Document 3ez7OLvrznB4ao9K8DppX5BeE

PLAINTIFFS EXHIBIT G-40 1 TV > Fee also inder on jxij/r 3/G ... 20th Annual Safety Equipment Issue Two Sections: Section 1 1; PLANT DESIGN-AND CONSTRUCTION Plan Plants for People. Light for Safer Work. Know Your Floors. .Stuirs. Ramps, Fixed I-adders.*...-.:.... 2. HOUSEKEEPING AND MAINTENANCE * Housekeeping anti Sanitation. Rodent'and Insect Control,. . What Color' Does, Portable-Ladders.' Scaffolds, Work Furnittuv 3. INDUSTRIAL HEALTH ENGINEERING . .. . .. .. ` Ventilation". Washrooms and Lockers, Skin Infections. Heat and Humidity. Controlling Air-Borne Bacteria, Drinking Water.' Food Service ............................................................................................. 4. NOISE CONTROL Measurement of Noise,- Enginccring-Contrdl. Far Defenders'. . Medical Control, Hearing Aids............................................................. Section 2: Service Guide 2.1 5. PERSONAL PROTECTION-PART 1 Eye Conservation. Respiratory Protection. Protection for the Head...Ill 6. PERSONAL PROTECTION-PART 2 Foot Protection. Leg Protection, Safety Clothing. What to Wear, Plastics for Every Purpose. Safety Belts and Harnesses..............151 7. MATERIALS HANDLING -...... ----------- -------- ------ I Fundamentals. Trucks and Tractors. Wire Rope. Chains and Chain-Slings. Fiber Rope;.Hoists and Portable Cranes. Conveyors... .207 8. MACHINE OPERATION AND GUARDING Guarding the Machine. Electrical Equipment, Hand and Power Tools. .231 9. PLANT PROTECTION Fire-Fighting Techniques. Handling Flammable Liquids, First-Aid Extinguishers, Automatic Protection. Spontaneous Ignition. Plant Organization ............................................................................................ 247 10. MEDICAL AND HEALTH SERVICE Medical and Health Service. Care of the Injured. Resuscitation Methods and Equipment...................................................................................279 11. SAFETY PROMOTION AND TRAINING Training and Maintaining Interest, Signs lor Instruction. Direction and Warning. How to Plan Effective Meetings.......................................... 299 Norval Burch. Edltori.il Director. Coun cil Publications Carman Firm. Editor Wiujam R. Vatic. Associate Editor Editorial .......................................................................................................................... 2 Ralph Moses. Art Director Fatalities Up in 1955 ................................................................................................... 5 l(. \V. Champun, Advertising Manager Accident Investigation--D. Paul Cochran ........................................................... 4 ' 4 .* Robot O. Jones. Assistant Advertising Manager Ionizing Radiations--F. A. Van Atta ....................................................................... 6 Oliver Mickila, Advertising Production What's So Special About Women? ........................................................................... 8 Manager The Boy and the Peddler (Diary of a Safety Engineer)--Bill Andrews___ 9 Wire from Washington............................................................................. 10 National Safety News is published monthly by National Safety Council. Copyright 195G bv National Safety Coun cil- Printed In tJS.A. Entered as sec ond class matter June 21. 1921. at the Post Office at Chicago. Illinois, under the act of March 3. 1879. Subscription rate: to members. $5.50 per year, single copies 55 cents; to non-members. $7.30 per year, single copies, 75 cents. Quan tity prices for yearly subscriptions and single issue on request. Member Audit Bureou of Circulation: Indexed in In dustrial Arts Index. Coming Events ............................................................................................................... 61 The Worker's Armor--CarterKendall ...................................................................... 140 The Safety Library ................................................................................................... 147 Is the Purchasing Agent on YourTeam? ..................................................................182 Recognition of a New Industrial Disease--N. Gillmor Long. M.D. and Fred Porter, M.D..............................................................................................184 Falls Have Many Causes ............................................................................................ 191 Voice of the Reader ........................ 274 Personals ................................................................................................... 