a. Absorption of Mercury by the Body

of the mercury taken in by this route being absorbed. A relatively minor amount is absorbed by

the skin or large droplets reaching the gastrointestinal track, perhaps 15%, although when

exposures by this route occur, the exposure level is likely to be high. Inorganic mercury is

transformed to some extent by microorganisms in the mouth and gut to short-chain alkyl(methyl

and ethyl) forms, which are readily absorbed. Further distribution of absorbed mercury is

facilitated by the blood.

Inorganic and organic mercury compounds have a strong affinity for thiol chemical groups.

Most proteins and all enzymes contain these groups so that mercury readily is bound to body

tissues. Most mercury compounds are potent enzyme inhibitors which affects membrane

permeability, which in turn affects nerve conduction and tissue respiration.

The biological half-life of mercury in the blood is approximately three days, following an

exposure but the mercury bound to body tissues clears much more slowly with a half-life of about

90 days. Thus the end of an exposure will have long lasting effects. The levels in tissue will not

fall below 10% of the peak level until somewhat more than four half-lives have passed.

The kidney plays a key roll in the absorption of mercury in the body. Kidney tissue contains

a thiol-rich protein called metallothionein. Exposure of the kidney to mercury and other toxic

metals causes production of this protein which binds the metals tightly, and retains it in the

kidney in a relatively harmless form. As long as the kidney is not overwhelmed by the influx of

the toxic metal, the excretion of mercury will eventually balance intake so that worsening of

adverse symptoms will be limited. However, acute levels can lead to renal failure.

Chronic mercury exposure can seriously affect fertility and the outcome of pregnancy.

Mercury passes readily through the placenta and the concentration in the cord blood is elevated

above the maternal blood. In men, organic forms of mercury can cause hypospermia, and a

reduction in libido and cause impotence in some men. For some men, there has been an increase

in the rate of spontaneous abortion in their partners.

b. Excretion of Mercury

Mercury is excreted by the body through the feces and urine, with a minute amount by the

respiration. The liver excretes some in bile, which is partially reabsorbed but is eventually

disposed of by the kidney. Some mercury passes directly by the body in the urine instead of

being bound by proteins. For a steady state exposure, the urine level reflects body burden of

mercury. Another indicator of mercury intake is the concentration of mercury in the hair. As the

hair grows the mercury levels can be measured along the length of the hair by such techniques

as neutron activation analysis.

c. Control Measures

Mercury is dense (specific gravity of just under 13.6 a t 4"C (39.2"F)) and has a high surface

tension and low viscosity. As a result, it tends to break up into small droplets when it is poured

or spilled. Anyone who has tried to pick up small droplets using a stiff piece of paper can attest

to the appropriateness of the alternate name “quicksilver.” As the droplets are disturbed as, for

example, when walked upon on the laboratory floor, they tend to break up into smaller and smaller

droplets, eventually becoming too small to see. In a laboratory where mercury has been in use

for an extended period of time, it is instructive to run a pen knife in the cracks in a tile floor or in

the seams where cabinets and bench tops fit together. Invariably, small droplets of mercury will

be found.

Although a thin film of oxide will form on the skin of mercury droplets, it is very fragile and

w ill break. Similarly, sprinkling flowers of sulfur on the location of a mercury spill has been

suggested as a control measure but the surface film which forms also apparently is also very

fragile and will allow the mercury underneath the film to be readily exposed.



©2000 CRC Press LLC



d. Exposure Reduction

One of the simplest control measures is to reduce the amount of mercury used in instrumentation and equipment. Mercury thermometers can be replaced with alternatives. Vacuum

gauges can be changed.

Mercury thermometers which used to be used almost exclusively in

hospitals, and which used to be a major source of spilled mercury, have been replaced by

electronic digital devices which have the further advantages of being quick and less intrusive.

At one time, the number of broken medical mercury thermometers was estimated at two per bed

per year. One of the major sources of dumped mercury in the United States used to be from

disposal of dry cell batteries, accounting for 86% of the total. One should look for statements

on batteries declaring them to be mercury-free or nearly so before making a purchase.

Wherever possible, work with mercury should be done in a fume hood, preferably one that

has a depressed surface, so that a lip will aid in preventing mercury spills from reaching the floor,

and with a seamless interior, as recommended for radiological work and work with perchloric acid.

As noted earlier, heating mercury causes it to emit fumes at concentration levels two to three

orders of magnitude above the PELs. Heating of mercury should never be done on the open

bench.

