In addition to the chemical hazards found in laboratories, there are also numerous physical hazards encountered by laboratory staff on a day-to-day basis. As with chemical hazards, having good awareness of these hazards, good preplanning, use of personal protective equipment and following basic safety rules can go a long way in preventing accidents involving physical hazards.
It is the responsibility of the Principal Investigator and laboratory supervisor to ensure that staff and students in laboratories under their supervision are provided with adequate training and information specific to the physical hazards found within their laboratories.
Having a properly lighted work area is essential to working safely. A couple of key points to remember about proper lighting:
- Lighting should be adequate for safe illumination of all work areas (100-200 lumens for laboratories). For more information, see the PDC Design and Construction Standard 16500 – Lighting.
- Light bulbs that are mounted low and susceptible to contact should be guarded.
- If the risk of electrocution exists when changing light bulbs, practice lockout/tagout.
- For replacement and disposal of standard room lighting (fluorescent) bulbs contact CPFM Customer Service Center at 346-2319. For disposal of specialty lab bulbs (fluorescent bulbs, UV bulbs) contact EHS at 346-2348.
- As an energy conservation measure, please remember to turn off your lights when you leave your lab.
Lead acid batteries contain corrosive liquids and also generate hydrogen gas during charging which poses an explosion hazard. The following guidelines should be followed for battery charging areas:
- A “No smoking” sign should be posted.
- Before working, remove all jewelry from hands and arms and any dangling jewelry to prevent accidental contact with battery connections (this can cause sparks that can ignite vapors).
- Always wear appropriate PPE such as rubber or synthetic aprons, splash goggles (ideally in combination with a face shield), and thick Neoprene, Viton, or Butyl gloves.
- A plumbed emergency eyewash station must be readily available near the station (hand held eyewash bottles do not meet this criterion.)
- A class B rated fire extinguisher needs to be readily available. If none is available, contact The University Fire Marshal’s Office at 541-346-9295.
- Ensure there is adequate ventilation available to prevent the buildup of potentially flammable and explosive gases.
- Keep all ignition sources away from the area.
- Stand clear of batteries while charging.
- Keep vent caps tight and level.
- Only use the appropriate equipment for charging.
- Store unused batteries in secondary containment to prevent spills.
- Have an acid spill kit available. The waste from a spill may contain lead and neutralized wastes may be toxic. Contact EHS at 541-346-9058 for hazardous waste disposal.
- Properly dispose of your used batteries.
HEAT AND HEATING DEVICES
Heat hazards within laboratories can occur from a number of sources. The following are some simple guidelines that can help to prevent heat related injuries.
- Heating devices should be set up on a sturdy fixture and away from any ignitable materials (such as flammable solvents, paper products and other combustibles).
- Do not leave open flames (from Bunsen burners) unattended.
- Bunsen burners with an open flame should not be placed under a shelf or other low overhang.
- Heating devices should not be installed near drench showers or other water spraying apparatus due to electrical shock concerns and potential splattering of hot water.
- Heating devices should have a backup power cutoff or temperature controllers to prevent overheating. If a backup controller is used, an alarm should notify the user that the main controller has failed.
- Provisions should be included in processes to make sure reaction temperatures do not cause violent reactions and a means to cool the dangerous reactions should be available.
- Post signs to warn people of the heat hazard to prevent burns
When using ovens, the follow additional guidelines should be followed:
- Heat generated should be adequately removed from the area.
- If toxic, flammable, or otherwise hazardous chemicals are evolved from the oven, then only use ovens with a single pass through design where air is ventilated out of the lab and the exhausted air is not allowed to come into contact with electrical components or heating elements.
Heating flammables should only be done with a heating mantle or steam bath. When using heating baths, these additional guidelines should be followed:
- Heating baths should be durable and set up with firm support.
- Since combustible liquids are often used in heat baths, the thermostat should be set so the temperature never rises above the flash point of the liquid. Check the SDS for the chemical to determine the flashpoint. Compare that flashpoint with the expected temperature of the reaction to gauge risk of starting a fire.
Another form of heat hazard occurs when working in a high heat area. If your body cannot regulate its temperature, it overheats and suffers some degree of heat stress. This can occur very suddenly and, if left unrecognized and untreated, can lead to very serious health effects.
Heat stress symptoms range from mild (e.g., fainting, cramps, or heat rash) to severe (e.g., heat exhaustion or heat stroke). Symptoms of mild to moderate heat stress can include: sweating, clammy skin, fatigue, decreased strength, loss of coordination and muscle control, dizziness, nausea, and irritability. You should move the victim to a cool place and give plenty of fluids. Place cool compresses on forehead, neck, and under their armpits.