275 President's Medal Awards ........................................................... .. .270 Safety Films .................................................................................... . ..119 40.0t)0 copies of this issue icere priufe-l. Safety Pesters ........; ......................................... .................................. . ...320 1 tjAfA SHEET CM26 CHECKING..PERFORMAMCEOE LOCAL EXHAUST SYSTEMS Published by the National Safety Council 425 North-Michigdn Ave^, Chicago 11,^111.' -'r*~ 1. Changes in manufacturing' procedures:in the last few years . have resulted in the. use of more toxic materials and in the gener ation of more finely divided par ticles and greater quantities of . smoke' and fume. At; the' same' time, there has been a greater effort to maintain a safe, com fortable atmosphere for the em ployee. 2. It has been estimated that about 80 per cent of the contami nants are controlled by ventila tion, and" today rriafiy 'operations' have ventilation included in the original installation. Although a ventilation system is considered necessary' for safety and comfort on new installations, i -sponsibility for its satisfactory perform ance is seldom assigned to any one individual. Therefore, it frequent ly is not tested when put into op eration and is allowed to become inoperative from lack of mainte nance. ` 3. Excellent handbooks have been written on installation of local exhaust systems, but too little has been ,given on how to maintain them in top operating condition. There are two reasons for this lack of information. 4. First, a local exhaust system usually is not a piece of produc tion equipment. Its maintenance may be slighted in favor of ma chines essential to the manufac turing process. Second, a local exhaust system has a dual aspect. 5. Strictly, it is an engineering or mechanical device, consisting of sheet metal, fans, motors, ar resters, etc., whose performance is specified in terms of rate of air flow, static pressure, rpm. etc. Tfiti' Data Sheet la .one of'4' aerloa published by . th National Safety Counsit, reflecting etperionco from many source*. Not every acceptable safety procedure in the field is nec essarily included*. This.. Date. Sheet ihouU not be confused with Ameri can Standard Safety codes, federal laws, insurance retirements, state lews, rules and regulations, er munic ipal ordinances. This is"icct is the responsibility of the engineer. 6. Yet the basic purpose of a local exhaust system is mainte nance of health or comfort, and sometimes fire prevention. Its effectiveness is measured by how well it removes dust, fume, vapor, or gas that would otherwise make working conditions unsafe or un healthful. This aspect is the con cern of the industrial hygienist, who has been mainly responsible for developing exhaust and dilu tion ventilation for the control of atmospheric contaminants. 7. In the absence of an indus trial hygiene engineer, the safety engineer is usually responsible for the exhaust system. Whenever necessary, he should consult the industrial hygiene personnel of the state health or labor depart ment, of his company's insurance carrier, or of the home office if he is in a plant of a large cor poration. 8. Management should try to develop in the plant engineer greater interest in the principles of local exhaust ventilation. Be cause these systems have been installed for health reasons, the plant engineer may not feel re sponsible 16 r t.Ii c i t-satisfactory; performance. .The safety engineer, on the other hand, who docs have an interest in the safety of work places, is generally unfamiliar with the principles of such sys tems. . 9. Therefore, in ;i plant which docs not have an industrial hy giene engineer, neither the plant engineer nor the safety engineer pays much attention . to ventila tion systems designed for the con- trol of air contaminants. In such a plant, the safety engineer shquld be concerned with the satisfac tory performance of ventilation systems. With the guidance, of outside industrial hygiene engi neers, he can become sufficiently familiar with ventilation equip ment and terminology to check, to some extent, the performance of local exhaust systems. 10. The purpose of this data sheet is to suggest methods by which a local exhaust system can be checked when first put into operation, to determine if it ful fills the specifications, and by which it can be rechecked at in tervals, to determine when, where, and what kind of mainte nance is needed for maximum efficiency. 