The general restrictions on eating, drinking, and smoking in the laboratory should be strictly

enforced in laboratories where mercury compounds are commonly used. Depending upon the

level of use and the availability of fume hoods, the use of personal protective equipment is

recommended in addition to the use of goggles and laboratory aprons. Respiratory protection,

consisting of half-face respirators fitted with a cartridge which will absorb mercury, should be

considered if there is any potential for mercury exposure. A number of mercury compounds are

absorbed through the skin and are strong allergens. The skin in such cases should be protected

with gloves covering the forearms as well as the hands.

Vinyl tile is a commonly used material for the floors in a laboratory because it is “easy” to

maintain and inexpensive to install. Ease of maintenance is not the case for a tile floor in a

laboratory using mercury, because of the propensity of the extremely small (20 microns or less)

mercury droplets to collect in the cracks. A seamless vinyl or poured epoxy floor should be used

instead, with the joints of the floor with the wall being curved or “coved.” Similarly, the bench

top should be curved where it joins the back panel. Existing tile floors, especially the smaller 9

inch x 9 inch size, frequently represent an additional maintenance problem since a large proportion

contain asbestos, as may the mastic holding them to the floor. When these tiles need replacing,

the work must be done in conformance with EPA and OSHA asbestos standards and can be very

costly. One procedure to be avoided at all costs is to grind up the old tile. This can distribute

asbestos fibers so widely that the already expensive asbestos removal can be made prohibitively

so.

e.



Monitoring

The fumes from mercury provide no direct sensory evidence that they are present. Where

use is substantial, monitoring measures should be readily available. The least expensive means

to detect mercury levels is a detector tube in which a given volume of air is pulled through a glass

tube containing a material that undergoes a color change when mercury comes into contact with

the material. Normally the air is drawn through by means of a hand-operated pump. This method

provides a reasonable accuracy but any finding within approximately 25% of the PEL should be

considered to be sufficient warning of a possible overexposure of personnel working in the area.

Each measurement requires a new tube. A popular instrument used to provide a direct reading

of mercury concentrations in the air is a hand-held atomic absorption spectrometer in which air

contaminated with mercury is drawn through the instrument and the degree of interference with

ultraviolet light of the wavelength corresponding to a characteristic line of the mercury spectrum

is translated into a numerical reading of the concentration of mercury in the air. The calibration

of these instruments must be carefully maint ained. Another instrument which provides an



©2000 CRC Press LLC



accurate, rapid reading of the level of mercury in the air depends upon the property of mercury

to amalgamate with a thin gold film. This latter type of instrument is probably the most accurate

and reliable but is also the most expensive. Unless the work with mercury compounds is quite

heavy, the laboratory may be unable to afford either of the last two types of monitoring devices.

In such a case, the safety department should be provided with an instrument to be used at all

locations within an organization.

f. Spill Control Measures

Large globules of mercury can be cleaned up mechanically by carefully brushing them onto

a dustpan or a stiff piece of paper. Another simple device is the use of a small mechanical handheld pump to suck the globules into a small container. This is a tedious procedure limited to small

spills and, of course, to droplets big enough to be seen. Bulk mercury recovered by these

procedures can be recovered and purified for reuse.

Mercury spill kits available commercially usually include a small pump, sponges impregnated

with a material to absorb mercury and which can be used to wipe up the area of a small spill, and

a quantity of an absorbent powder that reacts with mercury to form a harmless amalgam. The latter

can be spread on cracks and seams in the floor and furniture and is effective in collecting mercury

from otherwise inaccessible places. After leaving the material on the floor or contaminated

surfaces for several hours in order to allow the amalgam to form, the powder can be swept or

brushed up and the waste material disposed of as a hazardous waste.

Ordinary vacuum cleaners MUST NOT be used to clean up a mercury spill. An ordinary

vacuum filter bag will not stop an appreciable fraction of small particles in the region of several

microns or less and, more importantly, the mercury globules pulled into the bag will be broken

up into even finer droplets and spewed out of the vacuum's exhaust into the air, substantially

increasing the surface area of mercury exposed to the air and greatly enhancing the rate at which

mercury vapor will be generated. There are commercial vacuum cleaners which are specifically

designed to pick up mercury, however. One such unit, sold by Nilfisk of America, which also

makes specialized units for other toxic materials, first draws the mercury into a centrifugal

separator and collects the bulk of the material into an airtight plastic bottle. The contaminated

air is then passed into a collection bag which collects bulk solid waste and then through an

activated charcoal filter. Additional filters (some optional) follow the charcoal filter collector. This

unit can be used to clean up virtually any spill alone but can be used with other control measures

to ensure a complet e clean up of the spilled material. The hose in the Nilfisk unit vacuum cleaner

has an especially smooth surface to prevent mercury particles from adhering to the inside of the

hose. As with most specialized units, the vacuum cleaner is not inexpensive. In some instances,

a special purpose mercury vacuum cleaner is virtually indispensable for use on a spill on a

porous, rough material such as carpeting. The use of carpeting as a laboratory floor covering

is very rare but, in at least one instance where this was done, a large area of the carpet was

thoroughly contaminated by an extensive mercury spill.

