SECTION 7: Safe Work Practices and Procedures
General Work Practices
You Begin (top)
Every laboratory worker should observe the following rules:
- Know the potential hazards and appropriate safety precautions
before beginning work. Ask and be able to answer the following questions:
- What are the hazards?
- What are the worst things that could happen?
- What do I need to do to be prepared?
- What work practices, facilities or personal protective equipment
are needed to minimize the risk?
- Know the location and how to use emergency equipment, including
safety showers and eyewash stations.
- Never block safety equipment or doors and keep aisles clear and free from tripping hazards.
- Familiarize yourself with the emergency response procedures, facility
alarms and building evacuation routes.
- Know the types of personal protective equipment available and
how to use them for each procedure.
- Be alert to unsafe conditions and actions and bring them to the
attention of your supervisor or lab manager immediately so that corrections
be made as soon as possible.
- Prevent pollution by following waste
disposal procedures. Chemical reactions may require traps
or scrubbing devices to prevent the release of toxic substances
to the laboratory
or to the environment.
- Position and clamp reaction apparatus thoughtfully in order to
permit manipulation without the need to move the apparatus until
reaction is completed. Combine reagents in the appropriate order
and avoid adding solids to hot liquids.
Many local, state and federal regulations have specific requirements that
affect the handling and storage of chemicals in laboratories.
In general, store materials and equipment in cabinets and on shelving provided
for such storage.
- Avoid storing materials and equipment on top of cabinets. If you
must place things there, however, you must maintain a clearance of at
least 18 inches from the sprinkler heads or (if no sprinkler heads
are present) 24 inches from the ceiling.
- Be sure that the weight of the chemicals does not exceed the load
capacity of the shelf or cabinet. Some incidents where shelving or a
cabinet collapsed due to overload are described in Anecdotes.
- Wall-mounted shelving must have heavy-duty brackets and standards.
This type of shelving is not recommended for chemical storage.
- Cabinets for chemical storage must be of solid, sturdy construction,
preferably hardwood or metal.
- Do not store materials on top of high cabinets where they will
be hard to see or reach.
- Do not store corrosive
liquids above eye level.
- Provide a specific storage location for each type of chemical,
and return the chemicals to those locations after each use.
- Avoid storing chemicals in the workspace within a laboratory
hood, except for those chemicals currently in use.
- If a chemical does not require a ventilated cabinet, store it
inside a closable cabinet or on a shelf that has a lip to prevent
from sliding off in the event of an accident or fire.
- Do not expose chemicals to heat or direct sunlight.
- Observe all precautions regarding the storage of incompatible
- Use corrosion resistant storage trays or secondary containers
to collect materials if the primary container breaks or leaks.
- Distinguish between refrigerators used for chemical storage and
refrigerators used for food storage. Each refrigerator should be
labeled "No Food"
or "Food Only". Labels are available from EHS by calling 8-5294.
- Do not store flammable liquids in a refrigerator unless it is
approved for such storage. Such refrigerators are designed with non-sparking
components to avoid an explosion.
- Chemical storage cabinets located outside the laboratory (e.g.,
in hallways) should be labeled with the name of the laboratory group
owns and uses it.
Incompatible chemicals should not be stored together. Storing chemicals
alphabetically, without regard to compatibility, can increase the risk of
a hazardous reaction, especially in the event of container breakage. In
addition to the Chemical Compatibility Chart
below, there are several resources available, both in print and on-line,
including the National Oceanic and Atmospheric Administration Chemical
Use common sense when setting up chemical storage. Segregation that disrupts
normal workflow can increase the potential for spills.
There are several possible storage plans for segregation. In general,
dry reagents, liquids and compressed gases should be stored separately,
then by hazard class, then alphabetically (if desired).
