Connecticut Middle School Science Safety

6. Physical Science Laboratory Safety Specifications

In this section

Physics-Based Physical Science

Chemistry-Based Physical Science

Earth/Space Science-Based Physical Science

Physical science includes the sciences of earth/space science, chemistry and physics that explore the nature and characteristics of energy and nonliving matter. The boundaries between the physical and life sciences are artificial. With the advancements in science today, one field overlaps into another; e.g., biophysics, biochemistry, etc.

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Physics-Based Physical Science

A. Electricity

Given the inherent dangers in the laboratory study of electricity, safeguards and safety procedures need to be in place for students and teachers. Consider the following safety specifications in working with electricity:

  1. Know where the master switch is for electricity in the laboratory in case of an emergency.
  2. Make students aware of the appropriate use of electricity and dangers of misuse and abuse.
  3. When using batteries, always inspect them first for damage including cracks, leakage. Discard in an environmentally appropriate way if any of these conditions occur.
  4. When unplugging cords, always pull cords from the plug at the electrical receptacle and never pull the cords from the wire.
  5. Use only ground fault interrupt circuits (GFI) protected circuits!
  6. Remove all conductive or metallic jewelry before working with electricity.
  7. Prevent trip and fall hazards by placing wires away from places where people walk.
  8. For routine maintenance like changing bulbs, make sure the device is unplugged before initiating the work.
  9. Never open a battery. The contents are corrosive and can be toxic or poisonous.
  10. When storing batteries, never allow the terminals to touch or short circuit.
  11. Be water phobic when working around electricity. Never use water or have wet hands when dealing with cords, plugs or electrical equipment. Never run a cord near or over a sink.
  12. Utility pipes such as water and gas are grounded. Do not touch an electrical circuit and utility pipes at the same time.
  13. Never plug damaged electrical equipment into a wall receptacle. This includes frayed wires, missing ground pin and bent plugs.
  14. Never overload circuits as they will overheat and cause power outages or fires.

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B. Electrostatic Generators:

Electrostatic generators such as Van de Graaff generators are a real attention getter for students in the study of electrostatics. The following prudent safety procedures are in order, however:

  1. The generator should only be operated as a demonstration by the teacher.
  2. Electronic circuit or devices such as cell phones, computers and cameras can be permanently damaged by the machine's sparks. Keep them at least 50 feet (12 meters) away.
  3. Always use a surge protector inline with the generator's power cord.
  4. Students with epilepsy, heart or nervous system conditions, or pacemakers should never be in the proximity of an electrostatic generator.
  5. Never operate the generator near flammable or combustible materials.
  6. Never leave the machine operating unattended.

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C. Ionizing Radiation:

The use of ionizing radiation sources in middle school science laboratories is not advocated given the potential for unsafe exposure levels and health indication.

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D. Mechanics:

The study of mechanics in physical science provides many touchstones to everyday applications for students. However, laboratory activities in this area are not without safety concerns. Students and teachers can be injured if hit by rapidly moving objects or projectiles.

Always use caution when dealing with projectiles, falling objects, moving equipment, exposed belts, powerful permanent magnets, sharps such as Exacto knives and razor blades, and springs.

Special attention should be given to the following safety procedures when working with model rockets.

Use only lightweight, nonmetal parts for the nose, body and fins of the rocket.

  1. Use only commercially made model rocket engines.
  2. To prevent accidental eye injury, place launchers so that the end of the launch rod is above eye level or cap the end of the rod when it is not in use.
  3. Always use either safety glasses or safety goggles with an ANSI Z-1 rating when launching rockets.
  4. Do not tamper with rocket engines or use them for any purposes except those recommended by the manufacturer.
  5. Launch rockets outdoors, in an open area and in safe weather conditions with wind speeds no greater than 20 mph.
  6. Use a recovery system such as a flame-resistant or fireproof streamer or parachute so that it returns safely and undamaged and can be flown again.
  7. Launch rockets with an electrical launch system and electrical motor igniters.
  8. The launch system should have a safety interlock in series with the launch switch, and will use a launch switch that returns to the "off" position when released.
  9. Use a safe launch distance of at least 15 feet (6 meters) away from the launch pad for rockets with up to "D" size engines. Use 30 feet (1 meters) when launching larger rockets engines.
  10. If the rocket misfires, remove the launcher's safety interlock or disconnect its battery. Wait 60 seconds after the last launch attempt before allowing anyone near the rocket.
  11. Launch a rocket from a launch rod, tower, or rail that is pointed within 30 degrees of the vertical to ensure the rocket flies nearly straight up.
  12. Use a blast deflector to prevent the engine's exhaust from hitting the ground.
  13. Do not launch rockets at targets such as tall buildings, power lines or near airplanes.
  14. Never put any flammable or explosive payload in a rocket.
  15. Do not attempt to recover rockets from power lines, tall trees or other dangerous places.

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E. Nonionizing Radiation – Lasers:

Nonionizing radiation consists of electromagnetic radiation that lacks sufficient energy to ionize matter. These may include the use of lasers, microwaves and infrared radiation in the physical science laboratory. Nonionizing radiation can cause injury if handled improperly.

It is prudent safety practice to have students and teachers wear ultraviolet-protected chemical splash goggles when working with ultraviolet light sources. Students' skin and eyes can be particularly sensitive to ultraviolet exposure. When using hand-held ultraviolet lamps for activities such as forensics or phosphoresce, use caution not to directly view the ultraviolet light source.

The most common nonionizing radiation equipment used in physical science laboratories is the laser. Safety specifications vary depending on the class of laser instrument being used. The following general safety specifications provide prudent advice and direction for use in middle school physical science courses:

  1. Lasers, including handheld laser pointers, should be used only for demonstration purposes by the teacher. Connecticut has the following general statute relative to laser pointers:

    Connecticut General Statutes (C.G.S.)

    § 53-206e. Limitation on sale and use of laser pointers

    (a) As used in this section, "laser pointer" means a hand-held device that emits a laser light beam and is designed to be used by the operator to indicate, mark or identify a specific position, place, item or object.

    (b) No person shall sell, offer to sell, lease, give or otherwise provide a laser pointer to a person under eighteen years of age, except as provided in subsection (d) of this section.

