Education and Early Childhood Learning

Science Safety

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Chapter 6

Storage and Disposal

Chemical Storage
Disposal of Biological Materials and Chemicals

Chemical Storage

Proper Storage Prevents Accidents

In some cases, chemicals have been stored in Senior Years schools using a nonclassified storage system that places chemicals on shelves in an alphabetical sequence. In many cases, flammable storage cabinets were used to isolate flammable materials. This made it possible for highly reactive substances such as oxidizing agents and reducing agents to be placed side by side on a shelf. Poor housekeeping could result in spontaneous reactions.

To prevent accidents, proper chemical storage should involve isolating major classes of substances. The model for chemical storage described below prevents both the storage of flammable solvents near reactive chemicals (which could cause a spontaneous fire), and the storage of corrosive liquids (e.g., H₂SO₄) in the same area as toxicants (which could lead to the release of poisonous fumes into the atmosphere).

A Suggested Model for Chemical Storage

This model represents an effective yet economically feasible model which can be adapted to any school chemical storage situation.

The characteristics of an effective chemical storage facility include

• locking doors that isolate the chemical storage area from preparation areas and classrooms
• using a WHMIS-approved labelling system that segregates all chemicals into classes to make it easy to access and replace them in their proper storage position
• using an effective ventilation system

A chemical storage room must be secure to prevent theft and unwarranted use of chemical stock. A separate key from those used to enter classrooms or preparation areas is essential. Allow only authorized personnel to have access to the chemical storage room.

The room must be adequately vented as per standards and codes with a fan that runs continuously. Install explosion-proof lights, switches, and fan motor housing to prevent fires due to electrical shorts or sparks in faulty switches. Ground fault interrupter (GFI) circuits should be installed, especially near sinks. Construct ceilings and walls of gypsum boards or some similar non-combustible material.

The chemical storage area must house all of the chemical stock used in the science program. A large Senior Years school (800-1000 students) may require a room with approximately 150 m of shelf space. Smaller schools, offering only Middle Years science, may require 80 m of shelf space. Combined Middle and Senior Years may require 200 m of shelf space.

Problems often arise because of the quantities of chemical stock ordered from year to year. If the school is unable to accommodate its chemical stores in a facility similar to the one described in this section, schools should examine closely the amount of material they have in storage. As a general rule, do not order more chemical stock than the school plans to use annually.

An example of a typical chemical storage room is illustrated below.

 

Storage Suggestions Include

• avoiding floor chemical storage (even temporarily)
• avoiding chemical storage on top of shelf unit
• avoiding chemicals stored above eye level
• fastening shelf assemblies securely to a wall (avoid island shelf assemblies)
• making shelving assemblies of wood
• providing lips on all shelves to prevent roll-off
• avoiding metal, adjustable shelf supports or clips (fixed, wooden supports are preferred)
• storing both inorganic and organic acids in a dedicated acid cabinet with doors
• storing nitric acid isolated from other chemicals
• storing flammables in a dedicated metal cabinet with doors
• storing extremely toxic poisons in a locked cabinet

 

 

Acids

Store acid bottles in a corrosion-resistant plastic tray close to the floor. Concentrated nitric acid should be stored in a separate wooden compartment that has wooden dowel hinges and external locking attachments (no metal on inside surfaces). The cabinet must be vented to permit a continuous flow of air through it. Ideally, this cabinet should be in the chemical storage room.

Flammable Solvents

Flammable solvents must be stored in cool areas inside an approved (Underwriter Laboratories [UL] or Canadian Standards Association [CSA]) flammables cabinet. The cabinet must be vented to permit a continuous flow of air through it; if this is not possible, then it must be vented into a storage area that has continuous ventilation.

In general, a 120 L cabinet houses all the flammable solvents needed for most schools with more than 700 students. A 90 L cabinet is adequate for smaller schools. Many schools currently store too large a quantity of flammable solvents. In general, schools do not require more than 4 L of any one solvent in one year. It is recommended that a total of not more than 50 L of solvent be stored in any school.

Be certain the cabinet contains only flammable substances and absolutely no oxidizers (e.g., sodium peroxide*, a strong oxidizer will spontaneously react with solvents causing a fire/explosion hazard.)

* Must not be present in school laboratories or storerooms.

Toxic Substances

Toxic substances have the capacity to injure the body by direct chemical action. They include corrosive as well as poisonous materials. Refer to Schedule B of Manitoba Regulation 52/88 which is part of The Workplace Safety and Health Act (chapter W210) for a list of designated materials.

Poisons should be stored above waist height, preferably in a locked cabinet.

Alternatives to a Separate Chemical Storage Room

While a separate room is preferable for chemical storage, the principles of proper chemical storage can be maintained without a separate room. If a science preparation room is used as the chemical storage room, it is appropriate to

• prevent the accumulation of harmful vapours by adequately and continuously venting to the exterior with an exhaust fan
• equip the room with a properly vented flammables cabinet to house all solvents and flammable materials
• store acid and basic (alkaline) solutions separately in closed and vented cabinets
• keep toxic chemicals (poisons) in a separate locked cupboard
• keep oxidizers and reducers on separate shelves as far from each other as possible
• store hydrolyzing (water reactive) solids in a separate area
• store alphabetically general miscellaneous chemicals if they are compatible

This is a challenging system to adequately maintain. Good housekeeping can be a problem when chemical storage is not housed in a separate room.

Note: When the science preparation room is used as the chemical storage room, it must not be used as a general teacher preparation area/working station (i.e., teachers are not to be present in the room other than when dealing with chemicals).