11. The performance of the system should be the responsibil ity of the plant engineering and maintenance departments. If, as in many cases, this responsibility is not now assigned and the equip ment is not maintained, then it may be well for the safety engi neer to try to interest manage ment in assigning the responsibil ity to the proper people. national Saloty Newt, March, 19S6 11 ity of air in these ducts (hence, air flow in cfm) for different in dustrial processes and industries. *' OI ( l\ '-W -Mtt i These are minimum standards , tbatcraust.he.mot.-Good engineer- . ing practice often calls for even larger air flows than those indi cated in the codes. The engineer should have a copy of state regu lations. Plans for new exhaust systems often have to be approved by the state before installation, andhe should find out if this is the case.injiis state.,------.' : ... ; 21. The engineer should secure a blueprint showing piping layout, C* 0*mt ^o' U m *eT<. K r>cm ' H. *% -(** if possible,.together with data giv- ing the. cfm the designer intended t.o exhaust, from each .hood. For ' nevv systems','-blueprints wil 1 be ' ftgur# I. How to use U-tube (manometer) for measuring lr pressure in ducts. available. For old systems, the plant maintenance or engineering Definition of Terms. . . 12. A local exhaust system is one, that removes an air-borne contaminant, such as dust, fume, vapor, gas, odor, or hot air, as near its source as possible. A gen eral exhaust system, or general ventilation, by contrast, removes air from, the room after the conr. taminnnt has spread. The general exhaust method merely, dilutes the room air by bringing in clean outside air, while the local ex haust traps the material at its source before it is dispersed throughout the room. 13. A hood, is a specially de signed fitting at the entrance of the duct to cause the flow of air to form a pattern that will best control the contaminant It is a partial enclosure around the source where the contaminant is produced, connected with an ex haust duct, usually round sheet- metal pipe, to an exhaust fan. 34. A booth is a hood, usually rectangular or box-shaped, that encloses the operation on the two 1C., Every exhaust fan oper ates by inducing a suction or neg ative pressure in the duct leading from the hood. This means that the air in the duct Is below at mospheric pressure so that room air rushes into the duct This negative pressure is an indication of the air flow, commonly ex pressed in cubic feet of air per minute (efm), that enters .the duct. The negative pressure may be directly related to air flow or, in the case of a plugged duct, in versely related. 17. The negative pressure is easily measured by gauges of var ious types, the basic one being a U-tube or manometer (a piece of glass tubing shaped like a U. the legs being about 8 inches long) half filled with water. A rubber tube from one leg is held at the point where negative pressure is to be measured, and the other leg is left open to the atmosphere (Figure 1). 18. The unit of pressure, which may be positive ("blowing out'') department may not have a draw ing.-. It- is-still-possible. however<- that he can get the layout and . data by writing to the sheet metal company from which his plant bought the equipment. 22. From this material he can determine whether an old system is the same today as it was when - it was-installed, or whether it has suffered the fate of all-loo-many exhaust systems---has had extra branches added or changes made that may now render parts of it less effective. 23. Rare is the exhaust system that does not require understand ing and cooperation on the part of the man who works at the proc ess. Sometimes he has to modify his work habits to permit certain hoods to be used. The engineer should always find out,just how the designer of the system in tended it to be used. The engi neer can often help by seeing that the men know the why of their exhaust systems and know how to use them. , sides, the top and bottom, and the back, with only the front or face open. 15. A collector (arrester) is a device for removing the air-borne material from the air stream. It may be a cyclone or centrifugal collector for large-size particulate material like rough-grinding dust, or a cloth filter for finer dust, or or negative ("sucking in") is inches of water, abbreviated w.g. (water gauge). It is the elevation of one water column above the top of the other. General 19. A good local exhaust sys tem is a well-engineered project, based on precise design data--not Air Samples 24. If the equipment handles silica dust; asbestos fibers, or other toxic materials, such as chromic acid mist, lead fumes or dust, or solvent vapors, the sys tem may be exhausting the "cor rect" volumes of air (according to the blueprint), the fan arid col lector may be in A-l condition-- a water-wash, fog or spray device, electrostatic precipitator, dynamic precipitator, or other type. merely a collection of piping. 