    No person under eighteen years of age shall possess a laser pointer on school grounds or in any public place, except as provided in subsection (d) of this section.

    (d) A person may temporarily transfer a laser pointer to a person under eighteen years of age for an educational or other lawful purpose provided the person to whom the laser pointer is temporarily transferred is under the direct supervision of a parent, legal guardian, teacher, employer or other responsible adult.

    (e) No person shall shine, point or focus a laser pointer, directly or indirectly, upon or at another person in a manner that can reasonably be expected to cause harassment, annoyance or fear of injury to such other person.

    (f) Any person who violates any provision of this section shall have committed an infraction.

  2. Before operation, warn all individuals present of the potential hazard.
  3. Use the laser away from areas where the uninformed and curious might be attracted by its operation.
  4. In conspicuous locations inside and outside the work area and on doors giving access to the area, place hazardous warning signs indicating that a laser is in operation and may be hazardous.
  5. Remove all watches and rings before changing or altering the experimental setup. Shiny jewelry can cause hazardous reflections.
  6. Practice good housekeeping in the lab to ensure that no device, tool or other reflective material is left in the path of the beam.
  7. Cover all exposed wiring and glass on the laser with a shield to prevent shock and contain any explosions of the laser materials. Be sure all nonenergized parts of the equipment are grounded.
  8. Set up the laser so that the beam path is not at normal eye level, i.e., below 3 feet (9 meters) or above 5 feet (2 meters).
  9. Use shields to prevent strong reflections and the direct beam from going beyond the area needed for the demonstration or experiments.
  10. Use only lasers operating inside the visible range.
  11. A key switch to lock the high voltage supply should be installed.
  12. View holograms only with a diverged laser beam. Be sure the diverging lens is firmly attached to the laser.
  13. Illuminate the area as brightly as possible to constrict the pupils of the observers.
  14. The target of the beam should be a diffuse material capable of absorbing the beam and reflection
  15. Do not at any time look into the primary beam of a laser.
  16. Do not aim the laser with the eye. Direct reflection can cause eye damage.
  17. Do not look at reflections of the beam. These, too, can cause retinal burns.
  18. Do not use sunglasses to protect the eyes. If laser safety goggles are used, be certain they are designed for use with the laser being used.
  19. Report any afterimage to a doctor, preferably an ophthalmologist who has had experience with retinal burns. Retinal damage is possible.
  20. Do not leave a laser unattended.

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F. Pressurized and Vacuum Systems:

Pressurized gas cylinders can explode. Bell jars can implode. Use only pressurized or evacuated items that are designed for such an activity.

Working with vacuums has the potential of an implosion and the possible hazards of flying glass, splattering chemicals and fire. Potential risks must be carefully considered. Equipment at reduced pressure can be prone to rapid pressure changes forcing liquids through an apparatus.

For safety prevention, adopt the following safety protocols when dealing with pressurized and vacuum systems:

  1. Always use safety glasses or goggles with ANSI Z81 ratings.
  2. Procedures should always be effected inside a hood.
  3. Place vacuum apparatus out of harm's way so an accidental hit is minimized. Placement of transparent plastic around the apparatus helps prevent injury from flying glass in case of an explosion.
  4. Protect vacuum pumps with cold traps and vent the exhaust into an exhaust hood.
  5. Assemble vacuum apparatus in a manner that avoids strain, particularly to the neck of the flask.
  6. Do not allow water, solvents and corrosive gases to be drawn into vacuum systems.
  7. Avoid putting pressure on a vacuum line to prevent stopcocks from popping out or glass apparatus from exploding.

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G. Sound:

Usually physical science laboratory equipment and activities do not normally produce noise levels requiring use of hearing protection. The OSHA Occupational Noise Standard (29 CFR 1910.95) has established a noise action level of 85 decibels (dBA) averaged over eight hours. Wind tunnels, motors, engines and other laboratory equipment used in physical science laboratories have the potential to exceed the action level. Science teachers should monitor sound levels and provide hearing protection for themselves and students. It is advised that this be applied even below the action level.

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Chemistry-Based Physical Science

A. Hazard Communication Standard (HCS) to conform with the United Nations' (UN) Globally Harmonized System of Classification and Labeling of Chemicals (GHS)

The Globally Harmonized System (GHS) is an international approach to hazard communication, providing agreed criteria for classification of chemical hazards, and a standardized approach to label elements and safety data sheets. The GHS was negotiated in a multi-year process by hazard communication experts from many different countries, international organizations, and stakeholder groups. It is based on major existing systems around the world, including OSHA's Hazard Communication Standard and the chemical classification and labeling systems of other US agencies.

The result of this negotiation process is the United Nations' document entitled "Globally Harmonized System of Classification and Labeling of Chemicals," commonly referred to as The Purple Book. This document provides harmonized classification criteria for health, physical, and environmental hazards of chemicals. It also includes standardized label elements that are assigned to these hazard classes and categories, and provide the appropriate signal words, pictograms, and hazard and precautionary statements to convey the hazards to users. A standardized order of information for safety data sheets is also provided. These recommendations can be used by regulatory authorities such as OSHA to establish mandatory requirements for hazard communication, but do not constitute a model regulation. For additional information, go to the list of frequently asked questions.

The three major areas of change are in hazard classification, labels, and safety data sheets.

  • Hazard classification: The definitions of hazard have been changed to provide specific criteria for classification of health and physical hazards, as well as classification of mixtures. These specific criteria will help to ensure that evaluations of hazardous effects are consistent across manufacturers, and that labels and safety data sheets are more accurate as a result.
  • Labels: Chemical manufacturers and importers will be required to provide a label that includes a harmonized signal word, pictogram, and hazard statement for each hazard class and category. Precautionary statements must also be provided.
  • Safety Data Sheets: Will now have a specified 16-section format.

The table below summarizes the phase-in dates required under the revised Hazard Communication Standard (HCS):

Hazardous Communication Standard Phase-in Dates

Effective Completion Date



December 1, 2013

Train employees on the new label elements and safety data sheet (SDS) format.


