School Science Lessons
Laboratory safety
2009-10-10
Please send comments to: J.Elfick@uq.edu.au
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Table of contents
7.0.0
Physics laboratory safety
7.1.0
Radiation hazards
7.5.0
Laser safety
3.1.0
Workplace Health and
Safety Act,
1995, State of Queensland, Australia
3.2.0
Duties of a teacher
3.3.0 Equipment safety
3.3.1 Bunsen burner
3.4.0 Chemical safety
3.5.0 Fire safety
3.6.0
Toxicity, Metals and metal compounds
3.7.0 Hazards of anion compounds
3.8.0 Hazards associated with gases
3.9.1 Swimming pools,
checklist of daily routine for the pool
operator
3.9.2 Swimming pools, pool test ranges
18.7.0 Swimming pool chemistry
3.10.0 Toxicity, Poisons and
First aid
7.0.0 Physics laboratory
safety
7.0.1 Main points of safety consciousness
7.0.2 Safety protection in laboratory
7.0.3 General safety education
7.0.4 Necessary safety general knowledge
7.0.5 Good habits
7.0.6 Mercury
7.1.0
Radiation hazards
Radioactive substances
7.2.0 Modes of radiation exposure
7.2.1a Radiation dose from
X-rays
7.2.1b Radiation dose from
radioactive materials external to the
body
7.2.2 Radiation dose from
entry of radioactive materials into the body
7.2.3 Shielding
7.3.0 Radioactive sources
7.4.0 Cold cathode tubes, discharge tubes
7.5.0
Laser safety
7.5.1 Class 1 lasers
7.5.2 Class 2 lasers
7.5.2.1 Responsibility
7.5.2.2 Screens or shields
7.5.2.3 Warning signs
7.0.1 Main
points of safety consciousness
Ensuring the safety of the students in various activities and
experiments is the most basically responsibility of the teacher.
Remember that the students not only lack safety consciousness but also
can be
so fascinated by those interesting things that they forget safety
problems. Any activity (even a walk or having a bath) can be dangerous,
but this should not stop you organizing the students to take part
in the experiments and activities simply because of the danger. The
best way is to tell the students the specific method of avoiding
danger. It is necessary to master some techniques for those
experiments where the danger is too high for the experiment to be done
by the students themselves. When these experiments are done, they
should be shown by the teacher and the students
reminded only to observe and not to touch. All such experiments should
be done by trained teachers in advance, to find where danger
exists and to see if the students can do the experiment
themselves and to find out specific methods to avoid danger. Throughout
this book teachers are reminded to be careful. Do not forget to
consider some safety problems that are seen the most general
and often. These aspects are often neglected or missed. Things can
happen that you might not have foreseen. For example, There may be
broken or protruding objects on the wall or floor of the
laboratory. Commonly used tools may cause injury. The safety
education for students and suitable training is a good habit which is
not finished if it only done once. It is necessary to remind and
urge students often. Assessing the injury to the body should always be
done by medical professionals who have the expertise and materials to
properly treat the injury.
7.0.2 Safety protection in laboratory
There should be two doors in laboratory. The passage in front of the
doors should be always clear. Fire extinguishing materials such as a
fire blanket or carpet, a sand bucket, and a fire extinguisher
should be permanently installed in each laboratory. Laboratories should
also have first aid materials and electrical fuses or circuit breakers.
It is desirable to have earth leakage protection units installed
in the electrical supplies to laboratories if they are available. There
should be a vessel which is used to collect broken pieces of glass. Do
not place the broken glass into he garbage can. There should
not be any obstacle in laboratory passages or on the floor or in any
space where students operate which can cause safety problems. As you
prepare the equipment to be used by students, check if the
glass vessels have any cracks, the liquid leakage. All the open ends of
the glass tubes should be flame polished into a smooth shape. At
regular intervals inspect any high voltage, i.e. mains voltage,
apparatus used by students or teachers and check if the wires have been
exposed or plugs damaged. It possible this should be done by a person
qualified in electrical installation and repair. The mercury
and radioactive sources must be taken care of and operated in a fixed
place with suitable protection equipment and procedures. Government and
school authorities usually have regulations or laws in
place to cover these.
7.0.3 General safety education
Never do the experiments which are dangerous for others or yourself
except as permitted by your teachers or under the guidance of the
teachers. If you are not sure if the experiment is dangerous or not,
or beyond your knowledge, you should ask your teacher before doing it.