Heat stroke is a medical emergency. It can cause permanent damage to the brain and vital organs, or even death. Heat stroke can occur suddenly, with little warning. Symptoms of heat stroke may include: no sweating (in some cases victim may sweat profusely), high temperature (103? or more), red, hot, and dry skin, rapid and strong pulse, throbbing headache, dizziness, nausea, convulsions, delirious behavior, unconsciousness, or coma.
In the case of heat stroke, call 911 and get medical assistance ASAP! In the meantime, move the victim to a cool place, cool the person quickly by sponging with cool water and fanning, and offer a conscious person a half-glass of water every 15 minutes.
There are a number of factors that affect your body’s temperature regulation:
- Radiant heat sources such as the sun or a furnace.
- Increased humidity causes decreased sweat evaporation.
- Decreased air movement causes decreased sweat evaporation.
As ambient temperature rises, your body temperature rises and its ability to regulate decreases. You should be especially careful if:
- You just started a job involving physical work in a hot environment.
- You are ill, overweight, physically unfit, or on medication that can cause dehydration.
- You have been drinking alcohol.
- You have had a previous heat stress disorder.
In order to prevent heat stress, please follow these recommendations:
- Acclimatize your body to the heat. Gradually increase the time you spend in the heat. Most people acclimatize to warmer temperatures in 4-7 days. Acclimatization is lost when you have been away from the heat for one week or more. When you return, you must repeat the acclimatization process.
- Drink at least 4-8 ounces of fluid every 15-20 minutes to maintain proper balance during hot and/or humid environments. THIRST IS NOT A GOOD INDICATOR OF DEHYDRATION. Fluid intake must continue until well after thirst has been quenched.
- During prolonged heat exposure or heavy workload, a carbohydrate-electrolyte beverage is beneficial.
- Alternate work and rest cycles to prevent an overexposure to heat. Rest cycles should include relocation to a cooler environment.
- Perform the heaviest workloads in the cooler part of the day.
- There should be no alcohol consumption during periods of high heat exposure.
- Eat light, preferably cold meals. Fatty foods are harder to digest in hot weather.
Because many chemicals captured in cold traps are hazardous, care should be taken and appropriate protective equipment should be worn when handling these chemicals. Hazards include flammability, toxicity, and cryogenic temperatures, which can burn the skin.
If liquid nitrogen is used, the chamber should be evacuated before charging the system with coolant. Since oxygen in air has a higher boiling point than nitrogen, liquid oxygen can be produced and cause an explosion hazard, both from rapid expansion of condensed gas and from exothermic oxidation of organic material upon thawing.
Boiling and splashing generally occur when charging (cooling) a warm container, so stand clear and wear appropriate protective equipment. Items should be added slowly and in small amounts to minimize splash.
A blue tint to liquid nitrogen indicates contamination with oxygen and represents an explosion hazard. Contaminated liquid nitrogen should be disposed of appropriately.
If working under vacuum see the “reduced pressure” section.
Autoclaves have the following potential hazards:
- Heat, steam, and pressure
- Thermal burns from steam and hot liquids
- Cuts from exploding glass
Some general safety guidelines to follow when using autoclaves:
- All users should be given training in proper operating procedures for using the autoclave. Read the owner’s manual before using the autoclave for the first time. Operating instructions should be posted near the autoclave. Follow the manufacturer’s directions for loading the autoclave. Be sure to close and latch the autoclave door.
- Some kinds of bottles containing liquids can crack in the autoclave, or when they are removed from the autoclave. Use a tray to provide secondary containment in case of a spill, and add a little water to the tray to ensure even heating.
- Only fill bottles half way to allow for liquid expansion and loosen screw caps on bottles and tubes of liquid before autoclaving, to prevent them from shattering.
- Do not overload the autoclave compartment and allow for enough space between items for the steam to circulate.
- Be aware that liquids, especially in large quantities, can be superheated when the autoclave is opened. Jarring them may cause sudden boiling, and result in burns.
- At the end of the run, open the autoclave slowly: first open the door only a crack to let any steam escape slowly for several minutes, and then open all the way. Opening the door suddenly can scald a bare hand, arm, or face.
- Wait at least five minutes after opening the door before removing items.
- Large flasks or bottles of liquid removed immediately from the autoclave can cause serious burns by scalding if they break in your hands. Immediately transfer hot items with liquid to a cart; never carry in your hands.
- Wear appropriate PPE, including eye protection and insulating heat-resistant gloves.
