GENERAL LAB SAFETY

LABORATORY GENERAL SAFETY HAZARDS


Accidents in the laboratory are often the result of carelessness or ignorance either by you or by your neighbors. Stay alert and pay constant attention to your own and to your neighbors' actions. The safety precautions outlined below will be worthless unless you plan, understand, and think through the consequences of every operation before you perform it. The common accidents, which often occur simultaneously, are fire, explosion, chemical and thermal burns, cuts from broken glass tubing and thermometers, absorption of toxic, but non-corrosive chemicals through the skin, and inhalation of toxic fumes. Less common, but obviously dangerous, is the ingestion of a toxic chemical. Each of these types is discussed in a general way below, and more specific reference to certain hazards will be found in the individual experiments.

1. Fire: There should never be open flames in the lab. Make it a working rule that water is the only nonflammable liquid you are likely to encounter. Treat all others in the vicinity of a flame as you would gasoline.  
Display "No smoking signs" , visible all around.

It is your responsibility to yourself and to your neighbors to know where the nearest safety shower and fire extinguisher are located. 


2. Explosion. Never heat a closed system or conduct a reaction in a closed system.  Before starting a distillation or a chemical reaction, make sure that the system is vented. The results of an explosion are flying glass and spattered chemicals, usually both hot and corrosive.


3. Chemical and Thermal Burns: Be aware of the chemicals' properties and always use protective equipment.
Be careful with hot plates to avoid burns. Always assume that hot plates are HOT. 


4. Cuts:. The most common laboratory accident is probably the cut received while attempting to force a cork or rubber stopper onto a piece of glass tubing, a thermometer, or the side-arm of a distilling flask. Be sure to make a proper-sized hole, lubricate the cork or stopper (lubrication is essential with a rubber stopper), and use a gentle pressure with rotation on the glass part. Severed nerves and tendons are common results of injuries caused by improper manipulation of glass tubes and thermometers. Always pull rather than push on the glass when possible.


5. Absorption of Chemicals: Keep chemicals off the skin. Many organic substances are not corrosive, do not burn the skin, or seem to have any serious effects. They are, however, absorbed through the skin, sometimes with dire consequences. Others will give a serious allergic reaction upon repeated exposure, as evidenced by severe dermatitis. Be careful about touching your face or eyes in the lab; make sure your hands are clean first. Gloves will be available in the lab. However, gloves provide only a temporary layer of protection against chemicals on your skin and may be permeable to some chemical reagents, without visible deterioration. If your gloves come in contact with a chemical reagent, remove them, wash your hands, and get a new pair immediately.


6. Inhalation of Chemicals: Keep your nose away from chemicals. Many of the common solvents are extremely toxic if inhaled in any quantity or over a period of time. Do not evaporate excess solvents in the laboratory; use the hood or a suitable distillation apparatus with a condenser.  Specific safety information about chemicals used is included in each experiment write up. 


7. Ingestion of Chemicals: The common ways of accidentally ingesting harmful chemicals are: (1) by pipet, (2) from dirty hands, (3) contaminated food or drink and (4) food use of chemicals taken from the laboratory. Below are ways to avoid accidental ingestion of chemical reagents.


• Pipets must be fitted with suction bulbs to transfer chemicals. DO NOT USE MOUTH SUCTION.


• Wash your hands before handling anything (cigarettes, chewing gum, food) which goes into your mouth. Wash your hands when you leave the laboratory. 


• Do not eat or drink in the laboratory:  Use the water fountains for a drink--not a laboratory faucet. Remove gloves and wash your hands before using the water fountain or bathroom.

• Never use chemicals (salt, sugar, alcohol, bicarbonate, etc.) from the laboratory or stockroom on food. The source containers may be contaminated or mislabeled.


• Never use laboratory glassware as a food or drink container.


• Never store food or drink in a laboratory refrigerator or ice machine. Never consume ice from a laboratory ice machine.


GENERAL SAFETY RULES


Know the locations of the eyewash fountain, safety shower, fire blanket, and the fire extinguisher nearest to your laboratory bench. Be sure to know how to use this safety equipment. Your action during an emergency might prevent a classmate from serious injury.


WEAR SAFETY GLASSES AT ALL TIMES IN THE LABORATORY. 

Goggles are required to be worn at all times! Goggles are available to be worn over prescription glasses. 


WEAR SENSIBLE CLOTHING 
In the laboratory, sensible clothing includes shoes that fully cover the feet; protects from unseen hazards on the floor. Sensible clothing also includes old clothes, which are not too loose, especially at the sleeves. Laboratory coats or aprons are even more satisfactory.  Do not wear synthetics clothes if possible as they burn readily.