20. Many states have codes that specify duct sizes and veloc vet a health hazard rnav still exist. The final and all-iinportant meas ure of whether an exhaust system 12 Ngticncl Sofzty A'ews, fAorch, J956 >. is cqntrollinghazard- is-whether.- tained -involv'e -deUured - ahd ex.*- .that-the.hazard;,Js` still undcr.cdjir Y- the air in the working-region is acting methods for which experi trol. (Cross drafts, as from a man- clean enough to breathe without injury. This question can be an ence and judgment are necessary. In the plant where an industrial cooler, will change the control.) 28. Arranging for air samples swered only by taking air sam- hygienist is employed, the prob and suction tests is the responsi _ pics and analyzing. tl-icrn.. Ig/find.. es m, ,fq]k..-.yuth.in ;}iis.jurisdiction,., bility_^o(._ _jbp . safety ^qnjgineer ^ out if the contaminant is below the maximum allowable limit.* These tests are needed because a person cannot look at a dust cloud or smell toxic vapor and tell if the condition is unsafe. . -. 25. Collection of -arr samples, both in general working areas and 2G. In the absence of a staff industrial hygienist, the safety engineer may obtain the services of the state-bureau of industrial . hygiene (in cither- the health or labor department),"the services of the insurance-carrier or of private consultants. Such services may -rather than the maintenance-en gineer. (It is also frequently con sidered a responsibility of the designer.) ' 20. When the air contaminant is not toxic but causes merely a comfort problem-, .little is gained by air sampling. - .. in ventilation ducts, is a principal__ . also be found in institutes of . in activity of the industrial hygien dustrial health or divisions of in ist. It is. therefore, imperative dustrial hygiene in some- of the Checking the'SysTefn 4. 30. For two reasons, it is well .. that the safety engineer have such medical schools or in schools, of ..to make a complete check of the . personnel secure this information, public-health.: : exhaust system.. First, it can be . Not only .does. the . cqllec'tiop, of...- .-. -27v Onc.e .it, has .been-..deter--., .determined .whetber.it. is meeting,.. samples require exlensive experi- ... mined through air samples that ' specifications for -air volumes, re once, but also the interpretation an exhaust system Is keeping an sistance of ducts, horsepower, of the results and. equally impor exposure within safe limits, the etc. Second, this information will tant, the analytical procedures negative pressure or "suction" in be available for reference when - < from- which .the results aro-ob-* each- branch duct; the'--pressure''- the system recheckedvat later - drop across the collector (if one dates. Most state labor or health depart ments have now incorporated maximum allowable limits in their codes: these limits should be observed. Engineers is. used), and the negative pres sure at the fan inlet may be meas ured. At any future date, if re 31. Some of the measures which will provide the safety engineer, in the absence of an industrial in states -which do not have such limits checks show that these pressure hygienist, with a program for are referred to "Table of Chemical readings are the same and if no checking the performance of a Hazards," Section 41, .Accident Preven tion Manuel for. Industrial. Operations, 3rd- edition '.1955), published" by the National Safety Council. . changes have been made in the process, the hoods, or raw ma terials handled, it can be assumed local exhaust system are dis- cussed below. ; 32. Layout. The safety engineer should get or make a simple line EXHAUST SYSTEM NO.... location....................................... aeion ij mP fwtu ra.'> laro *o ct o cloth | CHECKED BY................. Material hole* tsMnrtd. Att taC'MaftO CuavtC- WKK. wt aaC'ta, 44*3 erw :s- to MtNoic ao <*tu ius to*. o noo cm AT a* 17. 7*30 BAH. drawing showing the layout of each main duct and branch, to gether with the location of the arrester, fan, and motor. He should measure the duct diame ters and note them , on the draw ing. He should also secure the Li open face dimensions of hoods and record them. He should note on the sketch the type and size of & 4* - 3* - , *3 erw * * '/*' 1* ;b *30 C,M `073 CfM !