June 1, 2015*
December 1, 2015

Compliance with all modified provisions of this final rule, except:
The Distributor shall not ship containers labeled by the chemical manufacturer or importer unless it is a GHS label

Chemical manufacturers, importers, distributors and employers

June 1, 2016

Update alternative workplace labeling and hazard communication program as necessary, and provide additional employee training for newly identified physical or health hazards.


Transition Period to the effective completion dates noted above

May comply with either 29 CFR 1910.1200 (the final standard), or the current standard, or both

Chemical manufacturers, importers, distributors, and employers

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B. Hazard Classifications:

(The following information is from A Guide to The Globally Harmonized System of Classification and Labelling of Chemicals (GHS)

Classification is the starting point for hazard communication. It involves the identification of the hazard(s) of a chemical or mixture by assigning a category of hazard/danger using defined criteria. The GHS is designed to be consistent and transparent. It draws a clear distinction between classes and categories in order to allow for "self classification." For many hazards a decision tree approach (e.g., eye irritation) is provided in the GHS Document. For several hazards the GHS criteria are semi-quantitative or qualitative. Expert judgment may be required to interpret these data.

Figure 3.1 Hazard Classification

The term "hazard classification is used to indicate that only the intrinsic hazardous properties of substances and mixtures are considered and involves the following 3 steps:

a) Identification of relevant data regarding the hazards of a substance or mixture;

b) Subsequent review of those data to ascertain the hazards associated with the substance or mixture; and

c) A decision on whether the substance or mixture will be classified as a hazardous substance or mixture and the degree of hazard, where appropriate, by comparison of the data with agreed hazard classification criteria.

Figure 3.1 shows the harmonized definition for hazard classification, which can be applied to all hazard categories in the system.

The data used for classification may be obtained from tests, literature, and practical experience. The GHS health and environmental hazard criteria/definitions are test method neutral. Accordingly, tests that determine hazardous properties conducted according to internationally recognized scientific principles can be used for purposes of hazard classification.

The GHS endpoints that cover physical, health and environmental hazards are listed in Figures 3.2 and 3.3, respectively. As mentioned earlier, the GHS hazard definitions are criteria-based. The following information provides an overview of the GHS definitions and classification criteria. It is recommended that the person responsible for GHS implementation consult the GHS Document or "Purple Book" for more complete information.

3.1 What are the GHS Physical Hazards?

The GHS physical hazards criteria, developed by the ILO and UNCETDG, were largely based on the existing criteria used by the UN Model Regulation on the Transport of Dangerous Goods. Therefore, many of the criteria are already being used on a worldwide basis. However, some additions and changes were necessary since the scope of the GHS includes all target audiences. The physical hazards classification process provides specific references to approved test methods and criteria for classification. The GHS physical hazard criteria apply to mixtures. It is assumed that mixtures will be tested for physical hazards.

In general, the GHS criteria for physical hazards are quantitative or semi-quantitative with multiple hazard levels within an endpoint. This is different from several of the existing systems that currently have qualitative criteria for various physical hazards (e.g., organic peroxide criteria under WHMIS and OSHA HCS). This could make classification under the GHS more consistent.

In developing GHS criteria for physical hazards it was necessary to define physical states. In the GHS,

  • gas is a substance or mixture which at 50°C has a vapor pressure greater than 300 kPa; or is completely gaseous at 20°C and a standard pressure of 101.3 kPa.
  • liquid is a substance or mixture that is not a gas and which has a melting point or initial melting point of 20°C or less at standard pressure of 101.3 kPa.
  • solid is a substance or mixture that does not meet the definitions of a liquid or a gas.

The GHS physical hazards are briefly described below. For many of the physical hazards the GHS Document contains Guidance Sections with practical information to assist in applying the criteria.

Figure 3.2 Physical Hazard

  • Explosives
  • Flammable Gases
  • Flammable Aerosols
  • Oxidizing Gases
  • Gases Under Pressure
  • Flammable Liquids
  • Flammable Solids
  • Self-Reactive Substances
  • Pyrophoric Liquids
  • Pyrophoric Solids
  • Self-Heating Substances
  • Substances which, in contact with water emit flammable gases
  • Oxidizing Liquids
  • Oxidizing Solids
  • Organic Peroxides
  • Corrosive to Metals

3.1.1 Explosives

An explosive substance (or mixture) is a solid or liquid which is in itself capable by chemical reaction of producing gas at such a temperature and pressure and at such a speed as to cause damage to the surroundings. Pyrotechnic substances are included even when they do not evolve gases. A pyrotechnic substance (or mixture) is designed to produce an effect by heat, light, sound, gas or smoke or a combination of these as the result of non-detonative, self-sustaining, exothermic chemical reactions.

Classification as an explosive and allocation to a division is a three-step process:

  • Ascertain if the material has explosive effects (Test Series 1);
  • Acceptance procedure (Test Series 2 to 4);
  • Assignment to one of six hazard divisions (Test Series 5 to 7).

Table 3.1 Explosives




Mass explosion hazard


Projection hazard


Fire hazard or minor projection hazard


No significant hazard


Very insensitive substances with mass explosion hazard


Extremely insensitive articles with no mass explosion hazard

Explosive properties are associated with certain chemical groups that can react to give very rapid increases in temperature or pressure. The GHS provides a screening procedure that is aimed at identifying the presence of such reactive groups and the potential for rapid energy release. If the screening procedure identifies the substance or mixture to be a potential explosive, the acceptance procedure has to be performed.

Substances, mixtures and articles are assigned to one of six divisions, 1.1 to 1.6, depending on the type of hazard they present. See, UN Manual of Tests and Criteria Part I Test Series 2 to 7. Currently, only the transport sector uses six categories for explosives.

3.1.2 Flammable Gases

Flammable gas means a gas having a flammable range in air at 20°C and a standard pressure of 101.3 kPa. Substances and mixtures of this hazard class are assigned to one of two hazard categories on the basis of the outcome of the test or calculation method (ISO 10156:1996).

3.1.3 Flammable Aerosols

Aerosols are any gas compressed, liquefied or dissolved under pressure within a non-refillable container made of metal, glass or plastic, with or without a liquid, paste or powder. The container is fitted with a release device allowing the contents to be ejected as solid or liquid particles in suspension in a gas, as a foam, paste or powder or in a liquid or gaseous state.

