Section C:  Safe Work Practices in Laboratories

1.  General Principles

• Know the hazards involved with all chemicals you will be working with before starting work in the laboratory.
• Know the types of protective equipment available and use the proper type for each job.
• Know the location of and how to use the emergency equipment in the lab in which you are working.
• All persons should wear proper personal protection wherever chemicals are stored or used.
• Visitors must wear the appropriate eye protection when visiting any chemical work area.
• Avoid consuming food or beverages in areas where chemicals are being used or stored.
• No smoking in laboratories or in areas where chemicals are stored.
• Avoid hazards to the environment by following accepted waste disposal procedures.
• All chemicals must be correctly and clearly labeled.
• Avoid distracting or startling any other worker. Practical jokes or horseplay cannot be tolerated at any time.
• Do not taste any chemical and always use the proper technique when smelling a chemical.
• Avoid unnecessary exposure to chemicals by any route (inhalation, absorption, or ingestion)
• Confine long hair and loose clothing when in the laboratory.
• Be sure to wash your hands thoroughly after working in the lab.
• Sims is a non-smoking building.

2.  Personal Protective Equipment (PPE)

• The proper eye protection is required for everyone, including visitors, entering a chemical work area.
• Know the types of protective equipment available and use the proper type for each job.

o Splash goggles are required whenever a splash hazard exist.  Safety glasses are only suitable in situations where physical hazards exist.  Proper eye protection is required whenever working with UV light.  The use of lasers requires special eye protection.

o Closed-toe shoes, preferably leather, that cover the entire foot are required for everyone entering a lab.  Shoes with high heels or made with woven material do not provide adequate protection.  Open toe shoes and sandals are not acceptable.

o Gloves are chemical specific.  Gloves suitable for one chemical may not be adequate in protecting against another.  When working with a highly toxic substance, be sure you are using the proper gloves.

o Lab coats and aprons are available for employees and students.  Heavy duty aprons are available when using concentrated acids and bases. Flame resistant lab coats should be worn when working with flammable chemicals.

O Face shields are available and are recommended when greater protection to the face and neck is required.  Face shields must always be used with goggles; face shields alone will not provide adequate protection.

• Work in a chemical hood to reduce exposure through inhalation particularly whenever chemical operations are performed that will generate aerosols, vapors and/or gases that may be harmful to one′s health.

• Maximizing Chemical Hood Efficiency

o Keep exhaust fans on at all times

O The hoods should maintain an average face velocity of 100 linear ft/min.  If the emergency alarm sounds, notify the Chemistry Instrumentation Manager at 323-4931 or the Chemistry Laboratory Manager at 323-4926.

o Keep the interior of the hood uncluttered so that airflow is not impeded

o Always keep sash closed when not actively using the hood

o Position sash so that work is performed by extending arms under the sash

o Avoid swift arm and body movements in front of the hood

o Place chemicals 6 inches behind the face of the hood

o Place equipment as far to the back as possible without blocking the bottom baffle slot

o Do not use large pieces of equipment that block the back baffle

o Do not use a hood to store chemicals or equipment

3.  Food in the Laboratory

• Contamination of food and drinking materials is a potential route for exposure to toxic substances. Food should be stored, handled, and consumed in an area free of hazardous materials.
• No food should be stored or consumed in any laboratory.
• Glassware or utensils that have been used for laboratory operations should never be used to prepare or consume food or beverages.
• Store bought items that are used for laboratory experiments must be labeled as ″For Lab Use Only″.

4.  Labeling Procedures

• All chemicals will have their manufacturer's original container warning label about hazards and should be labeled with the date of receipt and the date of initial opening.
• For smaller working amounts of chemicals that are transferred to secondary containers, those containers must be properly labeled including any health hazards. The container must be labeled with:

o The contents of the container i.e. the common name of the chemical. Chemical formulas and structural formulas are not acceptable except for small quantities of compounds synthesized in the laboratory.

o Date of transfer

O Physical and health hazards (labels available in SIMS 104, 106 and 308)

o Indicate the strength or concentration of the substance where applicable

o Faculty member′s name is needed if the chemical is being used for research and not class use.

