HEALTH AND SAFETY INFORMATION FOR WORK WITH CHEMICALS OF SPECIFIC HAZARD CLASS |
FLAMMABLE LIQUIDS |
General Information |
Flammable liquids are among the most common of the hazardous materials found in laboratories. They are usually highly volatile (have high vapor pressures at room temperature) and their vapors, mixed with air at the appropriate ratio, can ignite and burn. By definition, the lowest temperature at which they can form an ignitable vapor/air mixture (the flash point) is less then 37.8 oC (100oF) and for several common laboratory solvents (ether, acetone, toluene, acetaldehyde) the flash point is well below that. As with all solvents, their vapor pressure increases with temperature and, therefore, as temperatures increase they become more hazardous. |
For a fire to occur, three distinct conditions must exist simultaneously: |
1. the concentration of the vapor must be between the upper and lower flammable limits of the substance (the right fuel/air mix); |
2. an oxidizing atmosphere, usually air, must be available; and |
3. a source of ignition must be present. |
Removal of any of these three conditions will prevent the start of a fire. Flammable liquids may form flammable mixtures in either open or closed containers or spaces (such as refrigerators), when leaks or spills occur in the laboratory, and when heated. |
Control strategies for preventing ignition of flammable vapors include removing all sources of ignition or maintaining the concentration of flammable vapors below the lower flammability limit by using local exhaust ventilation such as a hood. The former strategy is more difficult because of the numerous ignition sources in laboratories. Ignition sources include: open flames, hot surfaces, operation of electrical equipment, and static electricity. |
The concentrated vapors of flammable liquids are heavier than air and can travel away from a source a considerable distance (across laboratories, into hallways, down elevator shafts or stairways). If the vapors reach a source of ignition, a flame can result that may flash back to the source of the vapor. |
The danger of fire and explosion presented by flammable liquids can usually be eliminated or minimized by strict observance of safe handling, dispensing, and storing procedures. |
Special Handling Procedures |
While working with flammable liquids you should wear gloves, protective glasses, and long sleeved lab coats. Wear goggles if dispensing solvents or performing an operation which could result in a splash to the face. |
Large quantities of flammable liquids should be handled in a chemical fume hood or under some other type of local exhaust ventilation. Five gallon containers must be dispensed to smaller containers in a hood or under local exhaust ventilation. When dispensing flammable solvents into small storage containers, use metal or plastic containers or safety cans (avoid glass containers). |
Make sure that metal surfaces or containers through which flammable substances are flowing are properly grounded, discharging static electricity. Free flowing liquids generate static electricity which can produce a spark and ignite the solvent. |
Large quantities of flammable liquids must be handled in areas free of ignition sources (including spark emitting motors and equipment) using non-sparking tools. Remember that vapors are heavier than air and can travel to a distant source of ignition. |
Never heat flammable substances by using an open flame. Instead, use any of the following heat sources: steam baths, water baths, oil baths, heating mantles or hot air baths. |
Do not distill flammable substances under reduced pressure. |
Store flammable substances away from ignition sources. The preferred storage location is in flammable storage cabinets. If no flammable storage cabinet is available, store these substances in a cabinet under the hood or bench. Five gallon containers should only be stored in a flammable storage cabinet or under a hood. You can also keep the flammable liquids inside the hood for a short period of time. Storage in chemical fume hood is not preferred because it reduces hood performance by obstructing air flow. |
The volume of flammable liquids dispensed in small containers (not including safety cans) in the open areas of laboratories should not exceed 10 gallons in most laboratories. Never store glass containers of flammable liquids on the floor. |
Oxidizing and corrosive materials should not be stored in close proximity to flammable liquids. |
Flammable liquids should not be stored or chilled in domestic refrigerators and freezers but in units specifically designed for this purpose. It is acceptable to store or chill flammable in ultra-low temperature units. |
If flammable liquids will be placed in ovens, make sure they are appropriately designed for flammable liquids (no internal ignition sources and/or vented mechanically). |
HIGHLY REACTIVE CHEMICALS & HIGH ENERGY OXIDIZERS |