Some general safety guidelines to follow when using centrifuges:
- Be familiar with the operating procedures written by the manufacturer. Keep the operating manual near the unit for easy reference. If necessary contact the manufacturer to replace lost manuals.
- Handle, load, clean, and inspect rotors as recommended by the manufacturer.
- Pay careful attention to instructions on balancing samples -- tolerances for balancing are often very restricted and vary according to the type of rotor and speed of centrifugation. Check the condition of tubes and bottles. Make sure you have secured the lid to the rotor and the rotor to the centrifuge.
- Maintain a logbook of rotor use for each rotor, recording the speed and length of time for each use.
- To avoid catastrophic rotor failure, many types of rotors must be "de-rated" (limited to a maximum rotation speed that is less than the maximum rotation speed specified for the rotor when it is new) after a specified amount of use, and eventually taken out of service and discarded.
- Use only the types of rotors that are specifically approved for use in a given centrifuge unit.
- Maintain the centrifuge in good condition. Broken door latches and other problems should be repaired before using the centrifuge.
- Whenever centrifuging biohazardous materials, always load and unload the centrifuge rotor in a biosafety cabinet.
Centrifuge Rotor Care
Basic centrifuge rotor care includes:
- Keeping the rotor clean and dry, to prevent corrosion.
- Removing adapters after use and inspect for corrosion.
- Storing the rotor upside down, in a warm, dry place to prevent condensation in the tubes.
Read and follow the recommendations in the manual regarding:
- Regular cleaning
- Routine inspection
- Regular polishing
- Lubricating O-rings
- Decontaminating the rotor after use with radioactive or biological materials.
Remove any rotor from use that has been dropped or shows any sign of defect, and report it to a manufacturer’s representative for inspection.
A cryogenic gas is a material that is normally a gas at standard temperature and pressure, but which has been supercooled such that it is a liquid or solid at standard pressure. Commonly used cryogenic materials include the liquids nitrogen, argon, and helium, and solid carbon dioxide (dry ice).
Hazards associated with direct personal exposure to cryogenic fluids include:
Frostbite – Liquid and solid cryogenics can cause severe cold contact burns by the liquid, and frostbite or cold exposure by the vapor. Dispensing areas need to be well ventilated. Avoid storing cryogenics in cold rooms, environmental chambers, and other areas with poor ventilation.
Asphyxiation - The ability of the liquid to rapidly convert to large quantities of gas associated with evaporation of cryogenic liquid spills can result in asphyxiation. For instance, nitrogen expands approximately 700 times in volume going from liquid to gas at ambient temperature. Total displacement of oxygen by another gas, such as carbon dioxide, will result in unconsciousness, followed by death. Exposure to oxygen-deficient atmospheres may produce dizziness, nausea, vomiting, loss of consciousness, and death. Such symptoms may occur in seconds without warning. Death may result from errors in judgment, confusion, or loss of consciousness that prevents self-rescue. Working with cryogenic substances in confined spaces, such as walk-in coolers, can be especially hazardous. Where cryogenic materials are used, a hazard assessment is required to determine the potential for an oxygen-deficient condition. Controls such as ventilation and/or gas detection systems may be required to safeguard individuals. If necessary, install an oxygen monitor/oxygen deficiency alarm and/or toxic gas monitor before working these materials in confined areas. Asphyxiation and chemical toxicity are hazards encountered when entering an area that has been used to store cryogenic liquids if proper ventilation/purging techniques are not employed.
Toxicity - Many of the commonly used cryogenic gases are considered to be of low toxicity, but still pose a hazard from asphyxiation. Check the properties of the gases you are using, because some gases are toxic (e.g., carbon monoxide, fluorine, and nitrous oxide). Such gas cylinders should be stored in a well-ventilated area in case of accidental discharge.
Flammability and Explosion Hazards - Fire or explosion may result from the evaporation and vapor buildup of flammable gases such as hydrogen, carbon monoxide, or methane. Liquid oxygen can combine with combustible materials and greatly accelerate combustion. Oxygen clings to clothing and cloth items, and presents an acute fire hazard.
High Pressure Gas Hazards - In cryogenic systems, high pressures are obtained by gas compression during refrigeration, by pumping of liquids to high pressures followed by rapid evaporation, and by confinement of cryogenic fluids with subsequent evaporation. If this confined fluid is suddenly released through a rupture or break in a line, a significant thrust may be experienced. Over-pressurization of cryogenic equipment can occur due to the phase change from liquid to gas if not vented properly. All cryogenic fluids produce large volumes of gas when they vaporize.