Do not turn on the equipment that you have never used. Do not operate
before reading the booklet of directions. Any time you
should not use the materials which are easily burned in the place where
exists fire, and you also should not do any experiment using fire near
the materials that are easily burned. Learn the positions of
the fire extinguisher, electric switch and first aid dressing in a new
experimental environment or laboratory. Learn how to use them in the
case of emergency, and master the correct method of
temporary treatment of a wound.
7.0.4 Necessary safety general knowledge
Always use safety glasses
and thick gloves when you process something that can easily burst
apart, rebound or spurt.
Do not touch the object that is moving or spinning in high
speed. Do not touch along the edge of a knife or the edge of a piece of
glass which is not rubbed smoothly. Do not clean the pieces of the
glass by your hands directly. The electricity above 30 volts
may be dangerous. The edge of screw mouth of lamp holder may be wrongly
connected as a live wire. When you do the measurement outside, don't
work under the high voltage power transmission
line. The working lamp above 10 watt and the metal just heated can burn
your hands. You may need to wear a pair of gloves to touch them. The
laser, arc light, electric welding, X-ray and ultraviolet
ray should not get into eyes. Do not look directly at a laser tube even
if it is not turned on. Do not remain exposed to ultraviolet light and
X-rays. [X-rays should not be used in schools!]
7.0.5 Good habits
Observe the surroundings around you before each experiment to avoid
unnecessary hurt to others, yourself and the equipment and facilities.
Do not touch the equipment without the permission of the
teacher at any time. Remember unexpected hazards or dangers can happen,
even with normal working. Operate equipment according to the
instruction booklet or teacher's directions. Follow the normal
method of using tools. While using tools only place your hands on the
operating handles and ensure your assistants have their hands in safe
positions. Make sure that no hands are near a cutting or hot
surface. Do not allow tools to fall from the working table. This can
damage the tool or hurt your feet or the feet of your assistants. Do
not turn on any circuit which has not been checked. (using a
multimeter to check circuits can be useful) First use the method of
turning on instantaneously (turn on, then turn off immediately). Note
to observe if the direction of the pointers on any meters is
correct and the measuring scale is suitable. After everything is
checked to be correct, you again turn on the circuit. Turn off the main
source when you find the wire or coil being over hot, a rubber
washer becoming soft, the burnt smell or overflow of the substance
which is easily burnt and hear the sound of mechanical rubbing which is
not normal. Do not turn the circuit back on before
finding the reason for the problem and fix the problem. At any time
you shouldn't examine and repair any equipment or try to find circuit
problems while the circuit is operating at a high voltage
such as the main power supplies. If you use an electric pen with a neon
tube, make sure the pen is working before using it to find the fault in
a circuit or to check for live wires. After each experiment
turn off the electric power and gas source and return the equipment and
tools to their original positions. The accessories of the meters should
be placed in the same storage position as the meters. Any
damaged equipment, even a broken wire, should be reported to the
teacher. The last person to leave the laboratory should turn off the
main source of electricity and gas.
7.0.6 Mercury
3.6.5.10 Mercury safety | 7.2.2.3 Mercury and dental amalgam
Do not use mercury in students' experiment. The mercury can evaporate
even at 0oC. Mercury vapour absorbed by the body is not
detoxified by the body and may accumulate and cause complications
with the nervous system. When mercury contacts with your skin you must
thoroughly wash the area with soap and water immediately. Mercury
should be stored in a cool ventilated place. Mercury
should be stored in an impervious container made of glass or china.
While storing mercury under water is useful, it is not sufficient.
Mercury should be stored in a sealed container. The container
should be placed in a sealed cupboard or a sealed larger container or
box. There should be some powdered sulfur or powdered zinc alongside
the mercury container to be used in case of emergency
with a mercury spill. The table used to do or examine and repair the
mercury experiment should be smooth and no slits, if there are some
slits on the table you should make them smooth and cover it
with paint. If mercury is found to be leaking or spilt in a room, the
persons in the room must go out of the room, and open all the system of
ventilation and shut the doors next to that room. The
mercury which has leaked out should be absorbed by water pump or
cleaned by wet cleaning agent. The collected mercury is put into a
sealed plastic bag or a glass bottle, then process the mercury
together with the contaminated items as you clean the mercury up.
Finally use the sulfur or zinc which can react with mercury to produce
a low vapour pressure substance which can be easily cleaned
up from the polluted region. The person who cleans the mercury up
should check very carefully that all the mercury has been cleaned up
and that none remains on the cleaning cloth.