Aerosols should be considered for classification as either a Category 1 or Category 2 Flammable Aerosol if they contain any component classified as flammable according to the GHS criteria for flammable liquids, flammable gases, or flammable solids. Classification is based on:

  • Concentration of flammable components;
  • Chemical heat of combustion (mainly for transport/storage);
  • Results from the foam test (foam aerosols) (mainly for worker/consumer);
  • Ignition distance test (spray aerosols) (mainly for worker/consumer);
  • Enclosed space test (spray aerosols) (mainly for worker/consumer).

Aerosols are considered:

  • Nonflammable, if the concentration of the flammable components  1% and the heat of combustion is less than 20 kJ/g
  • Extremely flammable, if the concentration of the flammable components >85% and the heat of combustion is > 30 kJ/g to avoid excessive testing.

See the UN Manual of Tests and Criteria for the test method.

3.1.4 Oxidizing Gases

Oxidizing gas means any gas which may, generally by providing oxygen, cause or contribute to the combustion of other material more than air does. Substances and mixtures of this hazard class are assigned to a single hazard category on the basis that, generally by providing oxygen, they cause or contribute to the combustion of other material more than air does. The test method is ISO 10156:1996. Currently, several workplace hazard communication systems cover oxidizers (solids, liquids, gases) as a class of chemicals.

3.1.5 Gases under Pressure

Gases under pressure are gases that are contained in a receptacle at a pressure not less than 280 Pa at 20°C or as a refrigerated liquid. This endpoint covers four types of gases or gaseous mixtures to address the effects of sudden release of pressure or freezing which may lead to serious damage to people, property, or the environment independent of other hazards the gases may pose.

For this group of gases, the following information is required:

  • vapor pressure at 50°C;
  • physical state at 20°C at standard ambient pressure;
  • critical temperature.

Criteria that use the physical state or compressed gases will be a different classification basis for some workplace systems.

Table 3.2 Gases under Pressure



Compressed gas

Entirely gaseous at -50°C

Liquefied gas

Partially liquid at temperatures > -50°C

Refrigerated liquefied gas

Partially liquid because of its low temperature

Dissolved gas

Dissolved in a liquid phase solvent

Data can be found in the literature, and calculated or determined by testing. Most pure gases are already classified in the UN Model Regulations. Gases are classified, according to their physical state when packaged, into one of four groups as shown in Table 3.2.

3.1.6 Flammable Liquids

Flammable liquid means a liquid having a flash point of not more than 93°C. Substances and mixtures of this hazard class are assigned to one of four hazard categories on the basis of the flash point and boiling point (See Table 3.3). Flash Point is determined by closed cup methods as provided in the GHS document, Chapter 2.5, paragraph 11.

Table 3.3 Flammable Liquids

 Category Criteria
1 Flash point less than 23°C and initial boiling point equals 35°C (95°F)
 2 Flash point less than 23°C and initial boiling greater than 35°C (95°F)
 3 Flash point = 23°C and = 60°C (140°F)
 4  Flash point = 60°C (140F) and = 93°C (200°F)

3.1.7 Flammable Solids

Flammable solids are solids that are readily combustible, or may cause or contribute to fire through friction. Readily combustible solids are powdered, granular, or pasty substances which are dangerous if they can be easily ignited by brief contact with an ignition source, such as a burning match, and if the flame spreads rapidly.

Substances and mixtures of this hazard class are assigned to one of two hazard categories (Table 3.4) on the basis of the outcome of the UN Test N.1 (UN Manual of Tests and Criteria). The tests include burning time, burning rate and behavior of fire in a wetted zone of the test sample.

Table 3.4 Flammable Solids




Metal Powders: burning time = 5 minutes

Others: wetted zone does not stop fire & burning time less than 45 seconds or burning greater than 2.2 mm/second


Metal Powders: burning time > 5 and = 10 minutes

Others: wetted zone stop fire for at least 4 minutes & burning time less than 45 seconds or burning rate greater than 2.2mm/second

3.1.8 Self-Reactive Substances

Self-reactive substances are thermally unstable liquids or solids liable to undergo a strongly exothermic thermal decomposition even without participation of oxygen (air). This definition excludes materials classified under the GHS as explosive, organic peroxides or as oxidizing. These materials may have similar properties, but such hazards are addressed in their specific endpoints. There are exceptions to the self-reactive classification for material: (i) with heat of decomposition  less thank 300 J/g or (ii) with self-accelerating decomposition temperature (SADT) greater than 75°C for a 50 kg package.

Substances and mixtures of this hazard class are assigned to one of the seven 'Types', A to G, on the basis of the outcome of the UN Test Series A to H (UN Manual of Tests and Criteria). Currently, only the transport sector uses seven categories for self-reactive substances (Table 3.5).

Table 3.5 Self-Reactive Substances




Can detonate or deflagrate rapidly, as packaged.


Possess explosive properties and which, as packaged, neither detonates nor deflagrates, but is liable to undergo a thermal explosion in that package.


Possess explosive properties when the substance or mixture as package cannot detonate or deflagrate rapidly or undergo a thermal explosion.


  • Detonates partially, does not deflagrate rapidly and shows no violent effect when heated under confinement; or
  • Does not detonate at all, deflagrates slowly and shows no violent effect when heated under confinement; or
  • Does not detonate or deflagrate at all and shows a medium effect when heated under confinement.


Neither detonates nor deflagrates at all and shows low or no effect when heated under confinement.


Neither detonates in the cavitated bubble state nor deflagrates at all and shows only a low or no effect when heated under confinement as well as low or no explosive power.


Neither detonates in the cavitated state nor deflagrates at all and shows non effect when heated under confinement nor any explosive power, provided that it is thermally stable (self-accelerating decomposition temperature is 60°C to 75°C for a 50 kg package), and, for liquid mixtures, a diluent having a boiling point not less than 150°C is used for desensitization.

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3.1.9 Pyrophoric Liquids

A pyrophoric liquid is a liquid which, even in small quantities, is liable to ignite within five minutes after coming into contact with air. Substances and mixtures of this hazard class are assigned to a single hazard category on the basis of the outcome of the UN Test N.3 (UN Manual of Tests and Criteria).