Materials and Construction Hazards - The selection of materials that come into contact with cryogenics calls for consideration of the effects of low temperatures on the properties of those materials. Some materials become brittle at low temperatures. Low temperature equipment can also fail due to thermal stresses caused by differential thermal contraction of the materials. Over-pressurization of cryogenic equipment can occur due to the phase change from liquid to gas if not vented properly. All cryogenic fluids produce large volumes of gas when they vaporize.
Cryogenic Safety Guidelines
Personnel who are responsible for any cryogenic equipment must conduct a safety review prior to operating the equipment. Supplementary safety reviews must follow any system modification to ensure that no potentially hazardous condition is overlooked or created and that updated operational and safety procedures remain adequate.
Personal Protective Equipment
Wear the appropriate PPE when working with cryogenic materials. Face shields and splash goggles must be worn during the transfer and normal handling of cryogenic fluids. Loose fitting, heavy leather or other insulating protective gloves must be worn when handling cryogenic fluids. Shirt sleeves should be rolled down and buttoned over glove cuffs, or an equivalent protection such as a lab coat, should be worn in order to prevent liquid from spraying or spilling inside the gloves. Trousers without cuffs should be worn.
Cryogenic fluids must be handled and stored only in containers and systems specifically designed for these products and in accordance with applicable standards, procedures, and proven safe practices.
Transfer operations involving open cryogenic containers such as dewars must be conducted slowly to minimize boiling and splashing of the cryogenic fluid. Transfer of cryogenic fluids from open containers must occur below chest level of the person pouring the liquid.
Only conduct such operations in well-ventilated areas, such as the laboratory, to prevent possible gas or vapor accumulation that may produce an oxygen-deficient atmosphere and lead to asphyxiation. If this is not possible, an oxygen meter must be installed.
Equipment and systems designed for the storage, transfer, and dispensing of cryogenic fluids need to be constructed of materials compatible with the products being handled and the temperatures encountered.
All cryogenic systems including piping must be equipped with pressure relief devices to prevent excessive pressure build-up. Pressure reliefs must be directed to a safe location. It should be noted that two closed valves in a line form a closed system. The vacuum insulation jacket should also be protected by an over pressure device if the service is below 77 Kelvin. In the event a pressure relief device fails, do not attempt to remove the blockage; instead, call EHS at 346-2064.
The caps of liquid nitrogen dewars are designed to fit snugly to contain the liquid nitrogen, but also allow the periodic venting that will occur to prevent an over pressurization of the vessel. Do not ever attempt to seal the caps of liquid nitrogen dewars. Doing so can present a significant hazard of over pressurization that could rupture the container and cause splashes of liquid nitrogen and, depending on the quantity of liquid nitrogen that may get spilled, cause an oxygen deficient atmosphere due to a sudden release and vaporization of the liquid nitrogen.
If liquid nitrogen or helium traps are used to remove condensable gas impurities from a vacuum system that may be closed off by valves, the condensed gases will be released when the trap warms up. Adequate means for relieving resultant build-up of pressure must be provided.
Workers will rarely, if ever, come into contact with cryogenic fluids if proper handling procedures are used. In the unlikely event of contact with a cryogenic liquid or gas, a contact “burn” may occur. The skin or eye tissue will freeze.
If the cryogenic fluid comes in contact with the skin or eyes, flush the affected area with generous quantities of cold water. Never use dry heat. Splashes on bare skin cause a stinging sensation, but, in general, are not harmful.
If clothing becomes soaked with liquid, it should be removed as quickly as possible and the affected area should be flooded with water as above. Where clothing has frozen to the underlying skin, cold water should be poured on the area, but no attempt should be made to remove the clothing until it is completely free.
Seek medical attention immediately if further assistance is needed. Make sure to complete an Injury/Illness Report.
Cryogenic Chemical-Specific Information
Liquid helium must be transferred via helium pressurization in properly designed transfer lines. A major safety hazard may occur if liquid helium comes in contact with air. Air solidifies in contact with liquid helium, and precautions must be taken when transferring liquid helium from one vessel to another or when venting. Over-pressurization and rupture of the container may result. All liquid helium containers must be equipped with a pressure-relief device. The latent heat of vaporization of liquid helium is extremely low (20.5 J/gm); therefore, small heat leaks can cause rapid pressure rises.
Since the boiling point of liquid nitrogen is below that of liquid oxygen, it is possible for oxygen to condense on any surface cooled by liquid nitrogen. If the system is subsequently closed and the liquid nitrogen removed, the evaporation of the condensed oxygen may over-pressurize the equipment or cause a chemical explosion if exposed to combustible materials, e.g., the oil in a rotary vacuum pump. In addition, if the mixture is exposed to radiation, ozone is formed, which freezes out as ice and is very unstable. An explosion can result if this ice is disturbed. For this reason, air should not be admitted to enclosed equipment that is below the boiling point of oxygen unless specifically required by a written procedure.