• These labeling requirements do not apply to portable containers intended for the immediate use by the employee or student performing the transfer.  However, if the employee or student who made the transfer leaves the work area or the container is moved to another work area, the container must be labeled appropriately.  
• Unknown chemicals assigned to students for analysis in teaching or research laboratories do not need to be labeled as long as there is a procedure in place to identify the unknown substances.
• Food and over the counter store bought items purchased for laboratory use must be labeled as ″For Lab Use Only″.

5. Transporting Chemicals and Equipment

• Use caution when transporting chemicals:
• Use a nonbreakable, secured secondary container for transporting a hazardous chemicals or transport chemicals on a cart with sides that can contain a spill.
• Use the elevator when transporting chemicals between floors. Chemicals cannot be transported up and down the stairwells. Do not ride the elevator with the chemicals when transporting large quantities of chemicals. Place a prominent sign on the cart warning others not to board the elevator.
• Do not ride the elevator when transporting compressed gas cylinders or cryogens. Place a prominent sign on the cylinder warning others not to board the elevator.
• In an effort to reduce the transport of concentrated acids and bases to the 2^nd and 3^rd floors, large quantities (2.5-L bottles) of concentrated acids and base will not be stored on the 2^nd or 3^rd floors whenever practical and will be replaced with smaller working quantities. If you need a 2.5 L bottle of concentrated acid, notify the laboratory chemist.
• Use the elevator when transporting supplies and equipment between floors.

6.  Waste Disposal Procedures

• Containers:

o Containers used to accumulate waste must be in good condition (no severe rusting or apparent structural defects).

o The container used to store waste must be compatible with the waste.

o Use a container of appropriate size with a screw caped lid.  Containers with glass stoppers, rubber stoppers, corks or Parafilm are not acceptable.

o A container that begins to leak must have its contents immediately transferred to another container or the leaking container can be packed into another suitable container.

o Waste containers must remain closed except when it is necessary to add waste to the container.

o Funnels are not permitted in waste containers except when waste is being added to the container.  After addition of waste, remove funnel and tightly close the waste container.

o When disposing of chemicals, keep each different class of chemicals in a separate clearly labeled disposal container.

o The maximum size allowable for waste collection containers is 4 liters for hazardous wastes and 100 mL for acutely hazardous wastes.

O Do not fill waste containers more than 80% full.

o The outside of waste bottles must be free of chemical residue.

• Labeling
• All hazardous waste containers must be labeled at the time waste is first added to the container.
• For hazardous waste, the words "hazardous waste" must be clearly marked on the container.
• In satellite accumulation point, the contents of the waste must be clearly marked on the container with chemical names, abbreviations and chemical formulas are not acceptable.
• When a hazardous waste container is full and ready to be moved to the waste accumulation point (the chemical storage building), the container must be labeled with a University, pre-printed, self-adhesive yellow hazardous waste label.  The label must be completely filled out with the following information:
• Name and phone number of Principal Investigator/Laboratory Supervisor (waste generator)
• University department, building and laboratory number
• Contents of the container, listing the names of all chemicals added to the container (use chemical names, abbreviations and chemical/structural formulas are not acceptable)
• The percentage of each chemical if more than one chemical is added to the container. For mixtures, the name of the chemicals must be listed from greatest percentage to least percentage.
• When completing the University, pre-printed yellow hazardous waste label, do not fill in the accumulation date or the EPA Hazardous Waste Code.  The accumulation date is added to the label when the container is move to the waste accumulation area and inventoried.  The EPA Hazardous Waste Code is determined by the Office of Environmental Health and Safety and added to the container when it is moved to the waste accumulation area.

• Accumulation Points (the outside chemical storage building):

o Waste will be stored in the chemical storage building until it is picked up and removed from campus.

o Disposal of waste from campus must occur every 180 days or 270 days if the waste is being transported to a facility more than 200 miles away.  The Office of Environmental Health and Safety is responsible for the removal of waste from campus.

o Accumulation points must be inspected weekly.  The Office of Environmental Health and Safety is responsible for the inspection of the accumulation points.

o All hazardous waste containers must have a yellow hazardous waste label on the bottle before being transported to the chemical storage building.

o When the Chemistry Department puts a hazardous waste container in the accumulation point, the laboratory chemist will notify EHS.

o EHS maintains an inventory of the accumulation points.

o Must have the appropriate spill control materials available.