3.1.10 Pyrophoric Solids

A pyrophoric solid is a solid which, even in small quantities, is liable to ignite within five minutes after coming into contact with air. Substances and mixtures of this hazard class are assigned to a single hazard category on the basis of the outcome of the UN Test N.2 (UN Manual of Tests and Criteria).

3.1.11 Self-Heating Substances

A self-heating substance is a solid or liquid, other than a pyrophoric substance, which, by reaction with air and without energy supply, is liable to self-heat. This endpoint differs from a pyrophoric substance in that it will ignite only when in large amounts (kilograms) and after long periods of time (hours or days). Substances and mixtures of this hazard class are assigned to one of two hazard categories on the basis of the outcome of the UN Test N.4 (UN Manual of Tests and Criteria).

3.1.12 Substances which on Contact with Water Emit Flammable Gases

Substances that, in contact with water, emit flammable gases are solids or liquids which, by interaction with water, are liable to become spontaneously flammable or to give off flammable gases in dangerous quantities. Substances and mixtures of this hazard class are assigned to one of three hazard categories on the basis of test results (UN Test N.5 UN Manual of Tests and Criteria), which measure gas evolution and speed of evolution.

Table 3.6 Substances which on Contact with Water Emit Flammable Gases




=10 L/kg/1 minute


=20 L/kg/ 1 hour + less than 10 L/kg/1 min


=1 L/kg/1 hour + less than 20 L/kg/1 hour

Not classified

less than 1 L/kg/1 hour

3.1.13 Oxidizing Liquids

An oxidizing liquid is a liquid which, while in itself not necessarily combustible, may, generally by yielding oxygen, cause or contribute to the combustion of other material. Substances and mixtures of this hazard class are assigned to one of three hazard categories on the basis of test results (UN Test O.2 UN Manual of Tests and Criteria) which measure ignition or pressure rise time compared to defined mixtures.

3.1.14 Oxidizing Solids

An oxidizing solid is a solid which, while in itself not necessarily combustible, may, generally by yielding oxygen, cause or contribute to the combustion of other material. Substances and mixtures of this hazard class are assigned to one of three hazard categories on the basis of test results (UN Test O.1 UN Manual of Tests and Criteria) which measure mean burning time and re compared to defined mixtures. Currently, several workplace hazard communication systems cover oxidizers (solids, liquids, gases) as a class of chemicals.

3.1.15 Organic Peroxides

An organic peroxide is an organic liquid or solid which contains the bivalent -0-0- structure and may be considered a derivative of hydrogen peroxide, where one or both of the hydrogen atoms have been replaced by organic radicals. The term also includes organic peroxide formulations (mixtures). Such substances and mixtures may:

  • be liable to explosive decomposition;
  • burn rapidly;
  • be sensitive to impact or friction;
  • react dangerously with other substances.

Substances and mixtures of this hazard class are assigned to one of seven 'Types', A to G, on the basis of the outcome of the UN Test Series A to H (UN Manual of Tests and Criteria). Currently, only the transport sector uses seven categories for organic peroxides.

Table 3.7 Organic Peroxides




Can detonate or deflagrate rapidly, as packaged.


Possess explosive properties and which, as packaged, neither detonates nor deflagrates rapidly, but is liable to undergo a thermal explosion in that package.


Possess explosive properties when the substance or mixture as packaged cannot detonate or deflagrate rapidly or undergo a thermal explosion.


  • Detonates partially, does not deflagrate rapidly and shows no violent effect when heated under confinement; or
  • Does not detonate at all, deflagrates slowly and shows no violent effect when heated under confinement; or
  • Does not detonate or deflagrate at all and shows a medium effect when heated under confinement.


Neither detonates nor deflagrates at all and shows low or no effect when heated under confinement.


Neither detonates in the caviated bubble state nor deflagrates at all and shows only a low or no effect when heated under confinements as well as low or nonexplosive power.


Neither detonates in the caviated state nor deflagrates at all and shows no effect when heated under confinement nor any explosive power, provided that it is thermally stable (self-accelerating decomposition temperature is 60°C to 75°C for a 50 kg package), and, for liquid mixtures, a diluent having a boiling point not less than 150°C is used for desensitization.

3.1.16 Substances Corrosive to Metal

A substance or a mixture that by chemical action will materially damage, or even destroy, metals is termed 'corrosive to metal'. These substances or mixtures are classified in a single hazard category on the basis of tests (Steel: ISO 9328 (II): 1991 - Steel type P235; Aluminum: ASTM G31-72 (1990) - non-clad types 7075-T6 or AZ5GU-T66). The GHS criteria are a corrosion rate on steel or aluminum surfaces exceeding 6.25 mm per year at a test temperature of 55°C.

The concern in this case is the protection of metal equipment or installations in case of leakage (e.g., plane, ship, tank), not material compatibility between the container/tank and the product. This hazard is not currently covered in all systems.

3.2 What are the GHS Health and Environmental Hazards?

The GHS health and environmental hazard criteria represent a harmonized approach for existing classification systems (see Figure 3.3). The work at the OECD to develop the GHS criteria included:

  • A thorough analysis of existing classification systems, including the scientific basis for a system and its criteria, its rationale and an explanation of the mode of use;
  • A proposal for harmonized criteria for each category. For some categories the harmonized approach was easy to develop because the existing systems had similar approaches. In cases where the approach was different, a compromise consensus proposal was developed.
  • Health and environmental criteria were established for substances and mixtures.

Figure 3.3

Health Hazard

  • Acute Toxicity
  • Skin Corrosion/Irritation
  • Serious Eye Damage/Eye Irritation
  • Respiratory or Skin Sensitization
  • Germ Cell Mutagenicity
  • Carcinogenicity
  • Reproductive Toxicology
  • Target Organ Systemic Toxicity - Single Exposure
  • Target Organ Systemic Toxicity - Repeated Exposure
  • Aspiration Toxicity


Environmental Hazard

  • Hazardous to the Aquatic Environment
    • Acute aquatic toxicity
    • Chronic aquatic toxicity
    • Bioaccumulation potential
    • Rapid degradability

For additional information, check out OSHA's Web site.

