HEALTH AND SAFETY INFORMATION FOR WORK WITH CHEMICALS OF SPECIFIC HAZARD CLASS

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 peroxides are 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,