The disposal of biological materials, waste chemicals, and potentially hazardous materials is a necessary and common occurrence in school science laboratories. This section does not provide specific detailed information for the disposal of such materials, but indicates what resources the teacher or technician can consult to dispose of biological materials and waste chemicals properly.

Disposal of Biological Materials and Chemicals

The disposal of hazardous waste materials or "special wastes" is governed by two pieces of legislation in Manitoba: The Environment Act and The Dangerous Goods Handling and Transportation Act. Miller Environmental Corporation, a commercial corporation, provides analysis and identification, on-site packaging and handling, transportation to licensed facilities, reuse or recycling, and treatment and disposal services. Contact their office for more information (see Appendix J). In addition, a number of commercial waste management services are found in the yellow pages of the local telephone directory.

Disposal of Biological Materials

The greatest hazards in the biology classroom come from dissected organisms and microbiological specimens. Ideally, much of this material should be incinerated. If this is impossible, place carcasses and animal remains in heavy opaque, well-sealed biohazard plastic bags, and send them to the local landfill.

Burying the remains near the school may result in wild animals and pets digging them up. Autoclave used petri dishes and cultures in autoclavable disposable bags before disposal. Autoclave liquid cultures and pour into a drain with large amounts of water. Dispose of syringes, needles, scalpels, and razor blades in a metal or thick plastic container which is labelled.

Disposal of Chemicals

The four methods of dealing with chemical wastes include

• flushing into drains
• landfilling
• incinerating
• reclaiming

Do-it-yourself disposal can be costly. Useful references (see Bibliography) for disposal on your own are

• Prudent Practices for Handling Hazardous Chemicals in Laboratories
• Flinn Chemical Catalogue & Reference Manual (free)

Small Chemical Spills

Weak acids and bases can be flushed down sinks with large quantities of water. Small amounts of solvents can be evaporated in a fume hood. Small spills of poisonous or highly reactive materials must be dealt with responsibly. Mercury is highly toxic in small amounts. A broken thermometer should be cleaned up immediately, using a mercury spill kit, packaged and sent to the Miller Environmental Corporation.

Large Chemical Spills

Concentrated acid and base spills require protective clothing/equipment during cleanup and disposal. Face shields, rubber gloves, rubber boots, and lab coats should be worn. Large spill kit pillows can be used to absorb and neutralize these spills. If spill kits are not available, then acids must be neutralized with dry sodium bicarbonate and bases with diluted hydrochloric or acetic acid.

Neutralized spills must be further diluted with plenty of water. If a floor drain exists, it is usually permissible to wash the mixture down the drain with plenty of water (provided it is not prohibited by municipal by-laws or special waste regulations). Alternatively, absorbent materials (Vermiculite or diatomaceous earth) may be used to soak up the solution. The resulting mixture is then bagged, labelled, and sent to the Miller Environmental Corporation.

Spill Kits

The items listed below will enable you to deal with most common spills of acids, alkaline solutions, flammable solvents, and mercury. Commercial spill kits, available from most scientific supply companies, are more convenient to use and are recommended.

• Vermiculite (6 kg) and activated charcoal (1 kg) mixture
• bentonite or Kitty Litter (10 kg)
• sodium bicarbonate (3-4 kg of dry solid)
• weak acid (liquid or solid)
• various size freezer bags with ties
• dustpan
• whisk broom
• labels and tape
• metal containers for flammable wastes

Disposal Through the Miller Environmental Corporation

Before removing unwanted chemicals, examine and follow the chemical disposal policy of the school or division. These chemicals may be handled by the Miller Environmental Corporation. Obtain copies of their brochures, Full Service Solutions to Hazardous Waste Problems and Managing Your Own Hazardous Waste. Prepare materials for delivery by

• placing each chemical container (e.g., jar, tin) in a heavy clear plastic bag (freezer bags work well)
• sealing the bag and labelling the contents
• packing the bag in a box using vermiculite, styrofoam chips, or similar packing material
• labelling, then sealing the box with tape
• keeping acids and reducing agents separate (if the quantity of disposables is large, pack chemicals from different hazard groupings in separate boxes)
• delivering all materials to the Miller Environmental Corporation (it will be kept in their storage facility for collection and eventual transfer to a proper waste management facility ­ check first with your administrator)
• avoiding packing explosive or highly reactive substances (N.F.P.A. Code -- Reactivity 4)

Contact the Miller Environmental Corporation office for advice on chemical compatibility groups and special packaging information (see Appendix J for address and telephone).

Teaching About Spill Clean-up

It is important that students have practical experience in spill clean-up and disposal procedures. A sample lesson plan is provided below, but teachers are encouraged to discuss and demonstrate spill clean-up procedures in the context of all laboratory activities.

Sample Lesson Plan

Time: Two or three fifteen-minute lessons.

Placement: During any chemistry unit in Middle or Senior Years.

• Discussion: When distributing mercury thermometers outline the proper procedure if one should break. Discuss the hazards associated with mercury vapour.
• Demonstration: Simulate a spill of sulphuric acid from a beaker. Indicate the need to keep the bench area clean and clear of books, papers, and purses. Show students the proper clean-up procedure and insist on the importance of telling the teacher immediately of an accident, spill, or contact of chemicals with skin or clothing.
• Demonstration: Show students how to clean up an ethanol spill.
• Practice: Use simulated spills (water) to have students practice clean-up procedures. You may designate some spills as specific substances or tell the students to clean the spill as if it were an unknown liquid. Be sure to include questions on these procedures on safety quizzes or examinations.