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C. Ordering Chemicals – Safety Procedures:

With the cost of shipping, storing and disposing of chemicals, planning for ordering of chemicals is critical. The following safety procedures are recommended for ordering practices:

  1. Estimate the amount of chemicals needed based on inventory.
  2. Order only minimal amounts of chemicals. Think "micro-chemistry"!
  3. Review SDS for all new chemicals.
  4. Make sure laboratory ventilation system and/or fume hood exhaust will meet the needs for chemical use.
  5. Make sure appropriate storage is available: flammable liquid cabinet, acid cabinet, chemical storeroom.

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D. Receiving Chemicals:

Safety procedures for receiving shipments of chemicals and their use include the following:

  1. Purchase orders should have SDS requirements stated for all hazardous chemicals purchased.
  2. Make sure chemicals are stable and secure for transporting.
  3. Only transport chemicals with minimum exposure to building occupants.
  4. Gas cylinders should normally not be stored or used at the middle school level science laboratory.
  5. Do not accept any hazardous chemicals without an SDS.
  6. Do not accept any hazardous chemicals without proper labeling.

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E. Storage of Chemicals:

  1. All chemical shelving needs front edge lips of approximately 0.75-inches (9 centimeters) in height.
  2. All chemical storage areas are considered secured areas and must have locks. Only science certified personnel, administrators or trained custodians should have access. Students are not to have access to any chemical storage areas.
  3. Storage areas are to have appropriate ventilation (non-re-circulating) with a minimum of four room changes per hour.
  4. All chemical storage shelving and cabinets are to be secured to the wall to prevent tipping over.
  5. Chemicals should not be stored above eye level.
  6. Have a spill control station near the chemical storage site.
  7. All chemicals containers must be properly labeled, dated and in good condition in preparation for storage.
  8. Chemicals are to be organized by compatibility, not alphabetically. Incompatible chemicals are to be stored separately.
  9. Chemicals should be stored alphabetically within compatible groups.
  10. Segregate chemicals by hazard class (e.g., flammable liquids, combustible liquids, flammable solids, corrosive acids, corrosive bases, oxidizers and water reactives).
  11. Flammable liquids should be stored in National Fire Protection Association (NFPA) approved safety cans and cabinets.
  12. Hazardous liquids should be stored within a secondary containment.
  13. Chemicals should not be exposed to direct heat, sunlight or highly variable temperatures.
  14. Never place large or heavy containers on high shelves.
  15. Never store chemicals on tops of cabinets or on floors.

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F. Handling and Using Chemicals:

  1. Be aware of safety equipment location in case of a chemical splash or spill including the chemical spill cart.
  2. Review SDS and labels for hazards associated with a chemical before using it.
  3. Do not eat or drink in the laboratory.
  4. Use the buddy system. Never work alone without another staff member present.
  5. Use appropriate personal protective equipment (PPE): chemical splash goggles, hand protections, apron, closed toed shoes. Flip flops and sandals are inappropriate footwear in the chemistry lab.
  6. Never smell, taste or touch chemicals with bare hands.
  7. Never return a chemical to original container once it has been removed.
  8. Never leave hazardous chemicals or processes unattended.
  9. Use good housekeeping practices. Keep areas clean and uncluttered.
  10. Always clean up after completing the laboratory activity.
  11. Always wash hands with soap and water after completing the laboratory activity.

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G. Chemical Disposal:

  1. Chemicals are to be disposed of or recycled using environmentally safe procedures.
  2. Read SDS for appropriate chemical disposal.
  3. Place used chemicals or products in containers designed and labeled for that purpose
  4. Label the container with appropriate chemical information – content and volume or mass.
  5. Keep container closed unless filling.
  6. Contact the school's facility department for appropriate disposal instructions.
  7. Use only certified and approved chemical waste contractors.

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H. Chemical Labeling-National Fire Protection Association (NFPA) System:

The NFPA system of chemical labeling is characterized by a color coded diamond shaped symbol. It is designed to quickly identify safety hazards of the material and the degree of flammability, level of health and instability hazards. For a detailed explanation, visit the following Web sites:

The NFPA's Hazard Rating Diamond

NFPA 704 Hazard Rating System

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I. Chemical Labeling:

Under the revised HCS, once the hazard classification is completed, the standard specifies what information is to be provided for each hazard class and category. Labels will require the following elements:

  • Pictogram: a symbol plus other graphic elements, such as a border, background pattern, or color that is intended to convey specific information about the hazards of a chemical. Each pictogram consists of a different symbol on a white background within a red square frame set on a point (i.e. a red diamond). There are nine pictograms under the GHS. However, only eight pictograms are required under the HCS.
  • Signal words: a single word used to indicate the relative level of severity of hazard and alert the reader to a potential hazard on the label. The signal words used are "danger" and "warning." "Danger" is used for the more severe hazards, while "warning" is used for less severe hazards.
  • Hazard Statement: a statement assigned to a hazard class and category that describes the nature of the hazard(s) of a chemical, including, where appropriate, the degree of hazard.
  • Precautionary Statement: a phrase that describes recommended measures to be taken to minimize or prevent adverse effects resulting from exposure to a hazardous chemical, or improper storage or handling of a hazardous chemical.

There are nine pictograms under the GHS to convey the health, physical and environmental hazards. The final Hazard Communication Standard (HCS) requires eight of these pictograms, the exception being the environmental pictogram, as environmental hazards are not within OSHA's jurisdiction. The hazard pictograms and their corresponding hazards are shown below.

