Environmental Health and Safety

Laboratory Safety Manual - 2011

V. Procedures for Specific Classes of Hazardous Chemicals

  1. Flammable Liquids
  2. Oxidizers
  3. Corrosives (Acids and Bases)
  4. Reactives
  5. Compressed Gas Cylinders
  6. Nanomaterials

This section offers specific guidelines for working with common hazardous materials that, for varying reasons, may pose a significant risk to human life and health if used improperly. Six fundamental classes of laboratory chemicals will be discussed; flammables, corrosives, oxidizers, reactives, compressed gases, and nanomaterials. These classes of chemicals may include chemicals that are also covered in the previous section regarding their property of toxicity.

Note that the hazard characteristics of the classes of hazardous chemicals are generalized. Check the MSDS to determine the specific hazard characteristics for the chemical before using it.

1. Flammable Liquids

  1. Terms and Definitions

    Flammable liquids are among the most common chemicals found in a laboratory.  The primary hazard associated with flammable liquids is their ability to readily ignite and burn.  The vapor of a flammable liquid, not the liquid itself, can ignite and start a fire.
  • Vapor pressure - The rate at which a liquid vaporizes.  In general, liquids with high vapor pressure evaporate at a higher rate compared to liquids of lower vapor pressure.  The vapor pressure increases rapidly as the temperature is raised.  A low-pressure environment also accelerates the rate of evaporation.
  • Flash point - The lowest temperature at which a liquid gives off vapor to form an air-vapor mixture that will ignite, but will not sustain ignition.  Many commonly used flammable liquids have flashpoints significantly lower than room temperature:

    Compound Flash Point (°C)
    diethyl ether -45.0
    acetone -17.8
    isopropyl alcohol 11.7
  • Limits of Flammability or Explosivity - The range of fuel:air mixtures that will sustain combustion. The lower limit of this range is called the Lower Explosive Limit (LEL), and the higher limit of this range is called the Upper Explosive Limit (UEL). Materials with very broad flammability ranges (e.g., acetylene, LEL = 3%, UEL = 65%) are particularly dangerous due to the fact that virtually any fuel:air combination may form an explosive atmosphere.
  • Vapor Density of a flammable liquid - The density (mass to volume ratio) of the corresponding vapor relative to air under specific temperature and pressure conditions.  Flammable vapors with densities greater than 1.0 (and thus “heavier” than air) are hazardous because they can accumulate at floor level and spread. These mobile vapors may eventually reach an ignition source, such as an electrical outlet or a Bunsen burner.
  • Autoignition temperature  - The minimum temperature at which a substance can ignite without a spark or flame.  Some examples: acetone 538°C (1000°F), ethyl ether 180°C (356°F), phenol 715°C 91319°F).
  1. Use and Storage of Flammables
  • Flammable liquids that are not in active use should be stored inside fire resistant flammable storage cabinets.
  • Minimize the amount of flammable liquids stored in the lab.  Do not store more than 10 gal outside of flammable storage cabinets.
  • Keep flammables away from vacuum pumps and other ignition sources. 
  • The transfer of material to/from a metal container can result in an accumulation of static charge on the container.  When transferring flammable liquids, this static charge could generate a spark, thereby igniting the liquid.  To make these transfers safer, flammable liquid dispensing and receiving containers should be bonded together before pouring.
  • Large containers such as drums must also be grounded when used as dispensing or receiving vessels. All grounding and bonding connections must be metal to metal.
  • Do not heat flammables with an open flame.  Instead, use steam baths, water baths, oil baths, hot air baths, sand baths or heating mantles.
  • Do not store flammable chemicals in a standard household refrigerator.  There are several ignition sources located inside a standard refrigerator that can cause a fire or explosion.  Flammables that need to refrigeration should be stored cold in a lab-safe explosion-proof refrigerator.

    photo of refrigerator warning label
    Refrigerator warning label

  1. Health Hazards Associated with Flammables
    The vapors of many flammables are irritating to mucous membranes of the respiratory system and eyes. Routes of entry with corresponding symptoms are listed below.

Acute Health Effects

  • Inhalation - headache, fatigue, dizziness, drowsiness, narcosis (stupor and unresponsiveness)
  • Ingestion - slight gastrointestinal irritation, dizziness, fatigue
  • Skin Contact - dry, cracked, and chapped skin
  • Eye Contact - stinging, watering eyes, and inflammation of the eyelids

Chronic Health Effects
The chronic health effects will vary depending on the specific chemical, the duration of the exposure and the extent of the exposure. However, damage to the lungs, liver, kidneys, heart and/or central nervous system may occur. Cancer and reproductive effects are also possible.