g. Ventilation

The ventilation system in a laboratory using mercury or mercury compounds should conform

to the general recommendation that wet chemistry laboratories involving any hazardous material

be provided with 100% fresh air instead of having a portion of the air recirculated. Local

ventilation systems, such as the exhausts of mechanical pumps servicing mercury diffusion

pumps, should be collected with a local exhaust system and discharged into the fume hood

exhaust system in the room or to a separate exhaust duct provided to service such units. The

mercury vapor is much heavier than air so it is important that the room exhausts be placed near

the floor or at the back of the workbench to collect as much of the vapors as possible.



©2000 CRC Press LLC



h. Medical Surveillance

It is recommended, as a minimum, that permanent employees working with mercury or mercury

compounds be provided with periodic physical examinations with a test protocol selected

specifically for mercury poisoning. Women who may be pregnant should be especially careful

and encouraged to participate in the medical surveillance program if they cannot avoid exposure

entirely.



REFERENCES

1.

2.



Vostal . J.J. and Clarkham, T.W., Mercury as an environmental hazard,. J. Occupational Medicine, 15,

649, 1973.

Armour, M.A., Browne, L.M., and Weir, G.L., Hazardous Chemicals Information and Disposal Guide,

2nd ed., University of Alberta, Edmonton, Canada, 1984.



INTERNET REFERENCES

1.

2.



http://www.mercury.safety.co.uk/hlthinfo.htm - Mercury Toxicity and how it affects our health, Mercury

Safety Products, Ltd., 1997.

http://www.chem.ucla.edu/Safety/newsletterl.html - Mercury cleanup and disposal .



9. Hydrofluoric Acid

Anhydrous hydrofluoric acid (HF) (CAS 7664-39-3) is a clear, colorless liquid. Because it boils

at 19.5"C (67.1"F) and has a high vapor pressure, it must be kept in pressure containers. It is

miscible in water, and lower concentration aqueous solutions are available commercially. It is an

extremely dangerous material and all forms, including vapors and solutions, can cause severe,

slow-healing burns to tissue. At concentrations of less than 50%, the burns may not be felt

immediately and at 20% the effects may not be noticed for several hours. At higher

concentrations, the burning sensation will become noticeable much more quickly, in a matter of

minutes or less. Fluoride ions readily penetrate skin and tissue and, in extreme cases, may result

in necrosis of the subcutaneous tissue which eventually may become gangrenous. If the

penetration is sufficiently deep, decalcification of the bones may result. The current OSHA PEL

8-hour time weighted average to HF is set at 3 ppm (2.5 mg/M 3), which also is the ceiling TLV

currently recommended by the ACGIH. Chronic exposure to even lower levels may irritate the

respiratory system and cause problems to the bones. Even brief exposures to high levels of the

vapors may cause severe damage to the respiratory system, although the sharp, irritating odor

of the acid will usually provide a warning to assist in avoiding inhalation in normal use. Contact

with the eyes could result in blindness. If eye exposure occurs, it is urgent to flush the eyes as

quickly as possible. It is especially recommended that every laboratory using hydrofluoric acid

have both an eyewash station and deluge shower within the laboratory. Dilute solutions and

vapors may be absorbed by clothing and held in contact with the skin, which will probably not

result in an immediate sensation of pain as a warning but eventually may lead to skin ulcers

which, again, may take some time to heal. A generalization might be made here about absorbent

clothing. In many instances, as in this case, absorbent clothing which can retain toxic materials

and maintain them in close contact with the skin may be worse than no protection at all, changing

the exposure from a transient phenomena to a persistent one. This is not always a problem, but

it should be kept in mind as a possibility when choosing protective apparel. All work with

hydrofluoric acid should be done in a fume hood.



©2000 CRC Press LLC



Hydrofluoric acid attacks glass, concrete, and many metals (especially cast iron). It also

attacks carbonaceous natural materials such as woody materials, animal products such as leather,

and other natural materials used in the laboratory such as rubber. Reactions with carbonates, and

sulfites and cyanide will produce asphyxiants or toxic gases. Lead, platinum, wax, polyethylene,

polypropylene, polymethylpentane, and Teflon will resist the corrosive action of the acid. In

contact with metals with which it will react, hydrogen gas is liberated and hence the danger exists

of a spark or flame resulting in an explosion in areas where this may occur.

a. Treatment to exposure

Successful treatment of severe exposures is dependent on rapid reactions by those

responding to the incident and by the affected person(s). In the following sections, reference

is made to various medications specific to the treatment of hydrofluoric acid exposure. It is

unlikely that the typical rescue squad called to the scene will have these medications so they

should be part of the first aid supplies maintained in the immediate area where exposures may

occur. Have someone call for emergency medical assistance as soon as possible and direct them

to arrange treatment with a physician or trauma center familiar with chemical burns. In all types

of exposure, the first action recommended is prolonged flushing with copious amounts of water

so an eyewash station, a shower and a source of potable water should be immediately available.