7.1.1 Radioactive substances
Instructions for Australian Teachers
Sources of radioactivity must be put in a container made of lead with
an eye catching mark outside of the container. (The international
radiation symbol is recommended.) Use the source of
radioactivity in a special room. The persons who uses the source of
radioactivity should sign their name and time when they enter and leave
the room. Use tweezers or tongs and wear gloves when using
the source of radioactivity and wash hands thoroughly when leaving the
source of radioactivity.
The following information has been extracted from the Code of Practice
for the Safe Use of Ionizing Radiation in Secondary Schools (1986) and
the Code of Practice for the Safe Use of Lasers in
Secondary Schools (1995) produced by the National Health and Medical
Research Council. Radioactive substances generally emit alpha or beta
particles or gamma rays or combinations of these, while
X-ray units generate electromagnetic waves similar to gamma rays, but
usually of lower frequency (and longer wavelength). The amount and type
of shielding needed depends on the penetrating power
of the particular form of radiation. The denser the shielding material
the better shield it will be. Alpha particles, being charged and
relatively heavy atomic particles, are easily stopped, while gamma
rays, usually being very short waves, are far more penetrating and hard
to stop.
Alpha particles: Stopped by sheet of paper or surface layers of skin.
Beta particles: Stopped by a few millimetres of aluminium or 1-2
centimetres of plastic.
Gamma rays: Almost completely stopped by about 1 metre of concrete or
about 5 centimetres of lead. Most will pass through the human body.
X-rays (medical): Almost completely stopped by 2-3 millimetres of lead,
or about 10-15 centimetres of concrete. Will pass through the body with
some absorption depending on the density of organs in
the beam (e.g. skin, bones).
The philosophy for the control of hazards associated with the use of
ionizing radiation is as follows:
1. no practice should be adopted unless
its introduction is necessary and produces a positive net benefit,
and,
2. all exposure should be kept as low as possible.
Ionizing radiation in schools must only be used in simple experiments
to show fundamental principles. The sources used and the methods
of using them must be chosen to ensure that the degree
of hazard is negligible. Consideration should be given to minimizing
the number of experiments or demonstrations which may take place in a
year. Advice in planning such experiments or
demonstrations should be sought from: Division of Health and Medical
Physics Queensland Health Department 535 Wickham Terrace Brisbane Q
4000, Australia. Advice for packaging, transportation
and disposal of radioactive substances should be sought from: Radiation
Health 450 Gregory Terrace Fortitude Valley Q 4006, Australia. The
immediate responsibility for radiation safety in any
experiment involving radiation rests with the teacher responsible for
the class. No demonstrations or experiments requiring the exposure of
students, staff or any other person to ionizing radiation shall
be performed.
7.2.0 Modes of radiation exposure
The possible modes of radiation exposure can be divided into two
types: external or internal exposure. External irradiation
results from the exposure to X-rays or to
radiation from sealed or unsealed radioactive sources external to the
body.
7.2.1a Radiation dose
from
X-rays
The radiation dose is dependent on the following:
1. operating
factors of the X-ray tube (kV (peak) and mA),
2. duration of
irradiation,
3. protective barriers between the tube and the body,
4. distance between the tube and the body,
5. filtration of the X-rays by
material in the beam,
6. amount of scattering of the primary beam
that has taken place.
7.2.1b
Radiation dose from
radioactive materials external to the
body
The dose is dependent on the radionuclide and: 1. the type of
radiation
emitted by the radioactive materials ¾ that is, alpha particles,
beta
particles, gamma radiation or combinations of these, and the energy of
the radiation emitted 2. the activity of the radioactive substance 3.
the distance between the source and the body 4. the
protective barrier between the source and the body, and 5. the
duration of exposure to the rays. Shielding may be needed to protect
staff and students.
7.2.2
Radiation dose from
entry of radioactive materials into the body
Internal irradiation
results from the entry of radioactive
materials into the body, with the resultant exposure of organs which
have absorbed such materials and, in most cases, the exposure of other
nearby organs. The amount of radioactive materials taken into the body
depends on a variety of factors including the following:
1. the activity of the
radioactive material being handled,
2. its physical state, e.g.
liquid, gas, powder, aerosol, solid,
3. its concentration and
chemical form,
4. methods of handling and precautions taken,
5. personal hygiene,
6. the duration of handling, and,
7. site of entry
into
body, e.g. skin, wound, mouth, nose.