NEVER WORK ALONE IN THE LABORATORY
All work must be performed under the supervision of a laboratory instructor/demonstrator. The instructor should be aware of the exact nature of all work being done in the laboratory.


DO NOT PERFORM ANY UNAUTHORIZED EXPERIMENTS
Do only the experiment, which has been assigned by the laboratory instructor. Never do any unauthorized experiment/test in place of the one assigned by the instructor/supervisor. 

DO NOT EAT, DRINK OR SMOKE IN THE LABORATORY 
For safety purposes, assume all chemicals to be poisonous either by themselves or because of impurities. Also avoid direct contact with organic chemicals. Many are absorbed directly through the skin.


KEEP THE LABORATORY CLEAN AT ALL TIMES 
Any chemical spilled on your skin or your clothing, should be washed immediately and thoroughly. If a solution, a solid, or liquid chemical is spilled on the bench or on the laboratory floor, clean up the spill immediately. Make sure that your work area is clean and free of spilled chemicals or scraps of paper. Wash your hands with soap and water.


DISPOSE OF WASTE AND EXCESS MATERIALS IN THE PROPER MANNER
Used matches, paper, broken glass, or porcelain ware should be placed in the appropriate containers but not in the sinks or cup sinks. If you have any questions concerning the waste disposal, ask your instructor for the proper procedure.


USE THE FUME HOOD WHEN NECESSARY 
Use the fume hood when you are so directed, Fume hoods remove toxic vapors and irritating odors from the laboratory. The removal of these materials is essential for protecting the health and safety of those people working in the laboratory.


NEVER LOOK DIRECTLY into the mouth of an open flask or test tube if it contains a reaction mixture.


USE ONLY EQUIPMENT, WHICH IS IN GOOD CONDITION:   Defective equipment is an important source of 


GLOVES

Glove Types and Removal Gloves should be selected on the basis of the material being handled and the particular hazard involved. 
.
MIXING
If liquid chemicals are to be mixed with water, always add the concentrated chemical to water rather than the other way around. This keeps the new solution dilute at all times and avoids many accidents. Usually addition should be done slowly, using small quantities. It is especially important to add acid to water because of the heat generated.


DISPOSAL 
If the laboratory instructor directs you to dispose of any solid chemicals in the skin, flush it down the drain with copious amounts of running water. All other solids should be disposed of in special containers provided for this purpose.


IF AN ACCIDENT OCCURS
In spite of the best efforts of all concerned, accidents sometimes occur in the laboratory. Use good judgment and do not panic in case of an emergency. 


CHEMICAL SPILLS:
Locate spill cleanup materials. Laboratories should be equipped with spill cleanup kits. 
Wear the appropriate personal protective equipment (e.g., gloves, goggles) when cleaning up spills.

Acid Spills: 
Apply neutralizer (or sodium bicarbonate) to perimeter of spill. Mix thoroughly until fizzing and evolution of gas ceases. NOTE: It may be necessary to add water to the mixture to complete the reaction. Neutralizer has a tendency to absorb acid before fully neutralizing it. Check mixture with pH indicator paper to assure that the acid has been neutralized. 
Transfer the mixture to a plastic bag, tie shut, fill out a waste label, and place in the fume hood. Notify supervisor.
Caustic Spills
Apply neutralizer to perimeter of spill. Mix thoroughly until fizzing and evolution of gas ceases. Check mixture with pH indicator paper to assure that the material has been completely neutralized. 
Transfer the mixture to a plastic bag, tie shut, fill out a waste label, and place in the fume hood. Notify supervisor.
Solvent Spills 
Apply activated charcoal to the perimeter of the spill. Mix thoroughly until material is dry and no evidence of liquid solvent remains.
Transfer absorbed solvent to a plastic bag (if compatible), tie shut, fill out and attach a waste label, and place in the fume hood. Notify supervisor.
Mercury Spills 
Using a mercury vacuum, vacuum all areas where mercury was spilled with particular attention to corners, cracks, depressions and creases in flooring or table tops. Place the contaminated sponge in its plastic bag, tie shut, fill out and attach a waste label, and place in the fume hood. 


LARGE CHEMICAL SPILLS ON THE LABORATORY BENCH OR AREA


a.   If the material is not particularly volatile, nor toxic, and poses no fire hazard: 
Liquid can be cleaned up by using an absorbent material which neutralizes them, for example, sodium bicarbonate solution or powder for acids, or sodium thiosulfate solution for bromine. Rubber or plastic gloves should be worn while using absorbent materials. A dustpan and brush should be used to remove the absorbent material. Then, the contaminated area should be cleaned with soap or detergent and water; and the area mopped dry.


b.   If the material is volatile, flammable or toxic:
ALERT everyone in the laboratory to extinguish flames, disconnect spark-producing equipment, shut down all experiments, and evacuate the laboratory. The laboratory instructor will handle the clean up.


