Local Exhaust Systems Control ot Hazardous Processes Role of the safety professional Local Exhaust Systems Parts of a local exhaust system Hoods Ducts Air cleaners--general Air cleaner efficiency Dust arresters Air cleaners for radioactive dusts Air cleaners for fumes and smokes Air cleaners for gases and vapors Fans Fire prevention considerations Checking performance Exhausts for Special Operations Open-surface tanks Spray booths Fume control for electric welding Dust control in foundries Grinding operations Woodworking Cast iron machining Oil mist Melting furnaces Materials conveying Internal combustion engine ventilation Fog removal Kitchen range hoods Recirculation of "cleaned" air References Chapter 29 S52 854 881 894 851

Local Exhaust System useful material is held to a minimum (Fig 29-19) Internal combustion engine ventilation Gasoline, diesel, and natural gas engines are being used in increasing numbers and sizes inside factory buildings They are run not only in garages, where maintenance checks and repairs are made, but also in ware houses, storage spaces, loading docks, aisleways, and other indoor areas They are being used as drives for air conditioning and electric generating equipment Their products of combustion contain toxic materials alde hydes, carbon monoxide, and nitrogen oxides The threshold limit for aldehydes in air is only 5 parts per million (ppm) They may be generated if the engine is m poor operating condition, is burning oil, or has a smoky ex haust Usually, however, they are of less importance, from the industrial hygiene standpoint, than the carbon monoxide re leased For an 8-hour exposure, the permissible limit of carbon monoxide gas in air is 50 ppm, but a ventilating system should be designed to keep a much lower level of carbon mon oxide (CO) This value should not be over 250 ppm of CO for one hour's exposure Exhaust gases as released from a gasoline engine contain from 1 to over 10 per cent CO (1 per cent = 10,000 ppm) If the engine is operating at full rated horsepower, its exhaust gases will contain about 3 per cent CO When idling, they may contain over 10 per cent Gasoline engines are built m many sizes, ranging from fractional to more than 200 hp Lift trucks commonly have a maximum delivery of 35 to 50 hp Since the engine normally discharges about one cubic foot per minute of exhaust gases per operating horse power, a lift truck when operating near its maximum rated horsepower would release 0 03 times 50 or 1 5 cfm CO The quantity of fresh air that would be needed to dilute this CO output so the concentration would be be low the threshold limit value would depend on many factors (See "References" at end of this chapter Dept of National Health and Welfare, Michigan Health Department, and Milton Shembaum) Fully as important as the ventilation rate is the distribution of the incoming fresh air throughout the building A warehouse, for example, may have a central runway, with ware piled on each side in bays Dead-end alleys or aisles may lead into these bays and sometimes these constitute stagnant pockets The CO concentration may build up to exces sive levels m an aisle when a truck is doing a stacking operation there, and still be negli gible along the central runway Such a situa tion can best be solved by introducing the fresh air by a duct having discharge grilles m the pocketed regions, rather than along the central runway The latter generally receives adequate ventilation from the building doors Improvement is sometimes made by ex tending the tailpipe of a warehouse truck up ward so it discharges vertically at a point above the operator's head This solution is effective, too, m a situation where a dump truck backs up to a pit hopper, at the bottom of which there may be a conveyor Some times a man stands across the pit where the conveyor controls are located and he can get the full blast of the truck exhaust A vertical discharge pipe would prevent this There are areas where it may not be prac tical or economical to ventilate for the preven tion of objectionable concentrations of CO -- such an area is frozen food storage rooms Electric trucks are recommended for these areas Finally, there is the garage which has fixed automobile repair stations Here the answer is a local exhaust system Three-inch flexible ducts are fitted over the tailpipes The flex ible ducts join 4-m branches, which in turn are connected to a header located below floor level or overhead Exhaust requirements are shown in Table 29-G The fan should be capable of exhausting the required air volume at l'/ in static pres sure, water gauge For general garage ventilation, where cars are in motion or are idling outside of the re pair stall, the following ventilation should be provided to dilute the carbon monoxide Per running auto--5,000 cfm, Per running truck --10,000 cfm (or more),' Per horsepower for diesel--75 cfm Air sampling.