The radiation dose
resulting from the entry of a particular
amount of radioactive material into the body depends on the following:
1. the type
of radioactive material,
2. the type and energy of the radiation it
emits
3. its solubility, physical and chemical form, and effective
half life, and,
4. the biological behaviour (or characteristics) of the
radioactive material, e.g. some elements are selectively absorbed
by certain organs of the body, such as iodine by the thyroid, and
radium and strontium by bone.
7.2.3
Shielding
In school
experiments involving X-rays or radioactive
substances the radiation levels should be so low that no special
shielding is required. However, it is important when using
sources of radiation in schools to show the role of shielding as
part of safe working practices.
7.3.0 Radioactive sources
See 32.3.4.4: Ionization by
radioactivity, conduction
in air by ions, smoke alarms, 1.
The teacher of science must ensure that:
Only approved sealed radiation sources are used. (See page 301 of the
Code of Practice for the Safe Use of Ionizing Radiation in Secondary
Schools (1986).
All radiation sources are stored in lockable metal containers (metal
cash box is suitable) which are permanently labelled. If there is more
than one source, then they should be stored in separate
compartments within the box. This container should be kept in the
school safe.
Access to this container is limited to authorized members of the school
staff.
Sources are clearly labelled with the word radioactive, with the type
and activity of the radionuclide and, for short half life (less than 10
years) material, the year of manufacture.
Ionizing radiation sources in schools are only used for simple
experiments to show fundamental principles. The sources used and
the method of using them must ensure that the degree of hazard
is negligible.
Gifts of radioactive sources, discharge tubes, operational high voltage
generators or X-ray units of any kind are not accepted.
No demonstrations or experiments requiring the deliberate exposure of
students, staff or any other person to ionizing radiation are performed.
Routine checks of the condition of each source are carried out at
intervals not exceeding 5 years. Checks must be carried out sooner
following an event such as a fire or an accident which may have
damaged the source.
If
a source of radiation is lost, or suspected of being stolen or
damaged, the matter is reported, in the first instance, to the
principal who shall then inform the Department of Education and the
Division
of Health and Medical Physics. The immediate responsibility for
radiation safety in any experiment rests with the teacher of science
responsible for the class. The teacher should ensure that: 1. radiation
sources are only handled by tongs or forceps 2. radiation
sources are used by students only when under direct supervision 3. all
sources of radiation are accounted for 4. radiation sources
are clearly marked as radiation sources, and no person stands within
one metre of operating equipment.
7.4.0 Cold cathode tubes, discharge tubes
The following gas discharge tubes supplied to schools fall into this
category:
1. Discharge tube with side tube for connection to a vacuum
pump
2. Maltese cross discharge tube
3. Discharge tube to
illustrate the deflection of cathode rays by magnetic fields
4. Windmill tube
All these tubes are operated by high voltages produced
by induction coils and may produce unwanted X-rays incidental to
their intended use. The voltages necessary to operate these tubes
depend upon the dimensions of the tube and the pressure of the gas in
the tube. Generally, the higher the voltage used, the greater the
danger of the production of unwanted X-rays.
7.5.0 Laser safety
The following precautions must be taken when using any one of the tubes
mentioned above:
1. The voltage applied should be kept as low as
possible. The voltage from the induction coil can be varied
by changing the distance of the make-and-break hammer from the iron
core of the induction coil windings. Commence with the hammer well away
from the core and slowly decrease the distance
between them (by means of the adjusting screw) until the tube operates.
2. Such tubes shall be operated by the teacher of science for
demonstration purposes only.
3. The use of these tubes should be
limited to as short as time as possible.
4. All students should be
kept a minimum distance of one metre and teachers should also try to
observe this distance.
Do not use laser in a dark room. The direct contact of eyes and the
laser beam is forbidden. Be careful to note if the laser can hit on a
smooth surface before turning on the laser because the reflected
laser can enter other's eyes. For the same reason, do not move laser
equipment when it is working.