For an eye exposure, the eye should be flushed for 30 minutes, with the eyelids being kept

out of contact with the surface of the eye. For a skin exposure, any clothing in contact with the

affected area should be removed, with care, and the area flushed with running water for at least

20 minutes. If the affected area is large, do this in a safety shower or if restricted to a small area,

with a hose or a steady stream of water from another source.

A recommended first aid treatment for an eye exposure, while obtaining medical treatment,

is to apply one or two drops of 0.5% Pontocaine Hydrochloride solution. Afterwards, it has been

recommended that the eyes should be washed with a 1% calcium glutonate in normal saline

solution for 5 to 10 minutes. Subsequently, for the next two to three days, the eyes should

continue to be treated with this solution every two to three hours.

One suggested treatment for a skin exposure is to immerse the burned area, after thorough

washing, in a solution of 0.2% iced aqueous Hyamine 1622 * or 0.13% iced aqueous Zephiran

Chloride. If the area cannot be immersed conveniently, then towels soaked with these solutions

should be applied. The compresses should be changed every few minutes.

Another first aid treatment for surface burns from hydrofluoric acid is to rub the affected area

with a 2.5 % gel of calcium glutonate after a brief one minute washing. This can be continued

for 3 to 4 days and done 4 to 5 times daily. For burns of areas greater than 50 cm2, about 10 in2,

the patient should be hospitalized. As the area of the burn increases, the likelihood of inhalation

becomes greater and the victims pulmonary function should be carefully evaluated by the

attending physician.

For deep burns by greater than 20% solutions of HF, treatment by subcutaneous injections

of a 5% solution of calcium glutonate (prepared by diluting 10% ampules of the material) is

recommended. The injection should be limited to no more than 0.5 cc per square centimeter. One

authority does not recommend that this be done on the digits of the hand, or should be done

very carefully for all areas of the hands, feet and face. The same authority also states that

concentrations greater than 5% tends to produce severe irritation and can lead to the formation

of keloids and scarring.

If the exposure is inhalation of HF vapors, the victim should be provided with 100% oxygen

as soon as possible, followed quickly by inhalation of a 2.5 to 3% solution of calcium glutonate

using a nebulizer. The attending physician should watch for signs of edema of the upper airway



*



Hyamine is a trade name for tetracaine benzethonium chloride, Merck index Monograph 1078.



©2000 CRC Press LLC



and the airway maintained clear of obstruction.

Ingestion is less likely but if it occurs, severe burns can result which may be fatal. Call for

medical assistance immediately but, while waiting, the only first aid treatment recommended is

having the victim drink large quantities of water.



REFERENCES

1. Proctor, N.H. and Hughes, J.P., Chemical Hazards of the Workplace, J.B. Lippincott., Philadelphia,

1978, 290.

2.



Knight, A.L., Occupational Medicine: Principles and Practical Applications, Zenz, C. (Ed.), Year Book

Medical Publishers, Chicago, 1975, 649.



3.



Wetherhold, J.M. and Shepherd, E.P., Treatment of hydrofluoric acid burns, J. Occup. Med, 7, 193,

1965.



4.



Reinhardt, C.F., Hume, W.G., and Linch, A.L. et al., Hydrofluoric acid burn treatment, Am. Med. Hyg.

Assoc.J., 27, 166, 1966.



5.



Gosselin, R.D., Hodge, H.C., Smith, R.P. et al.., Clinical Toxicology of Commercial Products: Acute

Poisoning, 4th ed., Williams & Wilkins., Baltimore, 1976, 159.



6.



Browne, T.D., The treatment of hydrofluoric acid burns, J. Occup. Med, 24, 80, 1974.



7.



Tepperman, P.R., Fatality due to acute systemic fluoride poisoning following a hydrofl uoric acid skin burn,

J. Occup. Med, 22, 691, 1980.



8.



Abukurah, A.R., Moser A.M., Baird, C.L. et al., Acute sodium fluoride poisoning, JAMA, 222, 816,

1972.



9.