Flammable Groups Exhibiting Similar Health Effects

  • Hydrocarbons - aliphatic hydrocarbons are narcotic, but their systemic toxicity is relatively low. Aromatic hydrocarbons are potent narcotic agents, and overexposure to the vapors can lead to loss of muscular coordination, collapse and unconsciousness. Benzene is toxic to bone marrow and can cause leukemia.
  • Alcohols - vapors can be moderately narcotic.
  • Ethers - exhibit strong narcotic properties and can be moderately toxic.
  • Esters - vapors may result in irritation to the eyes, nose and upper respiratory tract.
  • Ketones - systemic toxicity is generally low.
  1. First Aid Procedures for Exposures to Flammable Materials
  • Inhalation Exposures - remove the person from the contaminated area.  Get medical attention.
  • Ingestion Exposures - Get medical attention.
  • Dermal Exposures - remove the person from the source of contamination. Remove clothing and jewelry from the affected areas. Rinse in a safety shower for at least 15 minutes and obtain medical attention.
  • Eye Contact - remove the person from the source of contamination. Flush with an eyewash for at least 15 minutes and obtain medical attention.
  1. Personal Protective Equipment (PPE)
    Fume hoods should be used when working with flammable liquids. Nitrile and neoprene gloves provide protection against most flammables. Wear a fire-resistant lab coat to provide a barrier to your skin. Safety goggles/glasses should be worn if there is a splash risk.

    photo of proper PPE
    Proper PPE

2. Oxidizers

  1. General Characteristics
  • Oxidizers present fire and explosion hazards on contact with flammable and combustible materials. Depending on the class, an oxidizing material may increase the burning rate of combustibles which it contacts; cause the spontaneous ignition of combustibles which it contacts, or produce an explosive reaction when exposed to heat, shock or friction.
  • Oxidizers are generally corrosive.
  1. Examples of Common Oxidizers

Peroxides
Nitrates
Nitrites
Perchlorates

Chlorates
Chlorites
Hypochlorites
Dichromates


  1. Use and Storage of Oxidizers
  • Store oxidizers away from flammables, organic compounds and combustible materials.
  • Strong oxidizing agents like chromic acid should be stored in glass or some other inert container.  Corks and rubber stoppers should not be used.
  • Reaction vessels containing oxidizing material should be heated in a mantle or sand bath.  Oil baths should not be used.
  1. Use and Storage of Perchloric Acid
  • Perchloric acid is an oxidizing agent of particular concern.  The oxidizing power of perchloric acid increases as the concentration and temperature increase. Cold, 70% perchloric acid is a strong, non-oxidizing corrosive.  A 72% perchloric acid solution at elevated temperatures is a strong oxidizing agent.  An 85% perchloric acid solution is a strong oxidizer at room temperature.
  • Do not attempt to heat perchloric acid if you do not have access to a properly functioning perchloric acid fume hood. Perchloric acid can only be heated in a hood specially equipped with a washdown system to remove any perchloric acid residue. The hood should be washed down after each use, and it is preferred that the hood be restricted to perchloric acid use only.
  • Whenever possible, substitute a less hazardous chemical for perchloric acid or use a dilute solution.
  • Perchloric acid can be stored in a perchloric acid fume hood. Keep only the minimum amount necessary for your work.  Another acceptable storage site for perchloric acid is in an acid cabinet that has secondary containment.
  • Do not allow perchloric acid to come in contact with any strong dehydrating agents such as sulfuric acid.  The dehydration of perchloric acid is a severe fire and explosion hazard.
  • Do not order or use anhydrous perchloric acid.  It is unstable at room temperature and can decompose spontaneously with a severe explosion. Anhydrous perchloric acid will explode upon contact with wood.
  • Consult with EHS before working with perchloric acid.
  1. Health Hazards Associated with Oxidizers
    Acute Health Effects:

    Some oxidizers such as nitric and sulfuric acid vapors, chlorine, and hydrogen peroxide
    act as irritant gases.  All irritant gases can cause inflammation in the surface layer of
    tissues when in direct contact.  They can also cause irritation of the upper airways,
    conjunctiva, and throat.
  • Fluorine, can cause severe burns of the skin and mucus membranes.  
  • Chlorine trifluoride is extremely toxic and can cause severe burns to tissue.
  • Nitrogen trioxide is very damaging to tissue, especially the respiratory tract.  The symptoms from an exposure to nitrogen trioxide may be delayed for hours, but fatal pulmonary edema may result.
  • Osmium tetroxide also dangerous due to its high degree of acute toxicity. It is a severe irritant of the eyes and respiratory tract. Inhalation can cause headache, coughing, dizziness, lung damage, difficulty breathing and death. Osmium tetroxide is regarded by many in the field as having "poor warning properties." This is due to the fact that it is difficult to detect in the atmosphere (by smell or other means). The OSHA Permissible Exposure Limit (PEL) for osmium tetroxide is 0.002 ppm, while its odor threshold is 2 ppm -this means that one could conceivably be exposed to osmium tetroxide at concentrations 1,000 times the PEL without knowing it.  It is recommended that laboratories using osmium tetroxide have necessary safeguards in place before the container is even opened.