tion The danger is particularly great in hot weather when he is sweaty He should develop the habit of keeping his body insulated from both the work and the metal electrode and holder He should never permit the bare metal part of an elec trode, the electrode insulation, or any metal part of the electrode holder to touch either his bare skin or any wet covering on his body Consistent use of well insulated electrode holders and cables, dry clothing on the hands and body, and insulation from ground will be helpful in preventing contact Some specific precautions for prevention of electnc shock are 1 In confined places, cover or arrange cables to prevent contact with falling sparks 2 Never change electrodes with bare hands or wet gloves, or when standing on wet floors or grounded surfaces 3 Ground the frames of welding units, port able or stationary, m accordance with the National Electrical Code With a small welding unit, a primary cable containing an extra conductor, one end of which is attached to the frame of the welding unit, can be used By means of the proper po larized plug, this ground connection can be earned back to the permanently grounded connection in the receptacle of the power supply 4 Arrange receptacles of power cables for portable welding units so that it is impos sible to remove the plug without opening the power supply switch, or use plugs and receptacles which have been approved to break full load circuits of the unit 5 If a cable (either work lead or electrode lead) becomes wom, exposing bare con ductors, cover the exposed portion with rubber, plastic, or friction tape equivalent to the cable covenng 6 Keep welding cables dry and free of grease and oil to prevent premature breakdown of the insulation 7 Suspend cables on substantial overhead supports if the cables must be run some distance from the welding unit Protect cables that must be laid on the floor or ground so that they will not interfere with safe passage or become damaged or en tangled 8 Take special care to keep welding cables away from power supply cables or hightension wires Gas-shielded arc welding Gas-shielded arc welding (Fig 31-8) is used for joining all types of metals and cast ings In gas-shielded methods, only one electrode is used A gas or gas mixture is in troduced through the torch to surround the electrode and the welding point like a shield The gas cone protects the molten weld pud dle from the atmosphere and stops oxidation of the base metal The electrode conducts either alternating or direct current to provide heat Tungsten arc In gas-shielded tungsten arc welding, the electrode does not melt and is not used for filler metal The electrode is tungsten, which is highly resistant to heat and non-consumable m the welding process Metal arc.

Welding and Cutting TABLE 31-B FILTER LENS SHADE NUMBERS FOR VARIOUS WELDING AND CUTTING OPERATIONS (WELDER AND HELPERS) Type of Operation Recommended Shade Number Resistance welding, and for protection against stray light from nearby welding and cutting (if persons are out of the danger zone) Clear or filters up to No 2 Torch brazing or soldering 3 to 4 Light oxygen cutting and gas welding (to '/a in ) 4 or 5 Oxygen cutting, medium gas welding (Vs to 'A in ) and arc welding up to 30 amps 5 or 6 Heavy gas welding (over '/* in) and arc welding and cutting from 30 to 75 amps 6 or 8 Arc welding and cutting from 75 to 200 amps 10 Arc welding and cutting from 200 to 400 amps 12 Arc welding and cutting exceeding 400 amps 14 NOTE Flash goggles should be worn under all arc welding helmets particularly for gas-shielded metal arc welding Adapted from Welding Handbook, 5th ed American Welding Society items should conform to ASI Standard Z2 1, Safety Code for Head, Eye, and Respiratory Protection Table 31-B is a guide for select ing the correct filter lens for various welding and cutting operations Goggles or spec tacles should have side shields Guidance for lens care is given in Chapter 38, "Personal Protective Equipment " Protective clothing Some of the items of protective clothing needed by welders (Fig 31-12) are 1 Flame-resistant gauntlet gloves, except on very light work 2 Aprons of leather, asbestos, or other flameresistant material to withstand radiated heat and sparks 3 For heavy work, fire-resistant leggings, high boots, or similar protection 4 Safety shoes, wherever heavy objects are handled Low-cut shoes with unprotected tops should not be used because of the spark hazard 5 For overhead work, capes or shoulder covers of leather or other suitable mate rial Skull caps of leather or flame-resistant fabric may be worn under helmets to prevent head bums Also, for overhead welding, ear protection (wool or rubber plugs or wire screen protectors) is some times desirable 6 Safety hats or other head protection against sharp or heavy falling objects Operators and other persons working with inert-gas shielded arc welding should keep all parts of the body which could be exposed to the ultraviolet and infrared radiation covered to protect against skin bums and other types of injuries Dark clothing, partic ularly a dark shirt, is preferable to lightcolored clothing in order to reduce reflection to the operator's face underneath the helmet Cotton clothing disintegrates m from one day to two weeks, presumably because of the high ultraviolet radiation from arc welding and cutting Wool or leather clothing, there fore, is preferable to cotton because it is more resistant to deterioration For gas-shielded arc welding, woolen cloth ing is also preferable to cotton It is not readily ignited and protects the welder from changes m temperature Cotton clothing, if used, should be chemically treated to reduce flammabilitv In either case, clothing should be thick enough to keep radiation from pene trating it Outer clothing should be reasonably free from oil and grease Sleeves and collars should be kept buttoned Aprons and overalls should have no pockets, in which sparks could be caught, on the front of them For the same reason, trousers or overalls should not have tumed-up cuffs 944