Any transfer operations involving open containers such as wide-mouth Dewars must be conducted slowly to minimize boiling and splashing of liquid nitrogen. The transfer of liquid nitrogen from open containers must occur below chest level of the person pouring the liquid, so as to avoid vapor contact with the face.
Anyone proposing the use of liquid hydrogen should contact EHS at 541-346-9299 to ensure regulatory and safety concerns have been addressed. Because of its wide flammability range and ease of ignition, special safety measures must be invoked when using liquid hydrogen.
Liquid hydrogen must be transferred by helium pressurization in properly designed transfer lines in order to avoid contact with air. Properly constructed and certified vacuum insulated transfer lines should be used.
Only trained personnel familiar with liquid hydrogen properties, equipment, and operating procedures are permitted to perform transfer operations. Transfer lines in liquid hydrogen service must be purged with helium or gaseous hydrogen, with proper precautions, before using. The safety philosophy in the use of liquid hydrogen can be summarized as the following:
- Isolation of the experiment.
- Provision of adequate ventilation.
- Exclusion of ignition sources plus system grounding/bonding to prevent static charge build-up.
- Containment in helium purged vessels.
- Efficient monitoring for hydrogen leakage.
- Limiting the amount of hydrogen cryopumped in the vacuum system.
EXTRACTIONS AND DISTILLATIONS
- Do not attempt to extract a solution until it is cooler than the boiling point of the extractant due to the risk of over pressurization, which could cause the vessel to burst.
- When a volatile solvent is used, the solution should be swirled and vented repeatedly to reduce pressure before separation. Venting should always take place with the stopcock pointed away from the body.
- When opening the stopcock, your hand should keep the plug firmly in place.
- The stopcock should be lubricated.
- Vent funnels away from ignition sources and people, preferably into a hood.
- Keep volumes small to reduce the risk of overpressure and if large volumes are needed, break them up into smaller batches.
- Avoid bumping (sudden boiling) since the force can break apart the apparatus and result in splashes. Bumping can be avoided by even heating, which can be aided by use of a heat mantle or heating bath. Also, stirring can prevent bumping. Boiling stones can be used only if the process is at atmospheric pressure.
- Do not add solid items such as boiling stones to liquid that is near boiling since it may result in the liquid boiling over spontaneously.
- Organic compounds should never be allowed to boil to dryness unless they are known to be free of peroxides, which can result in an explosion hazard.
Reduced pressure distillation
- Do not overheat the liquid. Superheating can result in decomposition and uncontrolled reactions.
- Superheating and bumping often occur at reduced pressures so it is especially important to abide by the previous point on bumping and to ensure even, controlled heating. Inserting a nitrogen bleed tube may help alleviate this issue.
- Evacuate the assembly gradually to minimize bumping.
- Allow the system to cool and then slowly bleed in air. Air can cause an explosion in a hot system (pure nitrogen is preferable to air for cooling).
- See “reduced pressure” for vacuum conditions.
General Guidelines for use of Glass Under Vacuum
- Inspect glassware that will be used under reduced pressure to make sure there are no defects such as chips or cracks that may compromise its integrity.
- Only glassware that is approved for low pressure should be used. Never use a flat bottom flask (unless it is a heavy walled filter flask) or other thin walled flasks that are not designed to handle low pressure.
- Use a shield between the user and any glass under vacuum or wrap the glass with tape to contain any glass in the event of an implosion
- Hand-blown glassware should not be subjected to vacuum unless it has been appropriately annealed.
- Cold traps should be used to prevent pump oil from being contaminated which can create a hazardous waste.
- Pump exhaust should be vented into a hood when possible.
- Ensure all belts and other moving parts are properly guarded.
- Whenever working on or servicing vacuum pumps, be sure to follow appropriate lock-out procedures.
In most cases laboratory glassware can be cleaned effectively by using detergents and water. In some cases it may be necessary to use strong chemicals for cleaning glassware. Strong acids should be avoided unless necessary. In particular, chromic acid should not be used due to its toxicity and disposal concerns. One product that may be substituted for chromic acid is “Nochromix Reagent”. The Fisher catalog describes this material as: “Nochromix Reagent. Inorganic oxidizer chemically cleans glassware. Contains no metal ions. Rinses freely—leaving no metal residue, making this product valuable for trace analysis, enzymology, and tissue culture work. (Mix with sulfuric acid).” Unused Nochromix Reagent can be neutralized to a pH between 5.5 and 12 and drain disposed. Acid/base baths should have appropriate labeling and secondary containment. Additionally a Standard Operating Procedure (SOP), proper personal protective equipment (PPE), and spill materials should be available. For disposal, spent acid/base bath contents should be neutralized and disposed through the drain.
