of industrial air contaminants is a complex proce dure, requiring the skills of many disciplines. It is paramount that personnel, properly trained in these disciplines, make the judg ments required, which become in a very real sense, judgments deal ing with the lives of humans. Industrial hygiene holds that any material can be used in indus try--the only problem is to devise the necessary controls for its safe use. Article originally presented by the author on March 9, 1965 at the Industrial, Commercial and Institu tional Building Conference held in Detroit, Michigan. Table II-- TLV-- Vapors Substance Acetone Acrylonitrile Ammonia Aniline C Benzene Butadiene 2-Butanone (methyl ethyl kitone) Carbon disulfide Carbon monoxide Carbon tetrachloride Chlorine 1, 2 Dichloroctliane (ethylene dichloride) Ethyl acetate Ethyl alcohol Ethyl bromide Fluorine C Formaldehyde Gasoline Heptane (n-) Hexane (n-) Hydrogen bromide Hydrogen chloride C Iodine ppm* 1000 20 50 5 25 1000 200 20 100 10 1 50 400 1000 200 0.1 5 500 500 500 3 5 0.1 Substance Isophorone Methyl acrylate Methyl alcohol Methyl chloroform (1, 1, 1, trichlorocthane) Methylene chloride Naphtha (petroleum) Nitrobenzene Nitrogen dioxide Ozone Perchloroethylene Phenol Prophyl alcohol (iso-) Propylene dichloride (1, 2 dichloropropane) Stoddard solvent Sulfur dioxide T etrahy drofuran Tolune T richloroethy lene Turpentine ! Vinyl chloride Xylene *P a rts of su b stan ce p e r m illion p a rts of air. N ote: * indicates ceiling ra th e r th an tim e -u e ig h te d values. ppm 25 10 200 350 500 500 1 5 0 .1 100 5 400 75 500 5 200 200 100 100 500 200 ENGINEERING, JULY, 1965