CHEMICAL SPILLS ON A PERSON


1. OVER A LARGE AREA: Within seconds, quickly remove all contaminated clothing while person is under safety shower. Flood the affected body area with cold water for at least fifteen minutes. If pain continues or resumes, flood with more water. Wash off chemicals with a mild detergent solution. Do not apply any materials such as neutralizing agents or salves, to the area. Obtain medial assistance immediately.

2. OVER A SMALL AREA: Immediately flush area thoroughly with cold water. Wash with a mild detergent solution. If there is no visible burn, scrub the area with warm water and soap.


3. IN THE EYES: You will need to assist the person who has chemicals spattered in the eyes. Immediately drench the eyes at the nearest emergency eyewash station. Force the eye or eyes open to get water into them. The speed of your response to this emergency is extremely important. Notify the laboratory instructor/supervisor of the accident immediately.


SWALLOWING CHEMICALS


The laboratory instructor should determine what specific substance ingested. 
The individual should be forced to drink copious amounts of water while en route to medical assistance. The Health Center or Hospital should be notified while the individual is in transit as to what chemicals are involved.


BURNS


For burns by hot objects, flames or chemical, flush the affected area with cold water for several minutes. Notify the laboratory instructor of the burn and he will arrange transportation to the infirmary if necessary.

INJURY OR ILLNESS


Render assistance if necessary. For minor cuts, wash them thoroughly, apply a good antiseptic, and a band-aid. For major cuts, severe bleeding or serious illness, send someone for help and administer first aid. Only a physician is trained to treat serious injury or illness. Notify the instructor immediately.




ELECTRICAL SAFETY 


NEVER WORK ALONE 

PREVENT ACCIDENTS: FOLLOW THIS ADVICE 


•  Never hurry. Work deliberately and carefully. 
•  Connect to the power source LAST. 
•  If  you  are  working  with  a lab kit that has internal power supplies,  turn the main power switch 
OFF  before  you  begin work on the circuits.  Wait a few seconds for power supply capacitors to 
discharge.  These steps will also help prevent damage to circuits. 
•  If  you are working with a circuit that will be connected to an external power supply,  turn the 
power switch of the external supply OFF before you begin work on the circuit. 
•  Check  circuit  power  supply  voltages  for proper value and for type (DC, AC, frequency) before 
energizing the circuit. 
•  Do not run wires over moving or rotating equipment, or on the floor,  or  string  them  across 
walkways from bench-to-bench. 
•  Remove conductive watch bands or chains, finger  rings, wrist watches, etc., and do not use 
metallic pencils, metal  or metal edge rulers, etc. when working with exposed circuits. 
•  When breaking an inductive circuit open the switch with your left hand and turn your face away to 
avoid danger from any arc which may occur across the switch terminals. 
•  When  using large electrolytic capacitors be sure to wait long enough (approximately five time 
constants) for the capacitors to discharge before working on the circuit. 
•  All conducting surfaces intended to be at ground potential should be connected together. 

SAFETY
Safety in the electrical laboratory, as everywhere else, is a matter of the knowledge of
potential hazards, following safety precautions, and common sense. .


Death is usually certain when 0.1 ampere or more flows through the head or upper thorax and have been fatal to persons with coronary conditions. 
The current depends on body resistance, the resistance between body and ground, and the
voltage source. 


If the skin is wet, the heart is weak, the body contact with ground is
large and direct, then 40 volts could be fatal. Therefore, never take a chance on "low"
voltage. 


When working in a laboratory, injuries such as burns, broken bones, sprains, or
damage to eyes are possible and precautions must be taken to avoid these as well as
the much less common fatal electrical shock. 


Make sure that you have handy emergency phone numbers to call for assistance if necessary. If any safety questions arise, consult the lab demonstrator or technical assistant / technician for guidance and
instructions. 


Observing proper safety precautions is important when working in the
laboratory to prevent harm to yourself or others. The most common hazard is the
electric shock which can be fatal if one is not careful.


Acquaint yourself with the location of the following safety items within the lab.


a. fire extinguisher
b. first aid kit
c. telephone and emergency numbers


Electric shock
Shock is caused by passing an electric current through the human body. The severity
depends mainly on the amount of current and is less function of the applied voltage.
The threshold of electric shock is about 1 mA which usually gives an unpleasant
tingling. 
For currents above 10 mA, severe muscle pain occurs and the victim can't let
go of the conductor due to muscle spasm. Current between 100 mA and 200 mA (50 Hz
AC) causes ventricular fibrillation of the heart and is most likely to be lethal.What is the voltage required for a fatal current to flow? This depends on the skin resistance. Wet skin can have a resistance as low as 150 Ohm and dry skin may have a resistance of 15 kOhm. Arms and legs have a resistance of about 100 Ohm and the
trunk 200 Ohm. 
This implies that 240 V can cause about 500 mA to flow in the body if
the skin is wet and thus be fatal. In addition skin resistance falls quickly at the point of
contact, so it is important to break the contact as quickly as possible to prevent the
current from rising to lethal levels.