Thevino, M.A., Herrmann, G.H., and Sproul, W.L., Treatment of severe hydrofluoric acid exposures,

J. Occup. Med., 25(12), 861, 1983.



INTERNET REFERENCES

1. http://www.camd.lsuedu/msds/h/hydrofluoric_acid.htm

2.



http://www.qrc.com/hhmi/science/labsafe/lcss/lcss51.htm



3.



http://www.filemedia.com/hf/



4.



http://www.cdc.gov/niosh/npg/npgd0334.html



10. Hydrogen Cyanide

Hydrogen cyanide (HCN) (CAS 74-90-8), also called hydrocyanic acid or prussic acid, is an

extremely dangerous chemical that is toxic by ingestion, inhalation, or by absorption through

the skin. The current OSHA 8-hour PEL to the vapors from this chemical is 10 ppm, as is the

current ACGIH ceiling limit (with a cautionary note that skin absorption could be a contributory

hazard). The NIOSH recommended limit is 4.7 ppm. The material has a characteristic odor of bitter

almonds, but the odor is not usually considered to be sufficiently strong to be an adequate

warning of the presence of the vapors at or above the PEL. A substantial number of persons,

perhaps as many as 60%, cannot detect this odor. Not only is HCN toxic, it has a very low flash

point, -17.8"C (0"F), a lower explosion limit of 6%, and an upper explosion limit of 41%, so that

it also represents a serious fire and explosion hazards. It has a boiling point of 26"C (79"F), so

that it is normally contained in cylinders in the laboratory. Heating of the liquid material in a

pressure-tight vessel to temperatures above 115"C (239"F) can lead to a violent, heat-generating

reaction. The material is usually stabilized with the addition of a small amount (0.1%) of acid,

usually phosphoric acid, although sulfuric acid is sometimes used. Samples stored more than

90 days may become unstable.



©2000 CRC Press LLC



Hydrogen cyanide can polymerize explosively when amines, hydroxides, acetaldehyde, or

metal cyanides are added to the liquid material, and it also may do so above 184"C (363"F).

Although there will be variations among individuals, a concentration of 270 ppm in air is

usually considered fatal to humans. A few breaths above this level may cause nearly

instantaneous collapse and respiratory failure. Exposures at lesser levels may be tolerated for

varying periods, e.g., 18 to 36 ppm may be tolerated for several hours before the onset of

symptoms. Initial symptoms of exposure to HCN include headache, vertigo, confusion, weakness,

or fatigue. Nausea and vomiting may occur. The respiratory rate usually increases initially and

then decreases until eventually it becomes slow and labored, finally ceasing. The symptoms

reflect the mechanism by which the toxic action occurs. The chemical acts to inhibit the transfer

of oxygen from the blood to tissue cells by combining with the enzymes associated with cellular

respiration. If the cyanide can be removed, the transfer of oxidation will resume. On average,

absorption of 50 to 100 mg of HCN, directly by ingestion or through the skin as well as by

inhalation can be fatal.

Treatment of a person poisoned by HCN is based on the introduction of methemoglobin into

the bloodstream to interact with the cyanide ions to form cyanmethemoglobin. In any area where

HCN is being used, a special emergency kit should be provided, containing an ample supply of

ampules of amyl nitrite, a solution of 1% sodium thiosulfate solution, and an oxygen cylinder

accompanied by a face piece and tubing to permit administering the oxygen. This kit should be

labeled FOR HCN EMERGENCIES ONLY. For this kit to be useful, several individuals in the

area should be trained in how to use it effectively. Sodium nitrite might also be kept in the kit if

there is someone available qualified to administer drugs intravenously introduction of sodium

nitrate directly into the bloodstream has been suggested as a means to increase the rate of

conversion of cyanide to the thiocyanate, which is less toxic. Treatment should begin as soon

as possible after an acute exposure and after recognition of the symptoms in less intense

exposures. If the exposure has been due to contamination in the air in the area, the patient should

be removed from the area (if the source of vapor is from a cylinder, the valve on the cylinder

should be closed). Any contaminated clothes should be removed and the skin flooded with water.

If the patient is not breathing, resuscitation should be begun. As soon as the patient is

breathing, an open amyl nitrite ampule should be held under the patient's nose for 15 seconds

per minute, with oxygen being administered during the remaining 45 seconds. Medical aid should

be called for immediately. If there is a person available qualified to administer drugs intravenously,

injection of sodium nitrite while administering amyl nitrite should prove beneficial. Subsequent

intravenous injection of sodium thiosulfate also has been suggested as an ameliorative action.

Rescue squad teams usually have at least one member qualified to administer drugs while under

the direction (by radio) of an emergency room physician. If the patient has swallowed HCN, the

recommended treatment is to get the patient to swallow one pint of the sodium thiosulfate

solution, followed by soapy water or mustard water to induce vomiting. Vomiting should not be

induced in an unconscious patient. Application of amyl nitrite may restore consciousness.