Segregate dry reagents as follows:
- Oxidizing salts
- Flammable solids
- Water-reactive solids
- All other solids
Segregate liquids as follows:
Segregate compressed gases as follows:
- Toxic gases
- Flammable gases
- Oxidizing and inert gases
Mixing these chemicals purposely or as a result of a spill can result
in heat, fire, explosion, and/or toxic gases. This is a partial
||Chromic Acid, nitric acid, hydroxyl-containing compounds, ethylene
glycol, perchloric acid, peroxides, and permanganates.
||Bromine, chlorine, nitric acid, sulfuric acid, and hydrogen peroxide.
||Bromine, chlorine, copper, mercury, fluorine, iodine, and silver.
|Alkaline and Alkaline Earth Metals such as calcium, lithium, magnesium,
sodium, potassium, powdered aluminum
||Carbon dioxide, carbon tetrachloride and other chlorinated hydrocarbons,
water, Bromine, chlorine, fluorine, and iodine. Do
not use CO2, water or dry chemical extinguishers. Use Class
D extinguisher (e.g., Met-L-X) or dry sand.
|Aluminum and its Alloys (especially powders)
||Acid or alkaline solutions, ammonium persulfate and water, chlorates,
chlorinated compounds, nitrates, and organic compounds in nitrate/nitrate
||Bromine, chlorine, calcium hypochlorite, hydrofluoric acid, iodine,
mercury, and silver.
||Acids, metal powders, flammable liquids, chlorates, nitrates,
sulfur and finely divided organics or other combustibles.
||Hydrogen peroxide or nitric acid.
||Acetone, acetylene, ammonia, benzene, butadiene, butane and other
petroleum gases, hydrogen, finely divided metals, sodium carbide,
||Calcium hypochlorite, all oxidizing agents.
||Acids (organic and inorganic).
|Chlorates or Perchlorates
||Acids, aluminum, ammonium salts, cyanides, phosphorous, metal
powders, oxidizable organics or other combustibles, sugar, sulfides,
||Acetone, acetylene, ammonia, benzene, butadiene, butane and other
petroleum gases, hydrogen, finely divided metals, sodium carbide,
||Ammonia, methane, phosphine, hydrogen sulfide.
||Acetic acid, naphthalene, camphor, alcohol, glycerine, turpentine
and other flammable liquids.
||Acetylene, hydrogen peroxide.
||Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid,
sodium peroxide, bromine, chlorine, fluorine, iodine.
||Isolate from everything.
||Hydrogen peroxide, nitric acid, and other oxiding agents.
||Bromine, chlorine, chromic acid, fluorine, hydrogen peroxide,
and sodium peroxide.
||Nitric acid, alkali.
||Ammonia, aqueous or anhydrous.
|Hydrogen Peroxide (anhydrous)
||Chromium, copper, iron, most metals or their salts, aniline, any
flammable liquids, combustible materials, nitromethane, and all
other organic material.
||Fuming nitric acid, oxidizing gases.
||Acetylene, ammonia (aqueous or anhydrous), hydrogen.
||Acetylene, alkali metals, ammonia, fulminic acid, nitric acid
with ethanol, hydrogen, oxalic acid.
||Combustible materials, esters, phosphorous, sodium acetate, stannous
chloride, water, zinc powder.
|Nitric acid (concentrated)
||Acetic acid, acetone, alcohol, aniline, chromic acid, flammable
gases and liquids, hydrocyanic acid, hydrogen sulfide and nitratable
||Potassium or sodium cyanide.
||Inorganic bases, amines.
||Silver, mercury, and their salts.
|Oxygen (liquid or enriched air)
||Flammable gases, liquids, or solids such as acetone, acetylene,
grease, hydrogen, oils, phosphorous.
||Acetic anhydride, alcohols, bismuth and its alloys, paper, wood,
grease, oils or any organic materials and reducing agents.
||Acid (inorganic or organic). Also avoid friction and store cold.
||Alcohols, strong bases, water.
||Air (moisture and/or oxygen) or water, carbon tetrachloride, carbon
||Sulfuric and other acids.
||Benzaldehyde, ethylene glycol, glycerol, sulfuric acid.
|Silver and silver salts
||Acetylene, oxalic acid, tartaric acid, fulminic acid, ammonium
||See Alkali Metals
||Acids, ammonium salts, oxidizable materials and sulfur.
||Ammonia compounds, ammonium nitrate, or other ammonium salts.
||Any oxidizable substances, such as ethanol, methanol, glacial
acetic acid, acetic anhydride, benzaldehyde, carbon disulfide, glycerol,
ethylene glycol, ethyl acetate, methyl acetate, furfural, etc.
||Any oxidizing materials.
||Chlorates, perchlorates, permanganates, compounds with light metals
such as sodium, lithium, and potassium.
||Acetyl chloride, alkaline and alkaline earth metals, their hydrides
and oxides, barium peroxide, carbides, chromic acid, phosphorous
oxychloride, phosphorous pentachloride, phosphorous pentoxide, sulfuric
acid, sulfur trioxide.