>h-- - fan, motor, drive, and arrester. This drawing need not be elab orate, or even to scale, and can be taken from the drawing of the system mentioned earlier. 33. Test holes should be drilled in each branch. The easiest and Tet Condition of hood and branch (Battered? Removed? Plugged? R*olr3) A S c 0 E r c H i Collector reiiitanee (Jl-(H) Material collected Into tail chock .. Hour* of COMMENTS ! men. and YOUR comment* (use back. If nec*ary): Hood Suction (Inchoc voter) Originally 2.0 Chocked 2.1 2.5 2.0 1.1 2.1 2.2 5.0 .o 3.0 Inlcrvat betvn. teg. thakiaga..........................hrt. cheapest method is to make a 1/16-inch hole, leaving no burrs on the inside of the duct. (See Figure 1.) It is not necessary to cover or plug such a test hole when it is not in use. Sometimes a one-inch length of small cop per tubing or even a small brass petcock is fastened permanently over the hole, but these refine ments are not necessary. Each hole should be circled with a ring Fiqure 2. Salcty dirocfot't 'nspect'on report. of white or yellow paint, and its No"ionoJ %afHy Mar(S, 1956 13 `.Vv. %*:' '****.' -i *- V.` //Jir * ? V W- number or letter painted on the on blast gates. object ;ntl lisiun to h*Nir the pipe duct --the test points fur.- tin: whole system being numbered - 37. Each method has advan tages. If blast gates arc used, /'rim*" showing there is no ;ipprc-. ehhlc settlement of material in it. The.frequency, of periodic .checks . /.serially. ,Qn the sketch,.-each test . - they shcm-ld *b-r 'bolted' -Or -wedded *4 'will'vary with the typo of service hole, with its number, should be after the system is balanced, to performed by the system. Some marked. 34. Balancing the system. Be prevent tampering. Blast gales should not be used on a long, systems will need checkups week ly; others, monthly. fore routine inspections are be complicated system. 40. Interpreting suction pres gun, and even before air samples 3S. A record form (Figure 2) sure readings. Jf the suction pres are taken on a newly installed can be mimeographed for each ' sure at a test hole differs by more . system; the .system must be "bal- ` exhaust system, with a suction than 10 per cent from the original anccd," that is; the proper amount . pressure reading printed for each readings (printed on the report . of air must, be -flowing through__ .. test hole. These readings arc made form f.'-the rcasitmum gSTforatf?-' each hood. Also, in the case of immediately after the system has he figit red/out without difficulty. dust exhaust systems, the air been balanced, arid dust'counts Figure 3 shows how to interpret. velocity in branches and main - (or other air samples) have been ' the U-tubc values. . .. .. ducts must be high- enough to . made ;to show that, the air. con 41. Estimating control velocities . ...prevent.^ettling.of.materia]!,.which .. taminant.bs^undar .control.-. ..... .' or.rvclbcily/ coiltours' /C'ne of.the - ' leads to plugging. ' 3D. Periodic checks.. Each time most important factors is that the 35. In the original design, one the safely engineer makes an in control velocity at the source of of two mean:; of balancing a sys spection. he fills out a report form. the contaminant or the face of the tem is used. The more common He compares the suction pressure .booth j(where the source i,s, inside, - is to provide blast- gates' fdamp- . readings*'ho fihds on rCcheck willv the booth) can he quickly meas ers) in each branch which can the original readings printed on ured by a sensitive direct reading be opened or partially closed so .'the report. He'makes the follow instrument such ns the velomcter that each hood, regardless of ing observations and records the or thermo-anemometer. Where whether it is near the fan or at a results: the source may cover a consider distance, handles its proper amount of air. a. Look at all hoo<ls. See if they arc battered, partially removed, miss able area, the maximum and mini mum should ho indicated. 