• Satellite Accumulation Points:
• The satellite accumulation point must be under the control of the operator of the process that generates the waste and must be near the point of generation.
• All containers of hazardous waste stored in a satellite accumulation point must be labeled with the words ″Hazardous Waste″ and the contents of the waste.
• All satellite accumulation points must be identified as such.
• Containers must be in good condition
• Full hazardous waste containers or hazardous waste containers that are no longer being used must be moved to the accumulation point within 3 days. The faculty member responsible for the lab in which the waste was generated must be sure the container is properly labeled with a University yellow waste label completely filled out and notify the laboratory chemist who will inventory the waste, move it to the appropriate accumulation point and notify EHS.
• Waste cannot be transported from one satellite accumulation point to another. 
• Container holding hazardous waste must always be kept closed during accumulation except when it is necessary to add or remove waste.
• No single satellite accumulation point may hold more than 55 gallons of hazardous waste or more than 1 quart of acute hazardous waste at any one time.
• Must have the appropriate spill control materials available.

• Waste Generator Responsibilities:

o Select chemicals carefully, become familiar with the hazards of each chemical and to manage and dispose of all hazardous wastes in compliance with EPA/DHEC regulations and Winthrop University policies.

o Properly identify hazardous waste, select compatible containers and to segregate and store hazardous wastes to ensure the safety of those working in the laboratory.

o Ensure that all hazardous waste containers are properly labeled and kept clean of waste residue.

o Ensure that hazardous waste containers are always kept closed except when adding or removing waste from the container. A funnel in a waste container is not considered closed.

o Ensure that different waste streams (i.e. radioactive, chemical or biological) are not mixed together. Separate waste materials as much as is feasibly possible- if you must combine materials, try to keep the chemistry as pure as possible. Do not mix incompatible wastes.

o Initiate a meaningful waste minimization plan through substitution, scale reduction, purchase control and/or recycling.

o Ensure that students working in the laboratory understand and follow these responsibilities.

o Faculty must ensure that all waste has been removed from their laboratories at the end of each semester.

• Training Requirements
• All employees must be thoroughly familiar with waste handling and emergency procedures relevant to their responsibilities.
• New employees that work with hazardous waste must be trained within 6 months.
• All employees must take part in an annual review of the training program.

• General Waste Information

o Broken thermometers may contain mercury in the fragment and should be disposed of in a hazardous waste container designated for broken thermometers.

o Never put chemicals down the drain unless they are neutralized and allowed by local regulations, i.e. neutralized chromic acid contains chromium, a health hazard, which must be disposed of as a hazardous waste.

7.  Special Safety Considerations

Centrifuges

• For tabletop centrifuges, make sure that they are properly secured and anchored in a location where vibration will not cause glassware or equipment to fall.
• Never leave the centrifuge until full operating speed has been obtained and the machine appears to be running safely without excessive vibration.
• If a vibration occurs, stop the centrifuge immediately and check the counter-balance load. Check swing-out buckets for clearance and support.
• Regularly clean rotors with noncorrosive cleaning solutions.
• For larger centrifuges, ensure regularly schedule maintenance has been performed and has been recorded in the logbook.

 Ultraviolet Lamps

• All radiation shorter than 250 nm should be considered dangerous.
• Protective safety glasses with UV-absorbing lenses should be worn when the eye may be accidentally exposed to light in this wavelength region.
• It is advisable to operate such UV systems in a completely closed radiation box.
• Skin areas exposed to UV can receive painful burns, so precautions to protect skin must be taken.
• Handling of mercury arc lamps will deposit oils from the skin onto the outside glass surface causing local overheating of the lamp. Over time deposits on the inside of the glass may absorb UV and cause overheating. Do not handle lamps with bare skin. Use disposable gloves or Kimwipes to handle light sources.
• Whenever possible, UV sources should be adequately cooled and operated within an enclosure designed to prevent damage by explosion of glass fragments and leakage of mercury vapor.

Cold Room

• General Cold Room Procedures
• Keep your time working in the cold room to a minimum.  If prolonged periods of time must be spent in the cold room, please wear appropriate PPE (gloves, hat, jacket, etc.)
• Do not place any objects outside the cold room door.  This could prevent the door from opening and trapping someone inside.
• The cold room floors are metal and will conduct electricity.  Use extreme caution when working with electrical equipment.  Use rubber-insulating mats on the floor to avoid shocks.
• During normal working hours, students must either enter the cold room with someone else, or there must be other people in the biochemistry 303 suite.  If there is no one in the biochemistry area, the student must find another faculty member on the floor and inform them that they are entering the room.
• Students are not allowed to enter the cold room after hours unless their research advisor is present.
• Always turn the light to the cold room off when you exit the room.  The light is connected to a sign in the hallway informing others that the room is in use. 