All work with HCN must be done in a fume hood, operating with a face velocity of at least

100 fpm and with the apparatus set well back from the face of the hood to ensure that all vapors

will be captured and discharged by the exhaust system. The hood should comply in every respect

to recommended good practices for the location, design, and operations of hoods in Chapter 3.

The hood should have its own individual duct to the roof. If the work is a continuing program,

the exhaust duct should be labeled: DANGER, DO NOT SERVICE OR WORK IN THE VICINITY

WHILE UNIT IS OPERATING.

Protective gloves and chemical splash goggles should be worn while working with HCN. No

one should work alone with this material. The laboratory entrance(s) should be posted with a

warning sign: DANGER, HCN, AUTHORIZED PERSONNEL ONLY. As noted above, care needs

to be taken to be sure that persons outside the area, such as workers on the roof, are not



©2000 CRC Press LLC



inadvertently exposed. All work with HCN should be done in trays or other shallow containers

of sufficient capacity to retain any spill from the apparatus.

Cleaning up of spills represents a serious problem with a chemical as dangerous as HCN, so

extra care should be taken to avoid accidents with the material. If a spill occurs outside a hood,

the laboratory should be evacuated as quickly as possilble. All ignition sources and valves to

cylinders of HCN should be turned off. If any individuals are splashed with the compound in an

accident, they should immediately remove their contaminated clothes and step under a nearby

deluge shower, preferably located in a space outside the laboratory in which the accident

occurred. The occupants of the latter space should be warned of the accident and encouraged

to evacuate as well. If the spill is substantial, the evacuation of either all the contiguous spaces

or the entire building might be considered. The evacuation of additional spaces is especially

important in facilities in which the reentry of fumes exhausted from the building is known to be

a problem. Medical observation and care for any exposed persons should be obtained as soon

as possible. It would be desirable to have sufficient self-contained escape-type breathing devices

on hand to equip every occupant of the laboratory. Unless laboratory personnel have received

specific training in handling hazard material incidents, the nearest hazardous material emergency

response center should be called for assistance for a substantial spill.

Hydrogen cyanide is categorized as a chemical which is immediately dangerous to life and

health (IDLH). As such, clean up of spills should be handled very carefully. Individuals

performing the clean up should wear a self-contained, positive pressure breathing apparatus,

equipped with a full face piece, rubber or neoprene gloves, and chemically protective outer-wear.

A type C supplied air respirator unit operated at a positive pressure can be used as well, but a

self-contained unit should be available as a backup. Anyone asked to wear this equipment must

have received prior training in the proper use of the equipment. The material can be cleaned up

using absorbent pillows or other absorbent materials. Waste should be placed in double heavyduty plastic bags, which are then tightly closed by twisting the top, folding the top over and

wrapping it securely with duct tape. The sealed plastic bags should then be placed in heavy

plastic containers or steel drums which can be tightly sealed. Waste material should not be placed

in fume hoods to evaporate or be disposed of in drains. In the latter case, the possibility of fumes

collecting in sections of the drain piping and reentering a building thorough a dry sink trap is

too great. The waste should not go to a normal landfill. Incineration is the preferred means of

disposal.

A leaking cylinder which cannot be readily repaired should be taken to a remote location

where the gas in the cylinder can be released safely. Cylinders which are damaged but not leaking

should be returned to the vendor for disposal wherever possible. Disposal of gas cylinders by

commercial hazardous waste firms can be very expensive.



REFERENCES

1.



Occupational Health Guidelines for Chemical Hazards, Mackison, F.W, Stricoff, R.S., and Partridge, Jr.,

L.J., (Eds.), U.S. Departmentof Health and Human Services and U.S. Department of Labor. DHHS (NIOSH)



2.



Prudent Practices in the Laboratory, Handling and Disposal of Chemicals, National Academy Press,

Washington, D.C., 1995.

Chen, K.K. and Rose, C.L., Nitrite and thiosulfate therapy in cyanide poisoning, JAMA, 149, 113, 1952.

Hirsch, E.G., Cyanide poisoning, Arch. Environ. Health, 8, 622, 1964.



Pub. No. 81-123, 1981.



3.

4.



©2000 CRC Press LLC



INTERNET REFERENCES

1. http://www.cdc.gov/niosh/npg/npgd0333.html

2.

3.



http://www.qrc.com/hhmi/science/labsafe/lcss/lcss50.htm

http://www.state.nj.us/health/eoh/rtkweb/rtkhsfs.htm



11. Fluorine Gas

Fluorine (CAS no. 7782-41-4) is an extremely reactive gas which reacts violently with a wide

variety of materials, a representative sample of which are most oxidizable substances, most

organic matter, silicon-containing compounds, metals, halogens, halogen acids, carbon, natural

gas, water, polyethylene, acetylides, carbides, and liquid air. Many of these reactions will initiate

at very low temperatures. Because it will react with so many materials, extreme care must be taken

when working with fluorine. The work area should be very well ventilated and free of combustible

materials which would act as fuel in the event of a fire. A written hazard analysis should be

prepared for the research program prior to beginning work and an emergency contingency plan

developed as a part of the laboratory industrial hygiene plan required by the OSHA laboratory

standard. Written standard operating procedures are required, and employees fully trained in the

nature of the risks and protective measures necessary to avoid injury.