When handling glassware, check for cracks and chips before washing, autoclaving or use. Dispose of chipped and broken glassware immediately in an approved collection unit. DO NOT put broken glassware in the regular trash. Handle glassware with care – avoid impacts, scratches or intense heating of glassware. Make sure you use the appropriate labware for the procedures and chemicals. Use care when inserting glass tubing into stoppers: use glass tubing that has been fire-polished, lubricate the glass, and protect your hands with heavy gloves.
If your department/building has a glass washing service follow their policies and regulations as to labeling and emptying glassware.
General Guidelines for Setting up Laboratory Apparatus and Equipment
The following recommended laboratory techniques for general equipment set up was taken from the American Chemical Society’s booklet – Safety in Academic Chemistry Laboratories.
Borosilicate glassware (i.e., Pyrex) is recommended for all lab glassware, except for special experiments using UV or other light sources. Soft glass should only be used for things such as reagent bottles, measuring equipment, stirring rods and tubing.
Any glass equipment being evacuated, such as suction flasks, should be specially designed with heavy walls. Dewar flasks and large vacuum vessels should be taped or guarded in case of flying glass from an implosion. Household thermos bottles have thin walls and are not acceptable substitutes for lab Dewar flasks.
Glass containers containing hazardous chemicals should be transported in rubber bottle carriers or buckets to protect them from breakage and contain any spills or leaks. It is recommended to transport plastic containers this way as well since they also can break or leak.
Preparation of Glass Tubing and Stoppers
To cut glass tubing:
- Hold the tube against a firm support and make one firm quick stroke with a sharp triangular file or glass cutter to score the glass long enough to extend approximately one third around the circumference.
- Cover the tubing with cloth and hold the tubing in both hands away from the body. Place thumbs on the tubing opposite the nick 2 to 3 cm and extended toward each other.
- Push out on the tubing with the thumbs as you pull the sections apart, but do not deliberately bend the glass with the hands. If the tubing does not break, re-score the tube in the same place and try again. Be careful to not contact anyone nearby with your motion or with long pieces of tubing.
All glass tubing, including stir rods, should be fire polished before use. Unpolished tubing can cut skin as well as inhibit insertion into stoppers. After polishing or bending glass, give ample time for it to cool before grasping it.
When drilling a stopper:
- Use only a sharp borer one size smaller than that which will just slip over the tube to be inserted. For rubber stoppers, lubricate with water or glycerol. Holes should be bored by slicing through the stopper, twisting with moderate forward pressure, grasping the stopper only with the fingers, and keeping the hand away from the back of the stopper.
- Keep the index finger of the drilling hand against the barrel of the borer and close to the stopper to stop the borer when it breaks through. Preferably, drill only part way through and then finish by drilling from the opposite side.
- Discard a stopper if a hole is irregular or does not fit the inserted tube snugly, if it is cracked, or if it leaks.
- Corks should have been previously softened by rolling and kneading. Rubber or cork stoppers should fit into a joint so that one-third to one–half of the stopper is inserted.
- When available, glassware with ground joints is preferable. Glass stoppers and joints should be clean, dry and lightly lubricated.
Insertion of Glass Tubes or Rods into Stoppers
- The following practices will help prevent accidents:
- Make sure the diameter of the tube or rod is compatible with the diameter of the hose or stopper.
- If not already fire polished, fire polish the end of the glass to be inserted; let it cool.
- Lubricate the glass. Water may be sufficient, but glycerol is a better lubricant.
- Wear heavy gloves or wrap layers of cloth around the glass and protect the other hand by holding the hose or stopper with a layered cloth pad.
- Hold the glass not more than 5 cm from the end to be inserted.
- Insert the glass with a slight twisting motion, avoiding too much pressure and torque.
- When helpful, use a cork borer as a sleeve for insertion of glass tubes.
- If appropriate, substitute a piece of metal tubing for glass tubing.
- Remove stuck tubes by slitting the hose or stopper with a sharp knife
Following these recommendations will help make apparatus assembly easier and equipment safer:
- Keep your work space free of clutter.
- Set up clean, dry apparatus, firmly clamped and well back from the edge of the lab bench making adequate space between your apparatus and others work. Choose sizes that can properly accommodate the operation to be performed. As a rule, leave about 20% free space around your work.