TABLE 33-B HUMAN RESISTANCE TO ELECTRICAL CURRENT Body Area Resistance (ohms) Dry skin Wet skin Internal body--hand to foot Ear to ear 100,000 to 600,000 1,000 400 to 600 (about) 100 flow, it is measured in ohms Low VOLTAGE is a rather ambiguous term depending upon whether it is being used by a safety engineer, a plant electrician, ora line man For the purposes of this chapter, low voltage is 24 to 600 volts, and "safety" low voltage refers to voltages below 24 volts Electrical Injuries Current flow is the factor that causes injury in electric shock, that is, the seventy of electnc shock is determined by the amount of current flow through the victim (Table 33-A) Expenmental and field data from authontative sources (see references for articles wntten by Charles F Dalziel) indicate that, m general, an alternating current of 100 milliamperes at commercial frequency (60 hz) may be fatal if it passes through the vital organs Similarly, it is estimated that a value of 16 milliamperes is the average current at which an individual can still release himself from an object held by the hand Such current flow may readily be obtained on contact with low-voltage sources of the ordinary lighting or power circuit Because current flow depends on voltage and resistance, these factors are important Other factors affecting the amount of damage done are the parts of the body involved, the duration of current flow through the victim, and the frequency (if alternating current) Resistance to current flow is mainly to be found m the skin surface Callous or dry skin has a fairly high resistance, but a sharp decrease m resistance takes place when the skin is moist (Table 33-B) Once the skin resistance is broken down, the current flows readily through the blood and body tissues Whatever protection is offered by skin re sistance decreases rapidly with increase m voltage High voltage alternating current of 60 Hz causes violent muscular contraction, often so severe that the victim is thrown clear of the circuit Although low voltage also results m mus cular contraction, the effect is not so violent The fact, however, that low voltage often pre vents the victim from freeing himself from the circuit makes exposure to it dangerous Death or injury by electric shock may re sult from the following effects of current on the body 1 Contraction of the chest muscles, which may interfere with breathing to such an extent that death will result from asphyxia tion when the exposure is prolonged 2 Temporary paralysis of the nerve center, which may result in failure of respiration, a condition which often conbnues until long after the vicbm is freed from the cir cuit 3 Interference with normal rhythm of the heart, causing ventricular fibnllabon In this condibon the fibers of the heart mus cles, instead of contrachng in a coordi nated manner, contract separately and at different bmes Blood circulabon ceases and death ensues, since apparently the heart cannot spontaneously recover from this condition It has been esbmated that 100 milliamperes is sufficient to cause ventricular fibnllabon 4 Suspension of heart acbon by muscular contraction (on contact with heavy cur rent) In this case the heart may resume its normal rhythm when the vicbm is freed from the circuit 5 Hemorrhages and destruction of bssues, nerves, and muscles from heat due to heavy current In general, the longer the current flows through the body, the more serious may be the result Considerable current is likely to flow from high-voltage sources, and in gen- 977