Flammable liquids require special storage considerations. See Flammable
Materials for more information.
Mineral acids, including phosphoric,
hydrochloric, nitric, sulfuric, and perchloric acid can be stored in
cabinet designed for Corrosive Acids. These non-metallic cabinets
have no internal metallic parts, acid resistant coating and a cabinet
floor constructed to be able to contain spillage. Volatile
acids, such as oleum or fuming nitric acid, should be stored
either in an acid cabinet or in a vented cabinet, such as the fume
particularly after they have been opened. Concentrated mineral
acids can be very reactive, even with each other. Concentrated
acids can even react vigorously with dilute solutions of the
same acid, if mixed together rapidly. For example: concentrated sulfuric
acid mixed quickly with 1 molar sulfuric acid will generate a lot of heat.
Different concentrated acids should be stored apart. If stored within
the same cabinet, plastic trays, tubs or buckets work well to keep different
acids apart within the cabinet.
Acetic acid is an organic acid
and should be stored separately from mineral acids. Since it
is also flammable, it is best stored with other flammable liquids.
Picric Acid can
form explosive salts with many metals, or by itself when dry. Perchloric
Acid is an extremely powerful oxidizer and must be kept
away from all organic materials, including wood. See Section
7d, Corrosives for more information.
Ethers and some ketones and olefins may form peroxides when exposed to air
or light. Since they may have been packaged in an air atmosphere, peroxides
can form even if the container has not been opened.
Some chemicals, such as dinitroglycerine and germane, are shock-sensitive,
meaning that they can rapidly decompose or explode when struck, vibrated
or otherwise agitated. These compounds become more shock-sensitive with
For any potentially unstable chemical:
- On the label, write the date the container was received and the
date it was opened.
- Discard containers within 6 months of opening them.
- Discard unopened containers after one year, unless an inhibitor
More information about unstable chemicals is available in Peroxide
Forming Compounds and Reactives.
Any area where particularly hazardous substances, including carcinogens,
acutely toxic chemicals and reproductive toxins, are stored or used must
be posted as a Designated
Area. These materials should be stored separately from other chemicals,
as space permits. See Particularly
Hazardous Substances for more information.
Compressed gases pose a chemical hazard due to the gases themselves and
a high energy source hazard due to the great amount of pressure in the cylinder.
Large cylinders may weight 130 pounds or more and can pose a crush hazard
to hands and feet.
- All cylinders must be secured to a wall, bench or other support
structure using a chain or strap. Alternatively, a cylinder stand
may be used.
- Segregate cylinders by gas type (e.g., flammable, inert, etc.).
- Store cylinders away from heat sources and extreme weather conditions.
Gas Cylinders for more information.
Common combustible materials, such as paper, wood, corrugated cardboard
cartons and plastic labware, if allowed to accumulate, can create a significant
fire hazard in the laboratory. Combustible materials not stored in metal
cabinets should be kept to a minimum. Store large quantities of such supplies
in a separate room, if possible.
Professional standards of personal behavior are required in any laboratory:
- Avoid distracting or startling other workers
- Do not allow practical jokes or horseplay
- Use laboratory equipment only for its designated purpose
- Do not allow visitors, including children and pets, in laboratories
where hazardous substances are stored or are in use or hazardous
are in progress.
- Do not prepare, store (even temporarily), or consume food or beverages
in any chemical laboratory
- Do not smoke in any chemical laboratory. Additionally, be aware
that tobacco products in opened packages can absorb chemical vapors.
- Do not apply cosmetics when in the laboratory
- Never wear or bring
lab coats or jackets into areas where food is consumed.
- Confine long hair and loose clothing in the laboratory. Wear shoes
at all times. Open-toed shoes or sandals are not appropriate.
- Under no circumstances should mouth suction be used to pipette
chemicals or to start a siphon. Use a pipette bulb or a mechanical
to provide a vacuum.
- Wash well before leaving the laboratory. Do not use solvents for
- Keep work areas clean and free from obstruction. Clean
up spills immediately.
- Do not block access to exits, emergency equipment, controls, electrical
- Avoid working alone.
Spills and chemical exposure can occur if chemicals are transported incorrectly,
even when moving chemicals from one part of the laboratory to another. One
example of such an incident is described in Anecdotes.