Instructions for Australian Teachers
The safe use of lasers for all applications is controlled by Australian
Standard AS 2211. This document, which follows international standards,
sets classifications of lasers, and documents some of the
safe practices for general applications. Guidelines for the safe use of
lasers in the classroom have been developed by the National Health and
Medical Research Council of Australia (NH and MRC) in a
Code of Practice for the safe use of Lasers in Secondary Schools
(1983). Copies of this code and further advice should be obtained from:
The Director Division of Health and Medical Physics
Department of Health 450 Gregory Terrace Brisbane Q 4000 The hazard
from lasers is primarily that of burning of tissue either in the eye
or, for high power lasers, the skin. The eye is particularly at
risk because the lens of the eye may concentrate the beam to a very
small image on the retina, in which the energy density is extremely
high. Lasers are classified according to the degree of hazard
presented. This depends on the output power, the size of the beam, the
irradiance at any point in the beam, the wavelength, and for a pulsed
laser, the power in a single pulse and the repetition
frequency. All lasers and products incorporating lasers must bear a
label stating the class of the laser product, the wavelength emitted or
the medium, and maximum power output. Devices above Class
1 must have additional safety markings. Class 1 lasers are
intrinsically safe, i.e. they cannot cause harm, either because the
exposure level which produces injury cannot be reached under any
conditions, or because engineering design is such that access to
dangerous levels is not possible. Class 2 lasers are low power devices
which emit visible radiation. They are not intrinsically safe,
although eye protection is normally afforded by aversion responses
(e.g. blinking). Classes 3A, 3B and 4 are not permitted in schools. The
supervision of the use of lasers throughout a school shall be
the responsibility of the head of department/principal. This person
shall be responsible for the buying, storage and allocation of lasers,
and for ensuring that the needs of the code are met at all
times. Only Class 1 or Class 2 lasers should be used in schools.
7.5.1 Class 1 lasers
Class 1 lasers require no special safety precautions other than to warn
students that good practice dictates that you never shine a laser beam,
regardless of its class, directly into someone's eyes.
7.5.2 Class 2 lasers
7.5.2.1 Responsibility
1. Lasers must only be used under the direct supervision of a member
of the science staff and should be used for demonstration purposes
only.
2. The teacher of science in charge of a demonstration
shall be immediately responsible for the safety of that demonstration
and the teacher shall ensure that risk assessment and management are
implemented.
3. If a new demonstration is to be introduced,
then a trial must be carried out, without students present, to evaluate
the safety aspects of the demonstration.
4. All persons must be
instructed not to look directly into the main beam or reflected or
refracted beams and students must be warned of the potential hazard and
the seriousness of eye damage.
5. Access to laser work areas should be
limited and casual observers should be excluded.
7.5.2.2 Screens or shields
1. Sunglasses and welder's goggles do not provide protection from
laser beams. Provided appropriate shields (i.e. shields complying with
the code) are used, it is not necessary for teachers or students
to wear additional protective eye wear.
2. Shields must be used to
prevent both strong reflections and the direct beam from going beyond
the area needed for demonstration. Shields must be painted
matt black to reduce reflection. The base material of such shields must
not have a shiny surface as paint may flake exposing a mirror like
surface.
3. Specularly reflected beams from shiny objects may
be hazardous even when only a small amount of the incidental beam is
reflected. Such reflections may arise from polished metal trimmings on
instrument housings and from mirrors, bottles, glass
lenses, watches, rings, cufflinks, polished wooden furniture, windows
or any smooth surface. These articles should be removed from the
vicinity of the laser or covered with matt black paper or cloth.
Care must be taken to ensure that surfaces which would otherwise
reflect diffusely do not become wet as this may cause specular
reflection.
4. Baffles should be placed near lenses, or other shiny
objects in the beam path, to intercept oblique specularly reflected
beams and oblique refracted beams. 5. The laser head must be rigidly
fixed in position so that the direction of the laser beam cannot
be accidentally altered. Optical components and shields must also be
firmly fixed in position.
6. The room lighting in the laser work area
should be as bright as practicable while the laser is in
operation, to constrict the pupil diameter of the observer's
eyes.
7.5.2.3 WARNING SIGNS
Each Class 2 laser must have attached to it a warning label with the
following dimensions: background, yellow, lettering, black, 10.5 cm x
5.2 cm, and wording.
DANGER LASER
DO NOT LOOK INTO DIRECT OR REFLECTED BEAMS
When a Class 2 laser is in operation, warning signs must be
displayed in conspicuous locations both inside and outside the
demonstration area. These signs must be removed when the laser is not
in
use. Area warning signs must conform to the following dimensions,
wording and design. Colour scheme: background, yellow, lettering,
black. Minimum dimensions: 20 cm edge triangle:
DANGER LASER
LASER OPERATING IN THIS AREA