standing to windward A cover should be removed with the man facing the dome With feet well braced, he should use short, vigorous pushes on the bar The cover (if not provided with a chain) and loose tools should be removed to the walk platform or other safe place so that they will not fall On the bolted type of dome cover, all nuts should be unscrewed one turn and the cover lifted to break adhesion which may exist between the cover and the dome ring If there is a sound of escaping vapors, the dome should be tightened and the venting operation repeated All dirt, cinders, and debris should be re moved from around the interior type of dome cover before the yoke is unscrewed When the car must be unloaded through the bottom outlet valve, dome covers should be adjusted to allow for venting The screw type should be screwed down just enough to ex pose the Vfc-m vent holes m the threaded por tion of the cover A small, thin wood block should be placed under the bolted type of cover, and the in terior type of dome cover should be tightened up in the yoke to within VS> in of the closed position An asbestos or metal cover or wet burlap or canvas should be placed over the tank manhole to protect against entrance of sparks or other source of ignition Unloading and loading connections The safest method of unloading tank cars is through the dome Some states prohibit bottom unloading Where a car has only bot tom unloading, the tank's outlet valve must be closed before the outlet chamber cap or plug is removed A pail or tub should be placed under the outlet chamber and the 2-m outlet cap unscrewed The condition of the outlet valve should be checked, and if there is no senous leak, the unloading should proceed If the plug does not loosen readilv with a 48-inch wrench, the bottom outlet cap or plug can be tapped to loosen it If the valve leaks so badly that a connection cannot be made without spilling the product, the car should be unloaded from the top In cold weather the outlet chamber, if the chamber or valve is frozen or blocked with frozen liquid, should be carefully examined for cracks If a crack is not found, the con nection for unloading should be made and the outlet chamber wrapped with burlap or other rags, and hot water or steam applied The connection from the car to the storage tank should be carefully checked for proper condition before the car valve is opened The storage tank should be watched to pre vent overflow, and the hose and unloading line should be checked frequently The tank car should be examined before loading lines are disconnected to make certain that it is completely empty A workman should be present throughout the entire loading or unloading operation and while a car is connected If it is neces sary to discontinue operations before they are completed, the outlet valve should be closed and the dome cover and outlet chamber cap replaced Tank cars should not be allowed to stand with loading or unloading connections at tached after operations are completed If flammable liquids are spilled, spill areas should be covered with fresh dry sand or dirt Never flush spills into public sewers and drainage systems, or natural waterways When heater pipes are used for unloading, the steam should be applied slowly until it begins to exhaust at the outlet pipe Steam pressure should not exceed that needed to bring the contents to the desired tempera ture and should never be high enough to cause the contents to overflow Care also must be exercised to avoid ex ceeding the flash temperature of "cut-backs" or additives introduced into various heavy products --for example, the addition of naph tha to residual asphalt Overheating these products containing certain additives can release dangerous quantities of flammable vapors Placards Shipping cards and Dangerous or Flam mable placards should be provided and then removed after operations are completed They should then be replaced with DANGER OUS-EMPTY placards Defect cards or forms of any kind which have been attached to a car by railroad employees should not be removed Placards, rags, waste, and blocks should not be disposed of in the tank or car body 1023

Fir 36-9 -- Proportioner permits operator to varv percentage of foam-producing concentrate are listed by Underwriters' Laboratories, Inc , are siphoned through a proportioner at rates not exceeding 2 per cent by volume The reflective white opaque surface formed by the air bubbles and wet-water particles makes this agent a good medium for protec tion from exposure fires The cellular struc ture of the foam also retards heat conduction, thus affording insulation As the foam blanket absorbs the heat and breaks down, the wet water released from the air bubbles car ries the heat away from the protected surface Mixing wetting agents with other wetting agents or with mechanical or chemical foam is not recommended, since it may neutralize the effect of the agents and thus destroy the fire fighting properties High expansion foam, using wetting agents in ratios as high as 1000 to 1, has been devel oped These foams have a water content ranging from 0 2 to 10 oz/cu ft, and are effec tive in fighting fires in inaccessible places, such as coal mines and building basements High expansion foams can also be used in total flooding systems designed to fill en closed spaces, such as rooms or buildings The systems are suitable for hazards involv ing flammable liquids and ordinary combus tibles, if properly designed for the specific hazard and area Wet water The wet water principle can also be used without generating foam In liquid form, wet water has the same general extinguishing properties as plain water However, its cool ing ability is increased, and there is a greater penetration of porous surfaces because of its reduced surface tension Carbon dioxide extinguishing systems Fixed (local or flood-type) C02 systems are often installed for the protection of rooms that contain electrical equipment, flammable liquid or gas processes, dry cleaning machin ery, and other exposures where fire can be ex tinguished by diluting the oxygen content of the air or where water must not be used be cause of electrical hazard or the nature of the 1089