• Emergency Procedures for the Cold Room
• If an alarm sounds, leave the room immediately and call Facilities Management at 323-2261.
• If you experience dizziness or lightheadedness while working in the room, push the panic button and leave the room immediately.  In a life-threatening emergency, call 9-911 or -3333 immediately.  For non-life threatening incidents, employees will need to notify the chair and call the Office of Environmental Health and Safety at -2328 or 242-9545 so that they can be medically evaluated.  If a student experiences dizziness or lightheadedness, call public safety at -3333.
• Pushing on the door from inside should open the door.  If you cannot get the door opened from the inside, push the lever down to open the door.  If that does not work, there is a black knob by the door.  If you turn the knob 90 counterclockwise, it will remove the lock so that the door can be opened.
• The cold room is wired to the back-up generator.  Thus, if the electricity were to go out in the building, the cold room and its oxygen sensor would still have power.

• Safe Chemical Use in the Cold Room
• Do not use any flammable or toxic chemicals, corrosive acids, asphyxiants or open flames in the cold room.  The room does not have ventilation to exhaust such chemicals resulting in possible personal overexposure.
• Volatile flammable chemicals can cause fires or explosions.  The cold room has exposed motors for circulation fans and thus, it a potential ignition source.
• Corrosive acids can corrode cooling coils in the refrigeration system leading to refrigerant leaks.
• Asphyxiant gases can displace oxygen in the room.  Do not use liquid nitrogen or dry ice in the cold room.
• Compressed gases cannot be stored in the cold room.  When using compressed gases, be sure connections are secure to minimize leakage.  If the oxygen sensor alarm sounds when using a compressed gas, leave the cold room immediately.  Be sure to turn the gas off when you are finished using it.
• Dry ice cannot be stored in the cold room.  The release of carbon dioxide can lower oxygen levels in the room.

• Preventing Mold Growth in the Cold Room
• Keep the door firmly shut to avoid condensation on interior surfaces.
• Do not have open containers of water or aqueous solutions.
• Clean up all liquid spills immediately. Use the spill kit when cleaning up hazardous materials.
• Report any water leaks or dripping faucets to Facilities Management @ 323-2261   immediately
• Store paper products in closed plastic containers.  Do not store cardboard or other porous organic materials in the room. 

• Cold Room Maintenance
• The oxygen sensor in the room must be inspected and tested to ensure its accuracy.  The power/batteries to the oxygen sensors should be tested weekly and the alarm should be tested monthly.
• The oxygen sensor will be replaced at least every two years. 
• The cold room will be inspected yearly by facilities management for leaks, temperature control, and piping integrity.   

Lasers

• The American National Standards Institute has established safety rules and ratings for lasers.
• Class 1 lasers denote lasers that cannot produce a hazard under normal operating conditions.
• Class 2 lasers denote low-power visible lasers that do not normally present a hazard, but may if viewed directly for extended periods of time. Class 2 lasers present no danger to the skin, and the beam does not even feel warm on the skin.
• Class 3 lasers are lasers that can produce a hazard if viewed directly.
• Class 4 lasers can produce a hazard not only from direct viewing or a specular reflection but also from diffuse reflection.
• Lasers with a power of less than 1 mW are classified as class 2 lasers and are the most appropriate for use in the teaching laboratory.
• Although 1 mW seems small compared to a 100 W light bulb, all the energy is concentrated to a roughly 1 mm2 area, making the energy per unit area very large. Because the eye can focus the already intense laser beam onto a small area of the retina, permanent damage can result from extended viewing of the direct beam.
• In addition, the eye becomes sore with prolonged viewing of diffuse of reflected light. All experiments should be set up to minimize the chances of such exposure.
• The basic safety rule is to avoid looking directly into the laser beam.
• Use of class 3 and class 4 lasers require protective eye goggles and other safety precautions. These lasers are generally too powerful for use by beginning students, but are often necessary for advanced physical chemistry and analytical chemistry laboratories. In such cases, a separate set of safety guidelines will be published for work with these lasers.

