BIOLOGY-BASED SAFETY ISSUES
Included in this section:
- Storageof Chemicals
- Fire Prevention
- Eye Protection
- Work Space
- Student Lab Assistants
Storage of Chemicals
The necessity of storing a variety of chemicals with a diversity of properties and reactivities creates special hazards which must be readily recognized and prevented. For more specific information, refer to the Chemistry section in this booklet; Flinn (1998), p. 572 ff.; Gerlovich (1985), pp. 53-71; or Virkus (1978), pp. 37-40.
- Store chemicals by families, not alphabetically. (See references above.)
- Annually inventory all chemicals. Copies of the most current inventory should be kept in the chemical storeroom and in the school’s main office.
- Governmental regulations require an MSDS (Materials Safety Data Sheet) to be on file for every chemical in the lab.
- Label all chemicals: name, chemical formula, date received, and date opened.
- Dispose of unidentifiable or unlabeled chemicals and outdated chemicals in the appropriate manner. Contact the Architect's Office, Department of Environmental Management.
- Known carcinogens should not be kept in schools. See Appendix for list.
- Never add water to acid. Always add small amounts of acid to the water.
- Identify any unstable substances in the lab and take the required precautions. See Virkus (1978), pp. 48-50. The following substances are considered to be unstable. It is suggested that these substances be eliminated from use.
- .. ether
- .. ammonium nitrate
- .. formic acid
- .. sodium, potassium, lithium
- .. phosphorus
- .. ammoniacal silver nitrate solution
- .. benzoyl peroxide
- .. nitrogen tri-iodide
- .. picric acid, metal picrates plus perchloric acid
- .. strong oxidizers including hypochlorite, permanganates, chlorates, and bromates.
- .. cyanides
- Storage rooms are to be kept locked when not in use.
- Students are not to be in the storage room unsupervised.
- Follow recommended procedures for cutting glass tubing with either a file or the hot wire method. See Virkus (1978), p 27 for complete explanation.
- Do not have students insert glass tubing. Teachers should do this procedure.
- Always use glass tubing with fire polished ends. Lubricate glass tubing and stopper hole with glycerin and twist glass tubing into stopper hole. Wrap glass tube with towel or wear gloves.
- Do not use glassware for mixing potentially explosive compounds.
- Always use a bulb to pipette. NEVER pipette with the mouth.
- Frozen glass-to-glass surfaces (e.g., stopcocks or glass-stoppered bottles) can be opened by applying a stream of hot water to the stopper. Either wear gloves or protect the hands with a towel.
- Leave sufficient air space in bottles filled with liquids to allow for expansion.
- Never use laboratory glassware for eating or drinking.
- There should be a separate, labeled, container for broken glass.
- It is always preferable to use a hot plate as a heat source as opposed to an open flame.
- If using alcohol burners, use only alcohol or designated burner fuels. Add some salt to the burner fuel supply to color (orange) the flame. Otherwise, alcohol burner flames tend to be invisible and increase probability of burns.
- Never refill alcohol burners during class.
- Extreme caution should be used with a gas burner. Keep head and clothing away from flame. Turn the flame off when it is not in use.
Autoclaving (Pressure Cooker)
- The teacher should be thoroughly familiar with the operation of the autoclave.
- Examine safety valve and check that it works.
- Tighten wing nuts evenly by tightening down two opposite wing nuts simultaneously.
- Keep the pressure (gauge reading) below twenty pounds.
- Allow the pressure to return to zero before trying to remove the cover.
- Open the test stopcock before releasing the wing nuts.
- Use eye protection when working with autoclave under pressure.
- Sterilization requires 15 minutes at 15 pounds of pressure (psi).
It is the responsibility of each science teacher to act intelligently and immediately in the event of a fire in the classroom. The first concern is to get the students out of the area.
Types of Fires and Fire Extinguishers: There are four general classes of fire. The classification is based on the type of material that is being consumed.
Class A - Paper and trash: wood, textiles, etc.
Class B - Flammable liquid: gasoline, oil, paint, etc.
Class C - Electrical
Class D - Flammable metals: magnesium, sodium, potassium
The use of the appropriate type of extinguisher for each class will provide optimum control. Appropriate extinguishers have been placed in science facilities by the Office of Buildings & Grounds. Questions can be referred to this office.
Class A - Water extinguishers are the most effective and should be used for only Class A fires.