Personal Protective Equipment lions Satisfactory performance specifica tions exist for certain types of personal protective equipment, notably safety hats, devices to protect the eyes from impact and from harmful radiations, and rubber insulat ing gloves, but there are no approving lab oratories to test equipment regularly accord ing to these specifications Unless the safety professional has ample testing facilities available to him, he must rely upon the equipment manufacturers' endorsement for devices that may fill his needs Fortunately, the manufacturers have been aware of their responsibility in this re spect, and have a remarkable record of re liability Their representatives can usually Be called in to demonstrate their products and discuss their conformance to safety stand ards The succeeding pages discuss seven major areas of personal protective equipment-- head, eyes and face, ear, respiratory, hands, feet, and body Each section will provide the latest information on the standards avail able or proposed, some details about the equipment available, suggestions for select ing equipment to meet the job hazard, and some case histones in the development and use of specific devices Use equipment property The next problem is that of having work ers wear personal protective equipment, once it has been chosen Several factors influ ence the solution of this problem Among them are (a) the extent to which the men who must wear the equipment understand its necessity, (b) the ease and comfort with which it can be worn with a minimum of interference with normal work procedures, and (c) the available economic, social, and disciplinary sanctions which can be used to influence the attitudes of the men In an organization where workers are ac customed to weanng personal protective equipment as a condition of employment, this problem is minor The men are simply issued equipment which meets the require ments of the job and is easy to wear, and are taught how and why it must be used There after, periodic checks are made until use of the issued equipment has become a matter of habit with the workers When a group of men are issued personal protective equipment for the first time or when new devices are introduced, the prob lem may be more difficult The men will need to be given a clear and reasonable explanabon as to why the equipment must be worn Traditional work procedures may have to be changed If such changes are required, a good deal of resistance, justifiable or not, may be generated Also, workers may be reluctant to use the equipment because of bravado or vanity The practice of having supervisors and foremen try out new protective equipment and devices prior to actual adoption, and getting their comments and discussing the advantages, has been successfully used m many operations A good deal of the resistance to change can be overcome if the men are allowed to choose the particular style of equipment they will wear from a group of different styles which have been preselected to meet the job re quirements In some situations, it may be advisable to have a committee from the work force help select suitable devices Manage ment's desire to standardize on one stvle of equipment may not be realized immediately, and several styles may need to be stocked In the latter case, the cost, though higher than the cost of stocking only one style, will be small compared to the potential cost of ac cidents resulbng from failure to use the equipment For the convenience of their employees, some companies maintain equipment stores on the plant premises (Fig 38-1) Policies differ with respect to who pays for personal protecbve equipment The cost of eve protection equipment that has prescrip tion-ground lenses, such as safety spectacles, is often shared by worker and employer For instance, a National Safety Council survey showed that 27 per cent of the companies supplying employees with prescnphon gog gles gave them free, and 60 per cent assumed part of the cost or made them available at below retail Most companies do not furnish safetv toe shoes free Many industrial firms maintain shoe stores for the convenience of employees and make the shoes available at cost In some instances, to encourage purchases, safety shoes are offered at below-cost prices In some areas, shoemobile service is avail- 1144