Reduced Pressure Operations

• Vacuum desiccators should be protected by covering with cloth-backed friction or duct tape or enclosed in a box or approved shielding device for protection in case of implosion.
• Only chemicals being protected from moisture should be stored in a desiccator.
• Before opening, make sure the atmospheric pressure has been restored; frozen lids can be loosened by a single edge razor blade as a wedge that is then tapped with a block to raise the lid.
• All vacuum lines should be trapped, and shielding should be used whenever the apparatus is under reduced pressure.
• Water aspirators for reduced pressure are mainly used for filtration purposes; they are sometimes used for reduced pressure for rotary evaporation equipment.
• Only equipment approved for this purpose should be used.
• Never apply reduced pressure to a flat-bottomed flask unless it is a heavy-walled filter flask designed for the purpose.
• Place a trap and check valve between the aspirator and apparatus so that water cannot be sucked back into the system if the water pressure should fall unexpectedly while filtering.
• If vacuum pumps are used, a cold trap should be placed between the apparatus and the vacuum pump, so that volatiles from a reaction or distillation do not get into the pump oil or out into the atmosphere of the laboratory.
• When possible, vacuum pump exhausts should be vented to a hood.

Cooling Baths and Cold Traps

• When ice water is not cool enough for use, salt and ice may be used. For even lower temperatures, dry ice may be used with an organic liquid.
• An ideal cooling liquid to be used with dry ice should be nontoxic, low viscosity, nonflammable, and low volatility.
• Ether, acetone, and butanone are too flammable and volatile and should not be used.
• The following meet the criteria for use with dry ice in cooling baths:
1. Ethylene glycol or propylene glycol in a 3:2 ratio with water and thinned with isopropyl alcohol
2. Isopropyl alcohol
3. Some glycol ethers
• Cryogenic coolants should always be used with caution; cryogenic liquids must be handled in properly vented containers.
• Be aware that very low temperature coolants, such as liquid nitrogen, may condense oxygen and cause an explosion with combustible materials.
• Avoid pouring cold liquid onto the edge of a glass Dewar flask when filling because the flask may break and implode.
• For the same reason do not pour a cryogenic liquid out of a glass Dewar flask; use mild air pressure or a siphon.
• Metal and plastic Dewar-type flasks are preferable and eliminate this problem.
• Never use a household thermos in place of a Dewar flask.
• Dry Ice should be handled with caution:
• Do not lower your head into a dry ice chest; no oxygen is present, suffocation can occur.
• Do not handle dry ice with bare hands; if the skin is even slightly moist, severe burns can result.
• Use leather or suitable cryo-gloves to handle dry ice; when chipping dry ice, wear goggles.

Oil and Sand Baths

• When hot oil or sand is used for heating, extreme care must be taken to avoid:
• Overturning the bath
• Hazardous splattering caused by water falling into hot oil or sand
• Smoking caused by decomposition of the oil or of organic materials in the oil
• Fire caused by overheated oil bursting into flames.
• Whenever possible, use sand baths for heating rather than oil baths; when using oil baths, consider the following:
• Operating temperature and temperature control devices
• Type of oil used (silicone oil, Dow Corning 550, is suggested for most heating needs)
• Available ventilation
• Method of cooling the hot oil
• Storage of oil for reuse
• Location away from possible sources of spilled chemicals or water

8.  Faculty and Student Research Chemical Hygiene and Safety

Research is an important part of undergraduate education and requires special safety considerations.  Each research mentor is responsible for ensuring that all research they carry out or mentor is conducted in accordance with the policies, principles, and procedures outlined in the Department′s Chemical Hygiene Plan.

Laboratory Supervision Requirements for Students

• Working hours are 8 am −6 pm and require that following conditions be met:
• The proper personal protective equipment must be used and all laboratory procedures must be carried out in accordance with the CHP.
• Research students are responsible for informing their research advisor that they are in lab working.
• A faculty member must be present on the floor in which a student is working and the student must notify the faculty member as to where they will be working.  This rule also applies to students using computers in a laboratory during the hours of 8 am to 6 pm.
• If a faculty mentor is going to be out of their office for the day, they must arrange with another faculty member to supervise their students for the day.  Research students must be notified of your absence and are responsible for reporting to the designated faculty member.