Class B and Class C - Carbon dioxide or dry powder extinguishers containing sodium bicarbonate are effective.
* Carbon dioxide extinguishers are particularly well suited for electrical fires.
* Sodium bicarbonate extinguishers are particularly well suited for flammable liquid fires.
Class D - Flammable metal fires are best extinguished with dry sand or special granular formulations.
Fire Blankets: The proper use of fire blankets should also be demonstrated to students. There is some controversy over whether to use a fire blanket to extinguish a person's skin or clothing. The majority of the evidence suggests that by laying down a person whose clothing is on fire and rolling him/her in a blanket is the safest and most expedient method to use (Gerlovich, 1985). However, the roll need not include a blanket.
Steps In Fire Prevention
· Both the teacher and the students should know the type of fire extinguisher available and its limitations.
· Students should be instructed in how to use a fire extinguisher. Representatives from the local fire department may agree to give a demonstration.
· The ABC type (multi-purpose dry chemical) would be preferred in the biology classroom.
. Never use a carbon dioxide extinguisher on an individual. It could spread the fire and possible cause frostbite.
. The first step in an electrical fire is to pull the plug.
. Both the teacher and the students should know the location of:
.. Fire extinguishers in the classroom
.. Fire extinguishers in the hallway
.. Fire alarms
.. Fire blanket
.Identify the type of fire extinguisher available to you.
.Clearly mark the location of the fire blanket.
.A fire blanket may be used to smother a small fire.
Eye protective equipment appropriate to the course must be provided. The State of Ohio requires that chemical splash goggles be worn by all students if there is any activity occurring anywhere in the lab that poses an eye hazard. This law would include wearing goggles for boiling water or mixing chemicals.
The American National Standards Institute (ANSI) has established criteria for eye protection equipment which is mandated by OSHA. Acceptable goggles bear the logo ANSI "Z87" on both the frame and the lens. Face shields will also display this logo. These goggles are available through the Akron Public Schools Warehouse at a minimal cost. It is the teacher's responsibility to enforce the use of goggles for eye protection.
Students should be instructed at the beginning of the course that they will periodically be required to wear such equipment. Instruction should be repeated each time students are expected to wear eye protection. Students who refuse to wear protective goggles should be removed from the classroom.
There is some controversy concerning the wearing of contact lenses in science labs. Opponents argue that contact lenses will exacerbate a chemical spill or aerosol fumes and will cause damage to the eye. Proponents argue that the physical presence of the contact lens will help protect the cornea.
The American Academy of Opthalmology states that one should analyze the hazards in the workplace and determine on an individual basis whether it is advisable for someone to wear contact lenses. See Gerlovich (1985), p. 137 for the Academy's complete position statement on the use of contact lenses in "industrial settings."
Regardless of the decision that is made, the teacher should know which students are wearing contact lenses. A notation could be made next to the student's name in the grade book or seating chart for easy reference. The teacher will also want written authorization from the student's eye-care professional stating that he/she should be allowed to wear contact lenses in a lab setting.
To facilitate optimum safety precautions for the students, the teacher should be apprised of any allergies or sensitivities that a student may have. These substance reactions and any other relevant medical notations can be made on the student's Safety Contract as the parents sign it.
Students will also be instructed in the proper use of the microscope. These procedures include not focusing in direct sunlight and not raising the objective lens while looking in the eyepiece.
National Science Teachers Association (NSTA) recommends that each student be allowed a minimum of 35 square feet of work space. Overcrowding is especially dangerous in science labs. NSTA also recommends that there should be no more than 24 students per teacher per lab room engaged in a laboratory activity.
Modifications may need to be made for certain handicapped students to accommodate the standard physical set up of the class/lab room. A buddy system may be implemented with a willing, non-handicapped student. Certain procedures and expectations of the handicapped student may also need to be made by the teacher.
Student assistants can be invaluable to a teacher in preparing lab materials, assisting in demonstrations and preparing for lab sessions. Obviously, special attention to safety is necessary for lab assistants. Lab assistants must be carefully selected on the basis of their responsibility, knowledge of the subject, and prior demonstration of consistent adherence to safety practices in the class/lab room(s). Also, they should have completed the course in which they act as assistants and trained in lab safety procedures. Specific guidelines for training lab assistants can be found under "Student Laboratory Assistants" in Virkus (1978) pp. 51-52.
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