36. The other method is to size ing. or mangled in any way. 42. Source, location,, direction, - the diameter-of the; branches so ' b. See' if thcmaiuifatturing process and velocity of make-up air. In that more or less air is introduced to serve the same, purpose as blast gates. This must be done before ahd machines have l>ecn altered in any way. Make certain that strong' cross drafts are not- pre venting the air contaminant from addition to the amount and tem perature of the make-up air, its source and method of distribution the system is installed, since once entering the hoo<ls. may be almost as important to the duct work is in, the duct diameters are fixed. Figure 2. adapted from Brandt, Industrial Health Engineering, shows a bal c. Whatever the provision for make up air. make sure that replace ment air has ample opportunity to enter the room. d. Tap the duct at various points successful control of the hazard as the design of the exhaust sys tem itself. Since air blowing out of a duct carries 30 times as far anced system that does not rely with a screwdriver or other metal as the same volume of air mov ing toward a similar exhaust duct 1 (Figure 4), it is very important A, r-1 .-r'"*'*'*' u that the make-up air be diffused in such a way that no disturbing cross currents interfere with proper functioning of the exhaust hood. Frequently, such s. disturb C4M 1 1 i ance can be anticipate! if the essential facts arc noted, and smoke tests may confirm its pres ence. 43. Maintenance orders. When - 1 m * (a* T the system needs mechanical re pairs, such as replacement of worn ducts or hoods, filter clean i 1 !; out, duct cleanout, fan belt ad justment, elc., the safety engineer should see that work orders are (A) Outt rrt!r cr*td plugged, cuting inNtdt cleaning. (S) tncrid riUt<inc or plugging in Kddr pip* or in branch. (C) OaCraaitd fan capacity, opon cUanoul door, or diijointad pip*. (D) Frtf branch ptp partially plugged torrewhere between header and tett hole n.ar hood. (E| First branch pipe partially plugged some where between test hole and iiood lace. (FI Increaied reiiitance due to plugging in header pipe at processed to the maintenance de partment according to the plant's customary procedure. 44. Record filing. The safety engineer should keep a file of his figure 3. How U-tube rtedino* can be jsed to tbow where plugg-ng has occurred. (Cour+cyy "Tenneisen industrial Hygiene Mewj.'' 1950.) inspection reports and reports of air samples. 45. Periodic air samples. If toxic material is handled by the system, in addition to the initial :iir'.<aTiTple$r," thol"1iVtfuKlfi5t hy* 1 gicnist or safely engineer should arrange for periodic samples of the air-borne contaminant in the . workroom. jzn i _ . FAN u------- :o o Blowing ***0'iM*rtL* *o% o ........... ..JO-.O,*.* ,*!**. . I 'f)SUC Jt T I 403 1 f H Inspection by Maintenance Engineer . <000 ' VlkOCltT n 46. The maintenance engineer C0 Of ICtH should check., and .'lubricate- the ..: fan. motor, and drive on schedule, just as he would .any other piece. . of machinery.. If the exhaust ~sys- , tern has any special interlocking... \ V. EXHAUSTING ' Ara<iml[LT (fit jor /ACC VCICCITT AT 0*C Ml - A*AT noa CCMAUCT ll. gates,,jnploivdrb.,ejv.djimpej5;r cnbids, dr ' .he .li6'ei. rtliese`: parts should come under this inspection and should be observed through figure 4. .. Effect ot eir blowing OUT ot A pipe li felt.'meny .feet ewey, but An ejfiAust pipe He* no effect beyond a few inches from pipe end. Thus it cannot "pick up" material unleis pipe and hood are close to the dust source. [Courtesy "Industrial Ventilation--A| Manual of a cycle to assure that they are Recommended Practice.") operating: : ' 47. He should check the inside hood. 11 particles are thrown olT anced" system. instead of relying of the collector with a-flashlight each week, using an access door in the casing. The clean-air side of the collector should be exam by the machine (e.g. a grinder), the hood and the exhaust duct should be placed so that material will be thrown into them. Acces on blast gates, should bo consid ered. Total pressure loss should be calculated carefully, not guessed at. Natural drafts and ined to see that there are no ac sible deanout doors should be cross currents of room air that cumulations of dust, which would mean that the collector was notfunctioning properly. He' should look in the hoppers- to see that : they are not overfilled and should check bag collectors for tom or leaky bags. 48. Wet collectors should be checked for plugged .iray noz zles, plugged drain pi) js, sludge accumulation, and piwpcr water level. 49. Fan speed should be checked monthly with a tachometer. Fan blades and scroll should be exam ined for wear and dirt accumula tion. For this check, a hinged inspection door in the' side of the fan casing or in the outlet duct near the fan discharge is neces sary. Design for Maintenance 50. Good first design will hold down maintenance problems later. 