• Laboratory work after hours
• No laboratory work can be conducted by students outside normal working hours if the student′s research mentor is not present.
• Exceptions must be approved by the safety committee and will be limited to activities that are essential to the research, but do not involve hazardous chemicals or procedures.
• Unsupervised after hours computer use in laboratories is not allowed due to the hazardous nature of the laboratory.  Students can use laboratory computers for data analysis after hours if there is a faculty member on the floor, and the faculty member is aware of the student′s presence. 
• When entering Sims after hours, you must bring someone with you not only for laboratory safety reasons, but also for your own personal safety.

Student Training and Information Requirements:

• Any student conducting research for academic credit will be required to submit to the research course instructor, as part of their grade, the following:
• A list of chemicals that will be used
• The hazards associated with the use of each substance
• The proper personal protective equipment that must be used
• A detailed description of any operations that will be performed outside normal working hours, including whether or not such operations require supervision
  
  
• Students must have access to MSDS′s and be made aware of the hazards associated with the substances they will be working with.
• The department′s safety coordinator will train research students in general laboratory procedures and students are required to take a safety quiz yearly and pass with a 100%.
• Individual research advisors will train their research students in the specific chemical and physical hazards that exist in their lab.
•  Once students are adequately trained, they must demonstrate competence in the techniques they will be using before being allowed to carry out these independently.
• Some techniques must only be done under direct faculty supervision.
• Students must be trained on the chemical disposal procedures to be used; on labeling requirements for all chemicals or solutions they prepare; and on guidelines for laboratory storage, housekeeping, and cleanliness requirements that must be met before they can depart each day.
• Students are not allowed to work in lab alone.
• Students must know and must demonstrate competence in the specific prudent safety practices necessary for the work being done.

Completion of Student Research Project

• The research course director and faculty research mentors will not assign satisfactory final research grades to students until they have:
• Returned chemicals used to their proper location
• Returned all equipment
• Properly labeled all waste and taken it to a location identified by the lab chemist Properly disposed of all calibration solutions
• Removed and properly disposed of all materials stored in refrigerators and freezers

Research Chemical Inventory Management

• At the end of each academic year, each faculty member will inventory their research chemicals, identify materials that are no longer necessary, and properly dispose of excesses.  This includes any substances stored in refrigerators or freezers.

• Chemicals will be ordered in the smallest possible quantities that are prudent, even at the expense of higher long-term costs.  The goal is to minimize on-hand chemical inventories.

9.  Faculty Research Project Summary Requirements

Each research advisor must submit to the Department Safety Committee a project summary.  Project summaries are due as follows:

• An updated summary is due the Friday of the first week of classes in January.
• If you are starting a new project, a project summary is due the week before the start of classes in the semester in which the research will take place.
• If you are starting a new project for the summer, a project summary is due May 1, so that the safety committee can review the information before May 15.

Each project summary should address the following:

• An overview of the research project including objectives.
• A list of all chemicals that are expected to be used.  If any particularly hazardous chemicals will be used by the student, the research advisor must include the potential hazards associated with the use of such chemicals, the proposed procedures, justification for why the proposed procedure must be used, and any special safety and precautionary steps that will be taken.
• Particularly hazardous chemicals include corrosive, flammable, highly reactive or explosive chemicals, or toxic chemicals such as carcinogens, reproductive toxins, embryo toxins, chemicals of high chronic toxicity, or materials exhibiting a high degree of acute toxicity
• Include your lab′s policy on the use of personal protective equipment.
• Clearly indicate what activities students can and cannot perform alone
• Any activity in which an accident could happen cannot be performed by a student unsupervised
• Will any unsupervised activities need to be performed outside working hours (8am to 6 pm)?

• If so, clearly state what these activities will involve, and when and how often they will occur.
• Unsupervised activities taking place outside normal working hours must be approved by the Department Safety Committee.
• Approval will be limited to activities that are essential to the research, but do not involve hazardous chemicals or procedures

• Upon the completion of a student research project, how will you ensure that the student has:

o Returned all chemicals to their proper location

o Returned all equipment

o Labeled all waste properly and has notified stockroom personal for proper disposal

o Disposed of any unused chemicals and/or solutions that will no longer be used for this project

o Removed and properly disposed of all materials stored in refrigerators and freezers