- Use only equipment that is free from flaws such as cracks, chips, frayed wire, and obvious defects. Glassware can be examined in polarized light for strains. Even the smallest crack or chip can render glassware unusable. Cracked or chipped glassware should be repaired or discarded.
- A properly placed pan under a reaction vessel or container will act as secondary containment to confine spilled liquids in the event of glass breakage.
- When working with flammable gases or liquids, do not allow burners or other ignition sources in the vicinity. Use appropriate traps, condensers, or scrubbers to minimize release of material to the environment. If a hot plate is used, ensure the temperatures of all exposed surfaces are less than the autoignition temperature of the chemicals likely to be released and that the temperature control device and the stirring / ventilation motor (if present) do not spark.
- Whenever possible, use controlled electrical heaters or steam in place of gas burners.
- Addition and separatory funnels should be properly supported and oriented so that the stopcock will not be loosened by gravity. A retainer ring should be used on the stopcock plug. Glass stopcocks should be freshly lubricated. Teflon stopcocks should not be lubricated.
- Condensers should be properly supported with securely positioned clamps and the attached water hoses secured with wire or clamps.
- Stirrer motors and vessels should be secured to maintain proper alignment. Magnetic stirring is preferable. Only non-sparking motors should be used in chemical laboratories. Air motors may be an option.
- Apparatus attached to a ring stand should be positioned so that the center of gravity of the system is over the base and not to one side. There should be adequate provision for removing burners or baths quickly. Standards bearing heavy loads should be firmly attached to the bench top. Equipment racks should be securely anchored at the top and bottom.
- Apparatus, equipment, or chemical bottles should not be placed on the floor. If necessary, keep these items under tables and out of aisleways to prevent creating a tripping hazard.
- Never heat a closed container. Provide a vent as part of the apparatus for chemicals that are to be heated. Prior to heating a liquid, place boiling stones in unstirred vessels (except test tubes). If a burner is used, distribute the heat with a ceramic-centered wire gauze. Use the thermometer with its bulb in the boiling liquid if there is the possibility of a dangerous exothermic decomposition as in some distillations. This will provide a warning and may allow time to remove the heat and apply external cooling. The setup should allow for fast removal of heat
- If heating of a closed container is required, only use appropriate pressure-rated thick-walled pressure vessels or equivalent metal pressure reactors. An additional blast shield should be used for safety.
- Whenever hazardous gases or fumes are likely to be evolved, an appropriate gas trap should be used and the operation confined to a fume hood.
- Fume hoods are recommended for all operations in which toxic or flammable vapors are evolved as is the case with many distillations. Most vapors have a density greater than air and will settle on a bench top or floor where they may diffuse to a distant burner or ignition source. These vapors will roll out over astonishingly long distances and, if flammable, an ignition can cause a flash back to the source of vapors. Once diluted with significant amounts of air, vapors move in air essentially as air itself.
- Use a hood when working with a system under reduced pressure (which may implode). Close the sash to provide a shield. If a hood is not available, use a standing shield. Shields that can be knocked over must be stabilized with weights or fasteners. Standing shields are preferably secured near the top. Proper eye and face protection must be worn even when using safety shields or fume hoods.
MERCURY CONTAINING EQUIPMENT
Elemental mercury (Hg) or liquid mercury is commonly seen in thermometers, barometers, diffusion pumps, sphygmomanometers, thermostats, high intensity microscope bulbs, fluorescent bulbs, UV lamps, batteries, Coulter Counter, boilers, ovens, welding machines, etc. Most of these items can be substituted with equipment without mercury, thus greatly decreasing the hazard potential. Larger laboratory equipment may be more difficult to identify as “mercury containing” due to the fact that mercury can be hidden inside inner components such as switches or gauges.
Concerns surrounding mercury containing equipment are:
- It is difficult to identify exposures or cross-contamination due to mercury leaks or spills.
- The amount of mercury used is usually much greater than the Department of Environmental Conservation (DEC) reportable quantities for releases to the environment.
- People may be unaware of the mercury and thus may not be properly trained for use, maintenance, spills, transport or disposal or may not use the appropriate engineering controls or Personal Protective Equipment (PPE).
- There is legal liability if human health and the environment are not properly protected.
To minimize the potential for mercury spills and possible exposures, laboratory personnel are strongly encouraged to follow these recommendations:
- Identify and label “Mercury Containing Equipment”.
- Write a Standard Operating Procedure (SOP) for the use of each piece of equipment containing mercury.
- Train personnel on proper use, maintenance, transport and disposal.
- Conduct periodic inspections of equipment to ensure no leaks or spills have occurred.
- Consider replacing mercury with alternative components. Contact EHS at 346-2348 to replace mercury thermometers with alcohol thermometers of equivalent range.
