Laboratory Safety Rules

Electric Shocks

It might seem that a shock of 10,000 volts would be more deadly than one of 100 volts, but this is not necessarily the case. Individuals have been electrocuted by appliances using ordinary household currents of 110 volts, and by electrical apparatus in industry using as little as 42 volts direct current. The real measure of shock intensity lies in the amount of current forced through the body, and not the voltage. Any electrical device using a house wiring circuit can under certain conditions transmit a fatal current.

While any amount of current more than 10 mA is capable of producing painful to severe shock, currents between 100 mA and 200 mA are lethal. At values as low as 20 mA, breathing becomes labored, finally ceasing completely at values about 75 mA. As the current approaches 100 mA, ventricular fibrillation of the heart occurs. This is an uncoordinated twitching of the walls of the heart ventricles that can quickly lead to death. Currents about 200 mA, while producing severe burns and unconsciousness, do not usually cause death if the victim is given immediate medical attention. That is because for currents above 200 mA, the muscular contractions are so severe that the heart is forcibly clamped during the shock. This clamping actually protects the heart from going into ventricular fibrillation.

The actual resistance of the body varies on the points of contact and the skin condition (wet or dry). The skin resistance may vary from 100 W for wet skin to more than 500,000 W for dry skin. Do not touch electrical equipment while standing on metal floors, damp concrete, or other well-grounded surfaces. Do not handle electrical equipment while wearing damp clothing (particularly wet shoes) or while skin surfaces are damp.

If you observe an individual being electrically shocked, cut the voltage and/or remove the victim from contact as quickly as possible, but without endangering your own safety. Use a length of dry wood, rope, blanket, etc., to pry or pull the victim loose. Do not waste valuable time looking for the power switch. The resistance of victim decreases with time, and fatal 100 to 200 mA level may be reached if action is delayed. If the victim is unconscious and has stopped breathing, start artificial respiration at once. Do not stop resuscitation until medical help arrives.

In the event of a major emergency it is important to alert the proper authorities immediately. In order to contact off-campus emergency personnel by telephone, dial 175 for Fire and Rescue. Telephones are located in all ME faculty offices, in Wing C, and in the main ME office. The AUB emergency numbers are: 5555 (Fire), 2400 (Protection Office), and 2360 (Environmental Health and Safety Center). Fire alarms are located at both ends of the Wing C.

Laboratory Safety

Safe conduct of the laboratory experiments is of paramount importance in ME 117. The laboratory experiments to be performed by students have been designed with safety in mind. However, in order to avoid the possibility of injuries, it is important that the students be aware of their surroundings and pay attention to all instructions. It is always possible that unforeseen events may lead to circumstances that are potentially dangerous. In that case prompt and correct response can minimize the potential for personal injury.

Minor Cuts

In the event that minor cuts or burns are experienced in the laboratory, a first aid kit is mounted on the wall of the mechatronics laboratory (Wing C). The kit contains variety of bandages, antiseptic wipes, etc. and instructions for simple medical procedures. Quickly inform the instructor if minor medical attention is required.

Safety Glasses

Students should use safety glasses. Their use is mandatory in situations where chemicals can be splashed into the eyes or where solid particles may enter the eye. Safety glasses are designed so that they could be worn over prescription lenses. If your eyes are exposed to any solid particles or liquid splatters, contact the instructor immediately. An eyewash station is located near the entrance in Wing C, if necessary.

Fire Safety

Fire extinguishers carry classifications on their nameplates that consist of a numeral followed by a letter. The numeral indicates the approximate relative fire extinguishing capacity on that class of fire, which is identified by the letter. Class A fires involve ordinary combustible materials such as paper, wood, fabrics, rubber, and many plastics. Quenching by water or Halon 1211, or insulating by a multipurpose chemical agent, is effective. Class B fires occur in flammable liquids such as gasoline, oils, greases, tars, paints, lacquers, and flammable gases. Dry chemicals, Halon 1211, and carbon dioxide agents extinguish these fires. Class C fires take place in electrical equipment such as motors, generators, switches, and appliances. Nonconducting extinguishing agents such as dry chemicals, Halon 1211, or carbon dioxide are required to extinguish them.

A CO2 fire extinguisher (Class BC) is located on the floor along the west wall in the mechatronics laboratory. A water stream extinguisher (Class A) is mounted on the wall in the hallway leading to the mechatronics laboratory. In order to actuate a fire extinguisher, follow the instructions written on the device. It is typically necessary to be fairly close to the fire, i.e., within approximately 10 feet. Always direct the extinguisher stream to the base of the flames. This will remove the oxygen source and smother the flames.

Use Common Sense

Most often safety in the laboratory can be insured if simple, common sense rules are strictly applied. For example, inappropriate behavior in the laboratory can be dangerous, and will not be tolerated. It is important that students never work alone. Be careful when using glassware in the laboratory, due to the possibility of breakage. In particular, thermometers are quite fragile, and should not be employed as stirring rods. Never bend or kink the power cord on an instrument, as this can crack the insulation, thereby introducing the danger of electrical shocks or burns. If it is necessary to use a hot plate in an experiment, it is important that the heating element never come in contact with fingers, clothing, or the power cord of an instrument. Never leave an experiment unattended. Familiarize yourself with the location of all safety devices, and always exercise caution and good judgment.