To avoid this type of incident, consider the following:
- Use a bottle carrier, cart or other secondary container when transporting
chemicals in breakable containers (especially 250 ml or more) through
hallways or between buildings. Secondary containers are made of rubber,
metal or plastic, with carrying handle(s), and are large enough to
the entire contents of the chemical containers in the event of
breakage. A variety of such containers are available from the Chemistry
or from laboratory supply catalogs.
- Transport of hazardous chemicals in individual containers exceeding
four liters between buildings is strongly discouraged.
- Transportation of hazardous chemicals in personal vehicles is strictly forbidden.
- When moving in the laboratory, anticipate sudden backing up or
changes in direction by others. If you should stumble or fall while
glassware or chemicals, try to project them away from yourself
- The individual transporting the chemical should be knowledgeable
about the hazards of the chemical and should know how to handle a
of the material.
- When transporting compressed
gas cylinders, the cylinder should always be strapped in
a cylinder cart and the valve protected with a cover cap. Do
not attempt to carry
or roll cylinders from one area to another.
- Transport chemicals in freight elevators rather than passenger
elevators, if available.
- Keep chemicals in their original packing when transporting, if
with Scaled-Up Reactions (top)
Scale-up of reactions from those producing a few milligrams or grams to
those producing more than 100g of a product may represent several orders
of magnitude of added risk. The attitudes, procedures and controls applicable
to large-scale laboratory reactions are fundamentally the same as those
for smaller-scale procedures. However, differences in heat transfer, stirring
effects, times for dissolution, and effects of concentration and the fact
that substantial amounts of materials are being used introduce the need
for special vigilance for scaled-up work. Careful planning and consultation
with experienced workers to prepare for any eventuality are essential for
large-scale laboratory work. See Anecdotes.
Although it is not always possible to predict whether a scaled-up reaction
has increased risk, hazards should be evaluated if the following conditions
- The starting material and/or intermediates contain functional
groups that have a history of being explosive (e.g., N—N, N—O, N—halogen, O—O,
and O—halogen bonds) or that could explode to give a large increase
- A reactant or product is unstable near the reaction or work-up
temperature. A preliminary test consists of heating a small sample
in a melting point
- A reaction is delayed; that is, an induction period is required.
- Gaseous by-products are formed.
- A reaction is exothermic. Consider what can be done to provide
cooling if the reaction begins to run away.
- A reaction requires a long reflux period. Consider what could
happen if solvent is lost owing to poor condenser cooling.
- A reaction requires temperatures below 0oC. Consider
what could happen if the reaction warms to room temperature.
In addition, thermal phenomena that produce significant effects on a larger
scale may not have been detected in smaller-scale reactions and therefore
could be less obvious than toxic and/or environmental hazards. Thermal analytical
techniques should be used to determine whether any process modifications
Unattended Experiments (top)
Laboratory operations involving hazardous substances are sometimes carried
out continuously or overnight with no one present. It is the responsibility
of the worker to design these experiments so as to prevent the release of
hazardous substances in the event of interruptions in utility services such
as electricity, cooling water, and inert gas.
- Laboratory lights should be left on, and signs should be posted
identifying the nature of the experiment and the hazardous substances
- If appropriate, arrangements should be made for other workers
to periodically inspect the operation.
- The Emergency Information Poster should
include contact information for the responsible individual in the
event of an emergency.
- Carefully examine how chemicals and apparatus are stored, considering
the possibility for fire, explosion or unintended reactions. A description
of a fire that occurred in a fume hood when an experiment was left
for several days may be found in Anecdotes.
Individuals using hazardous chemicals should not work alone. Another individual
capable of coming to the aid of the worker should be in visual or audio
- If working alone is absolutely necessary, the worker should have
a phone immediately available and should be in contact with another
person (who knows that he or she is being relied upon) at least every
- If no one from the laboratory is available, the worker should coordinate with another person in the building to check in on them periodically.
- If the research or operation is particularly hazardous such that a researcher could be severely injured or overcome by the process, a capable person must be present at all times and know to contact Public Safety at 911 or 258-3333 in event of an emergency.
The laboratory supervisor or PI is responsible for determining whether
the work requires special precautions, such as having two people in the
same room for particular operations.
7B: Flammable Materials
6C: Personal Protective Equipment