51. Hoods and ducts. The hood should be placed as close to the source cf contamination as pos sible. The source should be en closed if possible, with enough openings left for air to enter. Can opy hoods should be used spar ingly. Too often the operator puls his head between the hood and the contaminant so that he may get an even greater exposure than lie would if there were no provided in ducts, collector, and fan housing.- " 52. Sl eet metal thick enough to ..minimi?.* erosion should be uspd-. For corrosive materials, ducts should lie lined with resistive coat ings or made from suitable corro sion-resistant material. If cort- densalion may be a problem, the need for thermal insulation, "drip" elements, water traps, etc. should be considered. The possi bility of a fire hazard, depending upon the material to be handled,* should also be considered. ` 53. Construction details are of utmost importance: gradual ta pers, bafilcd hoods, wide-sweep elbows, 30 degree angle of entry to main. etc. Design of a "bai- Storufurds jor the Installation of Blotccr arid Exhaust Systems /or Dust. Stock, and Vapor Removal or Convey ing, Pamphlet No. 91. National Fi'o Protection Association and National Bureau of Fire Underwriters. American Standards Association, Z33.1-1950. Although the basic purpose of ven tilating systems is to serve health and comfort, the use of these standards will result in a system which is also of value ftom the fire prevention stand point since it will not transmit smoke anti flame through fire walls anti throughout the premises. The stand ards also provide valuable reference with regard to the other components of the system and related fire extin guishing apparatus. may keep the contamina its from entering the hood should be noted, 'the hood shoulc be ar ranged so that it will interfere as little as possible with the worker, and still be effective. 54. Collectors. The collector should be selected for lie sub stance to be handled, considering such factors as particle size, dust loading, wettability, corrcsion, etc. Thought should be given to com munity air pollution that may re sult if there is no collector or if too much contaminant is exhaust ed to the outside. 55. If. a bag-type filter is se lected: a. Consider size, storage 1 opper ca pacity, free-flowing hoppers. b. Provide a permanent outside lad der and catwalk for easy access: with nonflammable dusts, light the inside of the filter housing for case of inspection. c. Provide a motor-driv ;n shaker rstther than a manually-operated one wherever possible. cl. Provide lime-delay relays and interlocks so that when the fan wheel comes to rest, after the fan motor has been turned off, the shaker motor starts operating and continues for two or tfirec min utes. after which it sto^s and the fan can then be restarted. 56. Fan and motor. jThe fan shouid be put on the jelean-air 'Jniiftoc1 5c^fiv Npwj, Mer<K. 1956 IS side of the collector. When flam and other parts of tho system will mable solid materials or vapors interfere as little as possible with are passed through the system, his work. the provisions of NFPA and -G3.-For testing-exhaust systems NBFU Bulletins No. 91* should visually, smoke tubes are com be followed. r mercially avtiilable (or may be 57. Fan guards and a test hole made by dipping cotton into ti for a tachometer to take speed tanium tetrachloride) . The smoke readings of the fan should be pro given off reveals the path of the vided. Service and inspection air currents as they enter a hood. doors should be placed in the side Smoke tubes are a boon to the of the fan housing, or in ducts at safety engineer. Using them, he the inlet .'ar.d outlet oF-the. fan. . can show the operator how a hood Resistance of the fan discharge" works and thus often convince stack should. .be kept low. A him how important baffles-are, weather rap should be .omitted how necessary -it is to have the wherever possible.-. . hood close to the dust source, and Points on testing;v so on.. - - 64. Two common fallacies need 58. Here are some over-all con clearing up. First, because peo siderations that should be kept in ple can feel air blowing out of an mind in the testing of local ex air line some feet away from the haust Systems." '; ' : end'of.the pipe;'they' think'dusty. 