General Information |
Highly reactive chemicals include those which are inherently unstable and susceptible to rapid decomposition as well as chemicals which, under specific conditions, can react alone, or with other substances in a violent uncontrolled manner, liberating heat, toxic gases, or leading to an explosion. Reaction rates almost always increase dramatically as the temperature increases. Therefore, if heat evolved from a reaction is not dissipated, the reaction can accelerate out of control and possibly result in injuries or costly accidents. |
Air, light, heat, mechanical shock (when struck, vibrated or otherwise agitated), water, and certain catalysts can cause decomposition of some highly reactive chemicals, and initiate an explosive reaction. Hydrogen and chlorine react explosively in the presence of light. Alkali metals, such as sodium, potassium and lithium, react violently with water liberating hydrogen gas. Examples of shock sensitive materials include acetylides, azides, organic nitrates, nitro compounds, and many peroxides. |
Organic peroxidesare a special class of compounds that have unusual stability problems, making them among the most hazardous substances normally handled in the laboratories. As a class, organic peroxides are low powered explosives. Organic peroxides are extremely sensitive to light, heat, shock, sparks, and other forms of accidental ignition; as well as to strong oxidizing and reducing materials. All organic peroxides are highly flammable. |
Peroxide formers can form peroxides during storage and especially after exposure to the air (once opened). Peroxide forming substances include: aldehydes, ethers (especially cyclic ether), compounds containing benzylic hydrogen atoms, compounds containing the allylic structure (including most alkenes), vinyl and vinylidine compounds. |
Examples of shock sensitive chemicals, high energy oxidizers and substances which can form explosive peroxides are listed at the end of this section. |
Special Handling Procedures |
Before working with a highly reactive material or high energy oxidizer, review available reference literature to obtain specific safety information. The proposed reactions should be discussed with your supervisor. Always minimize the amount of material involved in the experiment; the smallest amount sufficient to achieve the desired result should be used. Scale-ups should be handled with great care, giving consideration to the reaction vessel size and cooling, heating, stirring and equilibration rates. |
Excessive amounts of highly reactive compounds should not be purchased, synthesized, or stored in the laboratories. The key to safely handling reactive chemicals is to keep them isolated from the substances that initiate their violent reactions. Unused peroxides should not be returned to the original container. |
Do not work alone. All operations where highly reactive and explosive chemicals are used should be performed during the normal work day or when other employees are available either in the same laboratory or in the immediate area. |
Perform all manipulations of highly reactive or high energy oxidizers in a chemical fume hood. (Some factors to be considered in judging the adequacy of the hood include its size in relation to the reaction and required equipment, the ability to fully close the sash, and the composition of the sash.) |
Make sure that the reaction equipment is properly secured. Reaction vessels should be supported from beneath with tripods or lab jacks. Use shields or guards which are clamped or secured. |
If possible, use remote controls for controlling the reaction (including cooling, heating and stirring controls). These should be located either outside the hood or at least outside the shield. |
Handle shock sensitive substances gently, avoid friction, grinding, and all forms of impact. Glass containers that have screw-cap lids or glass stoppers should not be used. Polyethylene bottles that have screw-cap lids may be used. Handle water-sensitive compounds away from water sources. Light-sensitive chemicals should be used in light-tight containers. Handle highly reactive chemicals away from the direct light, open flames, and other sources of heat. Oxidizing agents should only be heated with fiberglass heating mantles or sand baths. |
High energy oxidizers, such as perchloric acid, should only be handled in a wash down hood if the oxidizer will volatilize and potentially condense in the ventilation system. Inorganic oxidizers such as perchloric acid can react violently with most organic materials. |
When working with highly reactive compounds and high energy oxidizers, always wear the following personal protection equipment: lab coats, gloves, and protective glasses/goggles. During the reaction, a face shield long enough to give throat protection should be worn. |