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Occupational Health Services Medical and surgical management in every case of industrial injury or disease should aim to restore the disabled worker to his former earning power and occupation as com pletely as possible and without unnecessary delay Concise, dependable medical re ports that are promptly submitted to those agencies entitled to them are a part of this obligation In the same way, equitable ad ministration of workmen's compensation rests on medical testimony which adheres closely to reasonable scientific deductions regarding the injury or its possible conse quences The industrial physician is responsible for maintenance and completeness of medical records Records and reports are a necessary part of an occupational medical program Comprehensive records must be kept and re ports rendered m order that management be guided in their continuing responsibility for health and safety, and the employees kept in formed of the degree of success of the safety program afforded by their cooperation Rec ords and reports are necessary to direct and evaluate preventive medical and safety engi neering techniques They are necessary to chart progress in the reduction of accidents The physician is also responsible for prop erly instructing nurses and other paramedical personnel (such as first-aiders) and directing their activities Their duties, therefore, should be described in clear, concisely writ ten directives, a copy of which should be posted in the medical department There must be no delegation of services requiring expert medical attention The industrial physician, nurse, and safety director should concur with management to plan for emergency handling of large num bers of seriously injured employees in the event of disaster, such as explosion, fire, or other catastrophe These plans should be coordinated with community plans for such events See "Planning for Emergencies," Chapter 37 Procedures should include selecting, train ing, and supervising auxiliary personnel, and should provide for 1 Selecting and training auxiliary nursing personnel 2 Selecting and training first aid workers 3 Transporting and canng for the injured 4 Transferring seriously injured to hospitals (where operating rooms and blood trans fusions are available, donors could be arranged for) 5 Coordinating these plans with the safety department, guards, police, road patrols, fire departments, and other interested community groups Duties of the occupational health nurse Occupational health nursing is a special ized branch of the nursing profession The position requires a registered professional nurse, who is licensed in the state where employed In addition, it is desirable that the occupational health nurse have some knowledge of workmen's compensation laws, insurance, health and safety laws, occupa tional diseases, sanitation, first aid, and rec ord keeping The occupational health nurse contributes the most when she works with the company physician who provides her with written di rectives that have been discussed between them, so they are mutually agreed upon and understood Working with the physician, the occupa tional health nurse can provide a variety of nursing services, such as initial care for in juries or illnesses, counseling, health educa tion, consultation about sanitary standards, and referral to community health agencies She also can participate in programs to eval uate employee health, such as health exam inations, or to prevent disease, such as im munizations When the physician is only located at the plant part time, the nurse is responsible to him on professional matters, and to a mem ber of management on administrative matters In this case, the nurse works with the safety director m planning and conducting accident prevention programs The occupational health nurse must main tain a confidential professional relationship with the employees m conformity with legal and ethical codes She may not divulge in formation contained in individual employee health records unless the employee gives his signed permission, the medical files are only accessible to medical personnel It must be clear that establishment of medi cal diagnosis and definition of treatment are 1226

1313 Substance *' Heptane (n-heptane) Hexachloroethane--Skin * Hexachloronaphthalene-Skin Hexane (n*hexane) 2-Hexanone Hexone sec-Hexyl acetate Hydrazine--Skin Hydrogen bromide C Hydrogen chloride Hydrogen cyanide --Skin Hydrogen ftuonde Hydrogen peroxide 90% Hydrogen selemde Hydrogen sulfide Hydroqumone C Iodine Iron oxide fume Isomyl acetate Isoamyi alcohol Isobutyl acetate * Isobutyl alcohol Isophorone Isopropyl acetate Isopropyl alcohol Isopropylamine Isopropylether isopropyl giycidy!

Elements of Industrial Toxicology the eyes, nose, throat, and lungs Dichloromethane --see Methylene chlo ride.

or into the pores of a concrete floor, the con tamination may become so great as to necessi tate replacement or sealing of the floor before the plant or laboratory can be safely used again Although it cannot be removed, mer cury can be sealed into such floors by cover ing them completely with an asphalt mastic, preferably after the vapor pressure of the mercury has been reduced by flooding the whole area with a lime sulfur spray To prevent such inconvenience, metallic mercury should be handled over impervious tables or containers with the surfaces de pressed and arranged to drain to a central point Spilled mercury can then be collected and returned to stock A number of volatile mercury compounds are used in seed disinfection Examples are ethyl mercury chloride and phosphate and the corresponding phenyl mercury com pounds These materials are highly toxic When used without adequate enclosure and dust control, they can rapidly produce severe mercurial intoxication These seed-treating compounds are also strong primary skin irri tants and will cause itching, burning, and blistering on direct contact Such irritations heal slowly The type of mercurv intoxication common to industry is characterized by a tremor of the hands, irritation of the mucous membranes of the mouth, excessive flow of saliva, and changes in the personality Poisoning by one of the volatile compounds may be more rapid so that personality changes are not so likely to be seen Inhalation of mercury vapor, usually in very high concentrations, mav produce metal fume fever, which may disappear with no other apparent symptoms, or may be followed by a pneumonitis or other symptoms of mercunalism The ordinary toxic dust respirator does not protect against intoxication by metallic mer cury or by the volatile seed-treating com pounds, since they are in the form of vapor rather than dust A gas mask offers some pro tection, but if enclosure and local exhaust are not possible, the only effective protection is a supplied air respirator See Industrial Data Sheet 203 and Hygtemc Gutde Mesityl oxide is a high-boiling, unsaturated ketone which is thought to be somewhat more toxic than the ketones of lower molecular weights Metal hydrides (primary types) are com pounds of hydrogen and the alkali metals sodium, potassium, lithium, magnesium, cal cium, and strontium Information on the health hazards of metal hydrides is limited Since they react with water to form caustic hydroxides, they are irritating to the eves, skin, and mucous membranes They also re lease a large amount of heat on reaction with the moisture of the skin See Industrial Data Sheet 462 and Hygienic Gutde Methanol (methyl alcohol) poisoning is usually produced bv swallowing the liquid or inhaling high concentrations of vapor in an enclosed place such as a tank The signs of poisoning include headache, nausea, vomit ing, violent abdominal pains, aimless and erratic movements, dilated pupils, sometimes delinum, and such eye symptoms as pain, tenderness on pressure, and occasionally blindness Direct action of the liquid or the vapor on the skin and mucous membranes may pro duce an irritation and inflammation One of the peculiarities of methanol poi soning is its exceptionally severe action on the optic nerve About one-half of all the serious cases of methanol poisoning result in some impairment of vision, which is usually permanent and may vary from dimness or blind spots scattered through the visual field to total blindness See Industrial Data Sheet 407 and Hygienic Guide Methoxychlor (2,2-di [ p-methoxypheny1 ] 1,1,1-tnchloroethane) is a synthetic insecti cide which is closely related to DDT m its action It is, however, about '/ to `/io as toxic as DDT Consequently, the hazard from in halation of the dust or mist of sprays of this insecticide is remote Methoxychlor is not absorbed through the intact skin in significant amounts, and does not seem to have any effect on the central nervous system In animal experiments, con tinued feeding of diets containing methoxy chlor m toxic concentration leads to loss of weight in the animals by their voluntary re striction of food intake and also to fatty m- 1357