The OSHA PEL is 0.1 ppm or 0.2 mg/M 3. However, the 1993-94 ACGIH TWA levels are 10

times higher with short-term exposure limits (STEL) another factor of 2 higher. An exposure to

25 ppm for 15 minutes has caused severe eye symptoms. The LC 50 (50% lethal concentration) for

a 1-hour exposure for rats and mice is 185 and 150 ppm, respectively. It is highly irritating to

tissue.

Fluorine will react with brass, iron, aluminum, and copper to form a protective metallic fluoride

film. Circulating a dilute mixture of fluorine gas and inert gases through a system of these metals

will passivate the surfaces and render them safe to use, provided the film remains intact. However,

it is recommended that an inert gas be circulated through any fluorine system before the fluorine

is introduced.

All systems containing fluorine should be checked frequently for leaks. Filter paper moistened

with potassium iodide can be used to perform the tests. The paper will change color when any

escaping gas comes in contact with it.

Work with systems using fluorine should always be done within a fume hood. The research

worker should be protected by an explosive shield. The worker should also wear protective

goggles and a face mask. Unless the cylinder valve is operated through a remote control device,

the user should wear sturdy gloves with extended cuffs to protect his hands and arms while

manipulating the valve. A protective apron should be worn as well. However, all of these may

give only limited protection in the event of an accident since fluorine may react with many

common items of personnel protective gear.

Self-contained escape breathing apparatus should be available for all occupants of a laboratory in which fluorine is in active use. In the event of an accident, immediate evacuation of

the area should take place, being sure to close doors as personnel leave to isolate the problem

as much as possible. Evacuation of nearby areas should be considered or, depending upon the

scale of the accident, perhaps the entire building, especially as noted elsewhere, if there are

known problems with exhausted materials reentering the building. No remedial measures should

be attempted under most circumstances; the incident should be allowed to proceed until the

fluorine supply is exhausted. Firefighting efforts should be aimed at preventing a fire from

spreading. Applying water directly to the leak could intensify the fire. Obviously, it would be

desirable to use smaller cy linders, if practicable, for the research program to reduce the scale of

any incident.

Cylinders with valves that cannot be dislodged without application of sufficient force to

damage the valve or the connection to the cylinder should be returned to the vendor for repair

rather than take a chance on a massive rupture and release of the contents of the cylinder.



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Ordinary maintenance personnel should never be asked to attempt to free the valve. Although

the consequences here would be exacerbated by the extremely hazardous properties of the

contents of the cylinders, the same recommendation would apply to virtually any cylinder

containing a substantial volume of gas under high pressure. There are firms that specialize in

handling dangerous situations such as peroxides, explosives, highly reactive materials, and

damaged cylinders.



REFERENCES

1.



Occupational Health Guidelines for Chemical Hazards, Mackison, F.W., Stricoff, R.S., and Partridge, L.J.,Jr.,

(Eds.), U.S. Department of Health and Human Services and U.S. Department of Labor, DHHS (NIOSH)

Pub. No. 81-123, 1981.



2.

3.



Hazardous Chemical Data, NFPA-49, National Fire Protection Association, Quincy, MA.

Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices,

American Conference of Governmental Industrial Hygienists, Cincinnati, OH, 1993-1994.



INTERNET REFERENCE

1. http://www.cdc.gov/niosh/npg/npgd0289.html

12. General Safety for Hazardous Gas Research

The previous section was devoted to fluorine as an example of an exceptionally hazardous

gas. However, many others commonly used in the laboratory pose comparable risks, some

because of their own toxicity or that of gases or vapors evolved as a consequence of their

decomposition, others because of their flammable or explosive properties or due to reactions with

other chemicals, or a combination of all of these characteristics. Even relatively innocuous gases

such as nitrogen, carbon dioxide, argon, helium, and krypton can be a simple asphyxiant if they

displace sufficient air, leaving the oxygen content substantially below the normal percentage.