Labels on peroxide forming substances should contain the date the container was received, first opened and the initials of the person who first opened the container. They should be checked for the presence of peroxides before using, and quarterly while in storage (peroxide test strips are available). If peroxides are found, the materials should be decontaminated, if possible, or disposed of. The results of any testing should be placed on the container label. Never distill substances contaminated with peroxides. Peroxide forming substances that have been opened for more than one year should be discarded. Never use a metal spatula with peroxides. Contamination by metals can lead to explosive decompositions. |
Store highly reactive chemicals and high energy oxidizers in closed cabinets segregated from the materials with which they react and, if possible, in secondary containers. You can also store them in the cabinet under a hood. Do not store these substances above eye level or on open shelves. |
Store peroxides and peroxide forming compounds at the lowest possible temperature. If you use a refrigerator, make sure it is appropriately designed for the storage of flammable substances. Store light-sensitive compounds in the light-tight containers. Store water-sensitive compounds away from water sources. |
Shock sensitive materials should be discarded after one year if in a sealed container and within six months of opening unless an inhibitor was added by the manufacturer. |
List of Shock Sensitive Chemicals |
Shock sensitive refers to the susceptibility of the chemical to rapidly decompose or explode when struck, vibrated or otherwise agitated. The following are examples of materials which can be shock sensitive: |
Acetylides of heavy metals Heavy metal azides Picramic acid |
Aluminum ophrite explosive Hexanite Picramide |
Amatol Hexanitrodiphenylamine Picratol |
Ammonal Hexanitrostilbene Picric acid |
Ammonium nitrate Hexogen Picryl chloride |
Ammonium perchlorate Hydrazinium nitrate Picryl fluoride |
Ammonium picrate Hyrazoic acid Polynitro aliphatic compounds |
Ammonium salt lattice Lead azide Potassium nitroaminotetrazole |
Butyl tetryl Lead mannite Silver acetylide |
Calcium nitrate Lead mononitroresorcinate Silver azide |
Copper acetylide Lead picrate Silver styphnate |
Cyanuric triazide Lead salts Silver tetrazene |
Cyclotrimethylenetrinitramine Lead styphnate Sodatol |
Cyclotetramethylenetranitramine Trimethylolethand Sodium amatol |
Dinitroethyleneurea Magnesium ophorite Sodium dinitro-orthocresolate |
Dinitroglycerine Mannitol hexanitrate Sodium nitrate-potassium |
Dinitrophenol Mercury oxalate Sodium picramate |
Dinitrophenolates Mercury tartrate Styphnic acid |
Dinitrophenyl hydrazine Mononitrotoluene Tetrazene |
Dinitrotoluene Nitrated carbohydrate Tetranitrocarbazole |
Dipicryl sulfone Nitrated glucoside Tetrytol |
Dipicrylamine Nitrated polyhydric alcohol Trimonite |
Erythritol tetranitrate Nitrogen trichloride Trinitroanisole |
Fulminate of mercury Nitrogen tri-iodide Trinitrobenzene |
Fulminate of silver Nitroglycerin Trinitrobenzoic acid |
Fulminating gold Nitroglycide Trinitrocresol |
Fulminating mercury Nitroglycol Trinitro-meta-cresol |
Fulminating platinum Nitroguanidine Trinitronaphtalene |
Fulminating silver Nitroparaffins Trinitrophenetol |
Gelatinized nitrocellulose Nitronium perchlorate Trinitrophloroglucinol |
Germane Nitrourea Trinitroresorcinol |
Guanyl nitrosamino Organic amine nitrates Tritonal |
guanyl-tetrazene Organic nitramines Urea nitrate |
Guanyl nitrosaminoguanylidene-hydrazine Organic peroxides |
List of High Energy Oxidizers |
The following are examples of materials which are powerful oxidizing reagents: |
Ammonium permaganate Fluorine Potassium perchlorate |
Barium peroxide Hydrogen peroxide Potassium peroxide |
Bromine Magnesium perchlorate Propyl nitrate |
Calcium chlorate Nitric acid Sodium chlorate |
Calcium hypochlorite Nitrogen peroxide Sodium chlorite |
Chlorine trifluoride Perchloric acid Sodium perchlorate |
Chromium anhydride or chromic acid Potassium bromate Sodium Peroxide |
List of Peroxide Formers |
The following are examples of the materials commonly used in laboratories which may form explosive peroxides: |
Acetal Dimethyl ether Sodium amide |
Cyclohexene Dioxane Tetrahydrofuran |
Decahydronaphthalene Divinyl acetylene Tetrahydronaphthalene |
Diacetylene Ether (glyme) Vinyl ethers |
Dicyclopentadiene Ethylene glycol dimethyl ether Vinylidene chloride |
Diethyl ether Isopropyl ether |
Diethylene glycol Methyl acetylene |
COMPRESSED GASES |
General Information |
Compressed gases are unique in that they represent both a physical and a potential chemical hazard (depending on the particular gas). Gases contained in cylinders may be from any of the hazard classes described in this section (flammable, |
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HEALTH AND SAFETY INFORMATION FOR WORK WITH CHEMICALS OF SPECIFIC HAZARD CLASS
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