Health Hazard


Exclamation Mark

 Health Hazard
  • Carcinogen
  • Mutagenicity
  • Reproductive Toxicity
  • Respiratory Sensitizer
  • Target Organ Toxicity
  • Aspiration Toxicity
  • Flammables
  • Pyrophorics
  • Self-Heating
  • Emits Flammable Gas
  • Self-Reactives
  • Organic Peroxides
 Exclamation mark
  • Irritant (skin and eye)
  • Skin Sensitizer
  • Acute Toxicity (harmful)
  • Narcotic Effects
  • Respiratory Tract Irritant
  • Hazardous to Ozone Layer
 Gas Cylinder Corrosion Exploding Bomb

Gas cylinder

  • Gases under Pressure


  • Skin Corrosion/ burns
  • Eye Damage
  • Corrosive to Metals

Exploding bomb

  • Explosives
  • Self-Reactives
  • Organic Peroxides
Flame over Circle Environment Skull and Crossbones

Flame over circle

  • Oxidizers



  • Aquatic Toxicity

Skull and crossbones

  • Acute Toxicity (fatal or toxic)


For additional information, go to OSHA's Web site.

Hazardous Materials Identification System HMIS Hazardous Materials Identification System (HMIS) was developed by the National Paint & Coatings Association (NPCA) in concert with OSHA’s HazCom Standard. It allows employees to quickly know the type and degree of hazards associated with the chemical being used. However, it is not designed for emergency information like the NFPA system.

See the MSDS HyperGlossary and the American Coatings Association.

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J. Secondary Labels:

If chemicals are transferred from a stock bottle into a smaller container, the latter is known as a secondary container. Although OSHA does not require labeling of the secondary container in all instances (e.g., one person filling a secondary container from a properly labeled primary container for one shift, one person use only operation) per the hazard communications standard, it is prudent safety practice in the laboratory to do so. A good start is placing the name of the chemical, NFPA label system information and date.

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K. Safety Data Sheets (SDS):

The revised HCS requires that the information on the SDS is presented using consistent headings in a specified sequence.

Paragraph (g) of the final rule indicates the headings of information to be included on the SDS and the order in which they are to be provided. In addition, Appendix D indicates what information is to be included under each heading. The SDS format is the same as the ANSI standard format which is widely used in the U.S. and is already familiar to many employees.

The format of the 16-section SDS should include the following sections:

Section 1. Identification
Section 2. Hazard(s) identification
Section 3. Composition/information on ingredients
Section 4. First-Aid measures
Section 5. Fire-fighting measures
Section 6. Accidental release measures
Section 7. Handling and storage
Section 8. Exposure controls/personal protection
Section 9. Physical and chemical properties
Section 10. Stability and reactivity
Section 11. Toxicological information
Section 12. Ecological information
Section 13. Disposal considerations
Section 14. Transport information
Section 15. Regulatory information
Section 16. Other information, including date of preparation or last revision

Sections 12-15 may be included in the SDS, but are not required by OSHA.

Exposure Limits:

Exposure limits are designed to protect employees from excessive exposure to hazardous substances. The limits usually are relative to the concentration of a chemical in the air. However, they also may define limits for physical agents such as noise, radiation and heat. There are a variety of exposure limits established by professional safety organizations (American Industrial Hygiene Association), governmental organizations (OSHA, EPA) and chemical manufacturers. The information can usually be found on the SDS.

Legal Limits:

Permissible Exposure Limits (PELs) are established by OSHA, 29 CFR 1910.1000, and 1910.1001 through 1910.1450. They specify the maximum amount or concentration of a chemical to which a worker may be exposed.

These are defined in three ways:

  1. Ceiling Limit (C): the concentration that must not be exceeded at any part of the workday
  2. Short-Term Exposure Limit (STEL): the maximum concentration to which workers may be exposed for a short period of time (15 minutes)
  3. Time-Weighted Average (TWA): the average concentration to which workers may be exposed for a normal, 8-hour workday.

Other Exposure Limits (legally unenforceable):

  1. Immediately Dangerous to Life and Health (IDLH) – These are conditions that pose an immediate danger to health and life by exposure. These were originally established for decision relative to respirator use.
  2. Threshold Limit Values (TLVs) – TLVs are prepared by American Conference of governmental Industrial Hygienists volunteer scientists. They show the level of exposure that workers can experience without an unreasonable risk of disease or injury.
  3. Recommended Exposure Limits (RELs) – These are recommended by the National Institute for Occupational Safety and Health. They indicate the concentration of a substance to which a worker can be exposed for up to a 10-hour workday during a 40-hour work week without adverse effects. RELs tend to be more conservative than PELs or TLVs.
  4. Workplace Environmental Exposure Limits (WEELs) – Developed by American Industrial Hygiene Association volunteers. WEELs are usually developed for chem- icals that are not widely used or for which little toxicity information is available
  5. Company-Developed Limits – Developed by company scientists. These are usually based on only short-term studies of animals and generally intended for internal company use.

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L. Chemical Tracking System:

Chemical tracking systems are a chemical database which is used to characterize the life of chemicals used in the laboratory. They should cover the history of the chemical. Remember that schools own the chemical from the cradle to the grave! There are various ways to set up these systems from index cards to a computer-based system.

The following tracking fields are recommended:

  1. Date of inventory
  2. Date chemical received
  3. Specific amount of each chemical
  4. Name, formula and grade of each chemical printed on the container's label
  5. Chemical hazard of each item [Safety Data Sheet (SDS) information and National Fire Protection Association (NFPA) hazard code]
  6. Chemical Abstract Service (CAS) registry number
  7. Source (supplier)
  8. Container type
  9. Hazard classification
  10. Required storage conditions
  11. Expiration date
  12. Storage location of each chemical
  13. Amount of chemical in the container

Regularly scheduled inventory inspections should be conducted to delete any inaccurate data in the system and dispose of outdated, unneeded, or deteriorated chemicals following the written Chemical Hygiene Plan.

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M. Centrifuge Operation:

Centrifuges can be a useful tool in the laboratory for teacher activity preparation or demonstration but need to be operated safely:

  1. Only use a rotor before the manufacturer's expiration or safe-service date.
  2. Keep a rotor-use log to prevent overuse. Check the manufacturer's recommendation or specifications as the parameters differ from one machine to another.
  3. Clean rotors and buckets with only noncorrosive solutions.
  4. Always ensure that loads are evenly balanced before doing a run.
  5. Stop the centrifuge immediately if vibration occurs.
  6. Never leave the centrifuge unattended.
  7. If corrosive or alkaline materials have been run or spilled, be sure to wash affected parts of the centrifuge immediately and allow them to air dry.
  8. Never attempt to open the door while the rotor is spinning or attempt to
  9. Stop the rotor by hand.
  10. Do not attempt to move the centrifuge while it is in operation.