If the content of these inert gases approaches one third or higher, symp toms of oxygen

deprivation begin to occur, and at concentrations of around 75%, persons will survive for only

a brief period. Any gas under high pressure in a cylinder poses a problem if the cylinder is

mishandled so as to rupture the containment of the gas. In such a case the cylinder can represent

an uncontrolled missile with deadly consequences for anyone in the vicinity. The ability of

escaping gas to move readily throughout a volume greatly enhances the likelihood that a

flammable gas will encounter a source of ignition. This problem is shared by the vapors of many

volatile liquids. Many gases are heavier than air and may collect in depressions or areas with little

air movement, representing a danger to unsuspecting persons. Gases often do not have a

distinctive odor or are not sufficiently irritating to warn of their presence, and some that do, such

as hydrogen sulfide, act to desensitize the sense of smell at levels which would be dangerous.

Cylinders connected to systems in the laboratory must always be strapped firmly to a support

to ensure that they do not fall over. Not only is there a risk of breaking the connection on the

cylinder side of the regulator valve, with the concomitant risk of the cylinder becoming a missile,

but the connection to the system also may be broken so that gas will escape from the low

pressure side of the regulator. If the amount of gas to be stored in the laboratory is substantial,

it may be preferable to pipe the gas in from a remote outside storage area with control valves

located both outside and within the laboratory.

Where the explosion risk is substantial, the facility may need to be designed with explosion

venting so that the force of any explosion and the resulting flying debris can be released in a

relatively safe direction, minimizing the risk to the occupants. Systems for smaller-scale operations



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should be placed within a hood, perhaps one specially designed to provide partial protection

against explosions. Explosion shields are available to aid in protecting the research worker.

Wherever the possibility of an explosion exists, laboratory personnel should wear impactresistant goggles, possibly supplemented by a face mask to protect the lower part of the face and

throat. Gauntlets should be worn if there is risk to the hands and forearms while conducting

experimental evolutions.

Not all work with high pressures involves gas cylinders. Reaction bombs are commercially

available which operate at pressures up to 2000 psi (13.8 MPa) and temperatures up to 350 "C

(662"F). An error on the part of the research worker could permit these design parameters to be

exceeded, and although these units are designed with a substantial safety factor, the failure of

one of them could lead to disastrous consequences. Not only is there the immediate danger of

injury due to flying components of the system, there is the risk of reactions involving reagents

from broken bottles. These secondary events could escalate the consequences far beyond the

original scope of the incident. Any device in which the potential for a high-pressure accident

exists should be set up in a hood to provide some explosion protection, and explosion barriers

should be used to provide additional protection to the occupants of the room. Personnel working

in this type of research should be especially careful to not work alone. They should wear goggles,

a face mask, and sturdy gloves to protect their hands and forearms.

Systems involving toxic gases should be adequately ventilated. If possible, the systems

should be set up totally within a fume hood. Large walk-in hoods often are used for this purpose.

All systems should be carefully leak-tested prior to introduction of toxic materials into the system,

periodically thereafter, and after any maintenance or modifications to the system which could

affect its integrity.

Many gases are potentially so dangerous that access to the laboratory should be limited to

essential personnel that are authorized to be present. When working with such materials, no one

should work alone. It may be desirable to have one of the persons somewhat removed from the

immediate area of operations, but a second person should be within the working area. Entrances

to a high hazard gas research facility should be marked with a DANGER, SPECIFIC AGENT,

AUTHORIZED PERSONNEL ONLY or a comparable warning sign. Hood exhausts also should

bear a comparable warning legend. In some cases, automatic alarm sensors have been developed

to detect the presence of gas levels approaching dangerous levels. It is recommended that

warning trip points on these devices be set at no more than 50% of either the OSHA PEL or the

ACGIH TLV value, whichever is lower. If an automatic sensing device is available, circuitry can

be devised to activate a valve to cut off the gas supply as well as to provide a warning. The latter

is especially important if the operation is left unattended and no signal is transmitted to a manned

location, rendering an alarm ineffective. The growing application of programmed personal

computers, or laboratory computer workstations dedicated to experimental control has increased

the amount of sophisticated experimentation that can be automated.

In any laboratory involving the use of highly hazardous materials, an emergency plan is

required by OSHA to be developed in advance of initiation of any major project or any major

modification to an ongoing project based on a thorough hazard analysis. Because of the special

problems associated with gases, the emergency contingency plan should make provision for rapid

evacuation of the immediate laboratory using short-duration, self-contained breathing apparatus

and provision for initiation of evacuation from other areas of the facility. Provision of detailed

information to emergency response groups is now required under the Community Right-to-Know

law for many hazardous substances when the amount involved exceeds a prescribed threshold

amount. It is also recommended that employees involved in any research involving hazardous

materials participate in a medical surveillance program, consisting of a comprehensive prior

screening exam, acquisition of a serum sample for comparison with a sample following a possible

incident, and a complete medical history, so that baseline information on individuals will be

available to medical personnel called upon to treat personnel that may have been exposed, as



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