installation should be used In some instances (e g , where large pieces must be handled), a radiography room is not practical An area within the plant must be roped off and posted with warning signs or otherwise barricaded to prevent unauthorized personnel from entering the area Sometimes it has been found that segregating the opera tion with respect to time is the only solution to this problem, that is, to perform radiog raphy at night or other times when there are no other workmen m that part of the plant Others have solved the problem by fencing off an open area outside the buildings m such a manner that unauthorized persons cannot enter the high radiation zones Similar measures must be taken to restrict areas where radiography is performed in the field Radiation safety problems in field radi ography can be complicated by the curiosity of bystanders, the presence of other unin formed workers on the project and possible temporary misplacement of a "free" gamma source In such field applications as radiog raphing welds on pipelines, pressure tanks, refineries and other construction projects, there should be a thoroughly trained radia tion safety supervisor in charge of the work He is responsible for maintaining adequate precautionary measures to prevent unneces sary exposure of personnel Radiation warning signs should be posted and restrictive barriers erected to control traffic in the vicinity of an exposed source The warning sign should include (a) DangerRadiation, Keep Away (Do Not Loiter) and (b) the radiation symbol, Fig 44-15 Radiation safety rules should be explained to the workers and their cooperation enlisted m maintaining a safe standard of operation Where a project may be delayed by restricting the area to other workers, here again, con sideration should be given to making radiog raphs at odd hours when few or no other per sons are around The contractor should be made aware of the safe limits of radiation ex posure so that unreasonable production sched ules are not requested Generally speaking, the most important item with regard to field radiography is to make sure that the restricted site is always under surviellance by the per son in charge so that unauthorized workers, bystanders, or curiosity seekers do not enter An appropriate survey instrument should 3R FlC 44-15 --The American Standards Institute recommends this symbol for radiation warning signs Symbol should be reddish-purple, displayed against a yellow background and should be accom panied by the word "RADIATION" in yellow let ters on reddish-purple panel Radiation signs should be proportioned the same as "danger" signs and sized according to the area to be marked See ASI Standard N2 1 "Radiation Symbol " be immediately available at each field in stallation Radiation surveys of the radiog raphic setup for the purpose of establishing working times within the area should be a routine procedure m the field A survey gives the operator a quick means of determining dose rates around the site and determining where restrictive barriers should be placed Personnel monitoring, such as film badges, s also essential for those workers engaged m routine radiographic work Although misplacement ofradiation sources is not to be tolerated, it is possible for them to be accidentally dropped behind equipment and in locations where the capsule is not vis ible Small sources should therefore be tagged or labeled Where a source is mis placed, every effort should be made to re cover the source immediately without over exposure to personnel Without the use of a survey instrument, such as a geiger or scin tillation counter, it would be difficult, if not 1471

MetalStamping--Chairmati--Ahvma B, Auerhaan, Corp.