59. ' One of the initial steps that air can be "sucked into" an ex may ;be taken is to ensure that haust hood from several feet outside vendors or contractors away. It cannot. Air can be provide a meaningful guarantee "sucked" only 1/30 the distance it of performance for their equip can be blown (Figure 4). In ex ment or system. Then the vendor hausting, the air velocity at a dis is made responsible for equip tance of one diameter from the ment or.'systems' 'which do not pipe end: is about 10 per cent of perform properly. the velocity in the pipe; in blow 60. Many- a good exhaust sys- ing, this 10 . per ; cent figure is tern has been overloaded and reached 30 diameters from the made ineffective .by the addition pipe. of hoods in later years. Before 65. Suppose, for example, that hoods are added, it should be a pipe 6 inches in diameter has ascertained that the present air traveling through it at a ve equipment can handle the addi locity of 4,000 feet per minute. tional air flow which will be Six inches from the "sucking" needed without robbing the ex end, the air velocity will be 400 isting hoods. feet per minute (hardly detect 61. Make-up air is sometimes a able by feel); at the blowing end. bigger problem than the exhaust the 400 fpm velocity is reached system itself. Provision should some 15 feet from the end of the be made for the air to get into pipe. the room to replace the air ex 66. A second fallacy is that hausted. In winter the make-up downdraft ventilation or hoods at air may have to be tempered. A floor level are required because room should never be closed up organic solvent vapors, like ben tight and "air bound." zene (benzol), trichloroethylene, 62. The man on the job must carbon tetrachloride, and the like, know the reason for the exhaust are heavier than air. Heavy gases system and must understand how introduced into air tend to fall to use it. Better yet, the safety before they become mixed with engineer should consult with him the air. Thus, a vapor train of before the installation is made, to pure gasoline can form and travel make sure that hoods, enclosures, along the floor many feet. 67. However, as vapors are giv Bulletin No. 91, Blower and Exhaust en off from industrial processes, Systems, National Fire Protection As sociation, 0 Batterymarch St, Boston 10. Bulletin No. 91, Exhaust Systems for Dust, Slock, and Vapor Removal, National Board of Fire Underwriters, 80 John St., New York. the atmosphere contains not pure vapor, but a mixture of vapor and air. Even air saturated with the vapor remains saturated for a very short time: it soon becomes diluted with more air because of random convection and wind cur rent in the room. -68. A concentration of 1,000 parts per million of benzene, which is 25 times the maximum allowable health limit, is only 1.0017 limes as heavy ;is air (al though pure benzene vapor is three times as heavy as air). That is, the ratio of weight o? air to weight of the benzene-aix mixture is only 1.00 to 10Q,17y-Ihcre c.ouIdn never be any sinking or stratify ing of even this dense. (1,0.00 parts per million) benzene concentra tion. Consequently, a side or back hood wo.uld.be..just.as effective as: a'downdraft hood. " . REFERENCES Perhaps the best .technical reference not' only-'for design 'of' exhatlst systems; but also for checking of them, is: In dustrial Ventilation--A Manual of Rec ommended Practice, published by the American Conference of Governmental Industrial Hygienists (3rd ed., 1954), available from the Committee on In dustrial Ventilation, P. O. Box 453. Lansing, Mich. . The following give information on design of exhaust systems for various processes, as well as information on the toxicity of industrial materials: . Accident Prevention Manual for In dustrial Operations, National Safety Council, 3rd Edition. (1955). Industrial Health Engineering, Allen D. Brandt. John Wiley & Sons, Inc. Heating, Ventilating, Air Condition ing Guide, The American Society of Heating and Air Conditioning Engi neers (published annually). Plant Process Ventilation, W. C. L. Hcmcon, Industrial Press, 1955 edition. Industrial Dust. Drinker and Hatch. 2nd edition (1954). Excellent references for fire preven tion considerations are listed below: Flammable Liquids and Gases, Vol. I: Combustible Solids, Dusts. Chemi cals and Explosives. Vol. II, National Fire Codes, 1955. National Fire Pro tection Association. ACKNOWLEDGMENT The original draft of this data sheet was prepared by Willis G. Hazard. Owens-Illinois, as a project of the Health Maintenance Committee of the Automotive and Machine Shop Section. National Safety Council. A second draft was prepared by Frank A. Patty, Gen eral Motors Corporation, with approval of Mr. Hazard. This publication has been reviewed by members of the Na tional Safety Council and representa tives of chapters of the American So ciety of Safety Engineers. It has been approved for publication by the Publi cations Committee of the Council's In dustrial Conference. 16 .Vabono/ Safely Newt, Marsh, 1956