Equipment grounding
Grounding is very important. Improper grounding can be the source of errors, noise and
a lot of trouble. Here we will focus on equipment grounding as a protection against
electrical shocks. Electric instruments and appliances have equipments casings that are
electrically insulated from the wires that carry the power. The isolation is provided by the
insulation of the wires as shown in the figure a below. However, if the wire insulation
gets damaged and makes contact to the casing, the casing will be at the high voltage
supplied by the wires. If the user touches the instrument he or she will feel the high
voltage.

If, while standing on a wet floor, a user simultaneously comes in contact with
the instrument case and a pipe or faucet connected to ground, a sizable current can
flow through him or her, as shown in Figure b. However, if the case is connected to the
ground by use of a third (ground) wire, the current will flow from the hot wire directly to
the ground and bypass the user as illustrated in figure c.


Equipments with a three wire cord is thus much safer to use. The ground wire (3rd wire)
which is connected to metal case, is also connected to the earth ground (usually a pipe
or bar in the ground) through the wall plug outlet.Always observe the following safety precautions when working in the laboratory:


OBSERVE THE FOLLOWING RULES:-


1. Do not work alone while working with high voltages or on energized electrical
equipment or electrically operated machinery like a drill.
2. Power must be switched off whenever an experiment or project is being
assembled, disassembled, or modified. Discharge any high voltage points to
grounds with a well insulated jumper. Remember that capacitors can store
dangerous quantities of energy.
3. Make measurements on live circuits or discharge capacitors with well insulated
probes keeping one hand behind your back or in your pocket. Do not allow any part
of your body to contact any part of the circuit or equipment connected to the circuit.
4. After switching power off, discharge any capacitors that were in the circuit. Do not
trust supposedly discharged capacitors. Certain types of capacitors can build up a
residual charge after being discharged. Use a shorting bar across the capacitor, and
keep it connected until ready for use. If you use electrolytic capacitors, do not :
· put excessive voltage across them
· put ac across them
· connect them in reverse polarity
5. Take extreme care when using tools that can cause short circuits if accidental
contact is made to other circuit elements. Only tools with insulated handles should
be used.
6. If a person comes in contact with a high voltage, immediately shut off power. Do not
attempt to remove a person in contact with a high voltage unless you are insulated
from them. If the victim is not breathing, apply CPR immediately continuing until
he/she is revived, and have someone dial emergency numbers for assistance.
7. Check wire current carrying capacity if you will be using high currents. Also make
sure your leads are rated to withstand the voltages you are using. This includes
instrument leads.
8. Avoid simultaneous touching of any metal chassis used as an enclosure for your
circuits and any pipes in the laboratory that may make contact with the earth, such
as a water pipe. Use a floating voltmeter to measure the voltage from ground to the
chassis to see if a hazardous potential difference exists.
9. Make sure that the lab instruments are at ground potential by using the ground
terminal supplied on the instrument. Never handle wet, damp, or ungrounded
electrical equipment.
10. Never touch electrical equipment while standing on a damp or metal floor.
11. Wearing a ring or watch can be hazardous in an electrical lab since such items make
good electrodes for the human body.
12. When using rotating machinery, place neckties or necklaces inside your shirt or,
better yet, remove them.
13. Never open field circuits of D-C motors because the resulting dangerously high
speeds may cause a "mechanical explosion".
14. Keep your eyes away from arcing points. High intensity arcs may seriously impair
your vision or a shower of molten copper may cause permanent eye injury.
15. Never operate the black circuit breakers on the main and branch circuit panels.
16. In an emergency all power in the laboratory can be switched off by depressing the
large red button on the main breaker panel. Locate it. It is to be used for
emergencies only.
17. Chairs and stools should be kept under benches when not in use. Sit upright on
chairs or stools keeping the feet on the floor. Be alert for wet floors near the stools.
18. Horseplay, running, or practical jokes must not occur in the laboratory.
19. Never use water on an electrical fire. If possible switch power off, then use CO2 or a
dry type fire extinguisher. Locate extinguishers and read operating instructions
before an emergency occurs.
20. Never plunge for a falling part of a live circuit such as leads or measuring equipment.
21. Never touch even one wire of a circuit; it may be hot.
22. Avoid heat dissipating surfaces of high wattage resistors and loads because they
can cause severe burns.
23. Keep clear of rotating machinery.Precautionary Steps Before Starting an Experiment so as Not to Waste Time Allocated.