- Have available proper PPE such as nitrile gloves and post clear warnings to lab personnel that many glove materials do not protect from mercury.
- Use secondary containment, such as trays as a precaution for spills.
- Plan for emergency such as a spill or release of mercury.
- Decontaminate and remove mercury before long-term storage, transport or disposal.
- For new equipment purchases, attempt to procure instruments with no or little mercury.
HYDROFLUORIC ACID (HF) SAFETY PRECAUTIONS
Hydrofluoric acid (HF) has a number of physical, chemical, and toxicological properties that make it especially hazardous. Both anhydrous HF and aqueous solutions are clear, colorless, and highly corrosive liquids. When exposed to air, anhydrous HF and concentrated solutions produce pungent fumes, which are dangerous. HF shares the corrosive properties common to mineral acids, but additionally cause deep tissue damage and systemic toxicity. HF differs from other acids because the fluoride ion readily penetrates the skin, causing destruction of deep tissue layers, including bone. Pain associated with exposure to solutions of HF may be delayed. If HF is not rapidly neutralized and the fluoride ion bound with antidote calcium gluconate, tissue destruction may continue for days and result in limb loss or death.
- Chemical Name: Hydrofluoric Acid
- Synonyms: HF, Hydrofluoride, Fluoric Acid
- Chemical Family: Inorganic Acid.
- Chemical Formula: HF
- Molecular Weight: 20.0
- CAS Number: 7664-39-3
- Physical Data Description: Colorless gas or fuming liquid (below 153°F) with a strong, irritating odor.
- Boiling Point: 153° F (67° C) Specific Gravity: 1.2 (H2O = 1) Vapor Density: 2.21 (Air = 1)
- Vapor pressure: 14 mmHG at 20 C Odor Threshold: 0.5 – 3 ppm (caution: reported range is very broad)
- Fluoride binds to metal-containing enzymes, thereby inactivating them.
- Fluoride binds to calcium, resulting in severe hypocalcemia.
- Fluoride binds to potassium and magnesium ions, leading to myocardial irritability and arrhythmia.
- Fluoride may be directly toxic to the CNS.
Handling and Personal Protective Equipment:
- Familiarize yourself with the hazards specific to HF before handling. Read and understand the Safety Data Sheet (SDS) for HF.
- Always handle HF in a properly functioning fume hood and an area equipped with a safety shower/eyewash.
- Recommended personal protective equipment:
- Goggles (or safety glasses with a plastic face shield)
- Double gloves: Thin disposable gloves (such as 4, 6, or 8 mil blue nitrile glove) used in laboratory operations – these provide a contact barrier only and should be disposed of immediately when contamination is suspected.
- Thicker (10-20 mil) PVC or neoprene gloves provide good resistance to HF but do not provide the necessary dexterity for most lab procedures. Disposable gloves should never be worn without double gloving because of the potential for pinholes and exposure. A combination of double gloves, nitrile and poly, can be used to provide greater protection from a broader range of materials. HF concentrations greater than 30% may not be suitable to handle with nitrile gloves only.
- Acid resistant apron
- Long pants, sleeves, and closed toe shoes (always required when working with corrosives)
HF Exposure Procedures:
- If you get chemical contamination on your skin resulting from an accident, yell for help if someone else is in the lab.
- Immediately go to the nearest emergency shower and pull the activation handle.
- Once under the stream of water, begin removing your clothing to wash off all chemicals.
- Keep flushing for at least 15 minutes or until help arrives. The importance of flushing for at least 15 minutes cannot be overstated! If you spill hydrofluoric acid on yourself, follow the hydrofluoric acid precautions above.
- If you are alone, call 911 after you have finished flushing for at least 15 minutes.
- Seek medical attention.
- Complete a Safety Incident or Accident Report.
If someone else in the lab needs to use an emergency shower (and it is safe for you to do so), assist them to the emergency shower, activate the shower for them, and help them get started flushing using the procedures above; then call 911. After calling 911, go back to assist the person using the shower and continue flushing for 15 minutes or until help arrives and have the person seek medical attention.
NOTE: Although an emergency is no time for modesty, if a person is too modest and reluctant to use the emergency shower, you can provide a barrier/privacy screen using a lab coat or other piece of clothing. If you are assisting someone else, you should wear gloves to avoid contaminating yourself. When using an emergency shower, do not be concerned about the damage from flooding. The important thing to remember is to keep flushing for 15 minutes. If there is a large quantity of chemical spilled or washed off, please contact EHS at 541-346-3912 to see if the rinsate needs to be collected as hazardous waste.