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N. Electricity Hazards:

Proper grounding of flammable solvent containers and equipment is needed to prevent protection from static electricity and sparks. Dry air or low humidity fosters static electricity dangers. Sources of sparks and discharges include:

  1. Hot plate temperature controls.
  2. Light and other control switches.
  3. Pulling plugs on energized circuits.
  4. Motion of plastic or synthetic materials including clothing.
  5. Ungrounded metal objects such as screw drivers, metal electrode strips and aluminum foil.

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O. Glassware Hazards:

The leading cause of injury incidents in science laboratories usually involves the use of glassware. Borosilicate glassware is recommended for almost all laboratory work. The following procedures are recommended to reduce or eliminate injuries related to glassware in the chemistry laboratory:

  1. Always inspect glassware for cracks and rough edges before using.
  2. Discard damaged glassware in appropriate containers.
  3. Whenever possible use other types of connections including latex tubing or plastic in lieu of glass.
  4. For broken glass, wear appropriate hand protection, sweep small pieces into a pan and dispose in appropriate containers.
  5. Always give hot glass time to cool before handling.
  6. When inserting glass tubing into rubber stoppers or corks:
    1. Wear appropriate hand protection.
    2. Make sure ends are fire-polished.
    3. Lubricate the glass tubing with glycerol.
    4. Hold hands close together to limit motion of the glass.
  7. Cutting glassware steps:
    1. Score the glass tubing 1/3 the way of the circumference with a triangular file using a single stroke.
    2. Wrap the tubing in paper towels or a cloth to protect the hands.
    3. Place thumbs on both sides of the score mark opposite the score.
    4. Push away from the body with even pressure on the tube.
  8. Vacuum system glassware steps:
    1. Use only glassware that can withstand external pressure in the established atmosphere.
    2. Use Erlenmeyer-type round bottom vessels unless glassware is specifically designed for vacuum work.
    3. Always wrap vessels with duct tape to reduce glass fragment projectiles in case of an incident.
    4. Always inspect glassware and connections prior to creating the vacuum.
    5. Use a positive pressure relief device such as a liquid seal.

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Earth/Space Science-Based Physical Science

A. Astronomy:

Astronomical events such as viewing a solar eclipse are a great opportunity for learning, but safety precautions must be addressed.

  1. Never look directly at the sun, including during a solar eclipse. Permanent eye damage is likely to take place.
  2. Properly constructed pinhole viewers are a safe way to view the sun.
  3. Never view the sun directly through binoculars or telescopes. This can cause blindness.
  4. Never use sunglasses or exposed film to view the sun. They do not provide appropriate protection.

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B. Geology:

  1. Rock and Mineral Study:

    Use the following precautions in working with rocks and minerals in the laboratory:

    1. Use appropriate personal protective equipment such as chemical splash goggles, gloves and aprons.
    2. Use a heavy canvas bag when breaking up rock/mineral samples.
    3. Use proper geologic hammer technique.
    4. Never work with radioactive rocks or specimens.
  2. Geological field experience:

    Geological field experiences can be exciting and academically rewarding. The following safety precautions should be addressed in preparation for the trip:

    1. Secure information relative to medical conditions in preparation for the field activity from the school nurse and parents. Plan for administration of medication as necessary.
    2. Wear appropriate clothing for the weather conditions.
    3. Use sun sense by wearing appropriate clothing and head gear.
    4. Use appropriate footwear such as boots or sneakers. Flip flops and sandals are unacceptable.
    5. Wear safety glasses or goggles with an ANSI Z87.1 rating. Quarry and cliff type work require use of a safety helmet.
    6. Tetanus shots are suggested.
    7. Rocks and boulders should never be thrown or rolled on the field site. Never touch or try moving rotten trees.
    8. Use caution when hammering rocks.
    9. Use caution when standing near the base of a cliff.
  3. Ultraviolet Light

    The use of ultraviolet light for mineral study can be dangerous and should be done only as a teacher demonstration.

    1. Protect eyes and skin from exposure of ultraviolet transilluminators.
    2. Wear UV protection rated chemical safety goggles.
    3. Wear long sleeve shirts and lab coat with gloves.
    4. Only use a ground-fault circuit interrupter (GFCI) protected electrical receptacle for the lamp.
    5. Never operate the lamp near water sources.
    6. Never disassemble the lamp when plugged in – this is a high voltage power supply device.

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C. Water Studies:

  1. Marine Field Trips:

    Marine field trips can be useful activities to expand and apply classroom studies. Consider the following safety procedures when planning:

    1. Review weather predictions and prepare appropriately.
    2. Make sure students do not have any open wounds, sores, cuts, etc. prior to going into the water.
    3. Review field hazards and emergency plans with students prior to the start of the activity.
    4. Use foot protection and chemical splash goggles
    5. Be aware of broken glass, fish hooks, rocks and other sharps.
    6. Be watchful for poisonous or stinging marine dwellers like jellyfish, man-of-war.
    7. Always establish boundaries for the area of study.
    8. Provide life jacket for students entering water.
    9. Use sun sense by applying sun screen and appropriate clothing/hat.
    10. One adult should be on beach watch at all times in view of the boundary area.
    11. Remember to bring a cell phone, first aid kit and blanket for emergencies.
  2. Stream Tables:

    Stream tables can be effective learning tools. Use the following safety precautions:

    1. Check the table out for leaks, including drain hoses.
    2. Wipe up any spilled water immediately to avoid creating a slip and fall hazard.
    3. Electrical receptacles should be GFCI protected.
    4. Have catch water buckets or receptacles available to catch overflow.

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D. Weather Studies:

Weather studies often involve building of weather station equipment. Plan on taking the following safety precautions:

  1. Safety precautions need to be addressed and in place when using power tools, electrical devices, hand tools and sharp objects to build equipment. Be certain to file down or sand any sharp edges on materials used to construct weather station equipment after being cut. Never use equipment containing mercury such as thermometers or sling psychrometers.
  2. Only adults with formal roof walking and fall protection training should be securing equipment on the roof of a building.