Chronic Health Effects:
Nitrobenzene and chromium compounds can cause hematological and neurological changes. Compounds of chromium and manganese can cause liver and kidney disease.  Chromium (VI) compounds have been associated with lung cancer.

  1. First Aid
    If a person has inhaled, ingested or come into direct contact with these materials, the person should be removed from the immediate area as quickly as possible. Seek medical attention immediately.  Rinse with a safety shower for at least 15 minutes if there is direct skin exposure.  Flush with an eyewash for at least 15 minutes if there is direct eye exposure.
  2. Personal Protective Equipment (PPE)
    Neoprene, polyvinyl chloride (PVC), or nitrile gloves are acceptable.  Consult a glove compatibility chart to ensure the glove material is appropriate for the particular chemical you are using.

    Safety glasses must be worn if the potential for splashing or exposure to vapor/gas exists.

    Oxidizers should be used in a chemical fume hood due to the inhalation hazard risk.

3. Corrosives (Acids and Bases)

  1. General Characteristics
  • Corrosives are most commonly acids and bases, but many other materials can be severely damaging to living tissue.
  • Corrosives can damage tissue.  Inhalation of the vapor or mist can cause severe bronchial irritation. Corrosives are particularly damaging to the skin and eyes.
  • Certain substances considered non-corrosive in their natural dry state are corrosive when they come in contact with moist skin or mucus membranes. Examples include lithium chloride, halogen fluorides, and allyl iodide.
  • Sulfuric acid is a very strong dehydrating agent while nitric acid is a strong oxidizing agent. Dehydrating agents can cause severe burns to the eyes due to their affinity for water.
  1. Examples of Corrosives

Sulfuric Acid
Ammonium Hydroxide

Chromic Acid

Bromine


  1. Use and Storage of Corrosives
  • Always store acids and bases separately.  Store acids in acid storage cabinets or plastic secondary containment away from flammables as many acids are also strong oxidizers.

    photo of acid storage cabinet
    Acids stored in acid storage cabinet

  • Do not work with corrosives unless an emergency shower and eyewash are available within 10 sec travel time.   Contact EHS if one is not available.
  • Add acid to water, but never add water to acid.  
  • Do not store liquid acids above eye level.  Store on a low shelf or inside a cabinet.
  • Store acids in a plastic tray, tub or rubber bucket to contain any leakage.

    photo of acid storage tray
    Acids stored in a plastic tray

  • Purchase corrosives in containers that are plastic coated, this will reduce the danger to personnel if the container is dropped.
  • Store acids in an acid cabinet or one that has a corrosion-resistant lining.  Acids stored in an ordinary metal cabinet will quickly corrode the interior.  If an acid cabinet is not available, store the corrosive in a plastic tub inside a wooden cabinet.
  • Nitric acid should always be stored away from other acids and organic materials in a separate cabinet or compartment due to its high reactivity.
  1. Use and Storage of Hydrofluoric Acid
  • Hydrofluoric acid can cause severe burns. Inhalation of anhydrous hydrogen fluoride can be fatal. Initial skin contact with hydrofluoric acid may not produce any symptoms. However, hydrofluoric acid can scavenge calcium for the skin and bones, causing severe injuries.
  • Always use hydrofluoric acid in a properly functioning fume hood. Wear personal protective clothing.
  • If you suspect that you have come in direct contact with hydrofluoric acid; wash the area with water for at least 5 minutes, then apply cream.  Remove contaminated clothing and seek medical attention.  If hydrogen fluoride vapors are inhaled, move the person immediately to an uncontaminated atmosphere (if safe to do so) and seek prompt medical attention.
  • Never store hydrofluoric acid in a glass container as it is incompatible with glass. Hydrofluoric acid usually comes in a plastic bottle.
  • Store hydrofluoric acid separately in an acid storage cabinet and keep only the amount necessary in the lab.
  • Creams such as calcium gluconate for treatment of hydrofluoric acid exposure are commercially available and should be stored in the lab. Calcium gluconate reacts with hydrofluoric acid reducing attack of calcium in the body.

Health Hazards Associated with Corrosives
All corrosives possess the property of being severely damaging to living tissues.  Acids also react with other materials such as metals.

Skin contact with alkali metal hydroxides (e.g., sodium hydroxide and potassium hydroxide) is more dangerous than with strong acids. Contact with base metal hydroxides normally causes deeper tissue damage because there is less pain than with an acid exposure. The exposed person may not wash it off thoroughly enough or seek prompt medical attention.

All hydrogen halides are acids that are serious respiratory irritants and also cause severe burns.

Acute Health Effects

  • Inhalation - irritation of mucus membranes, difficulty in breathing, fits of coughing, pulmonary edema Ingestion - irritation and burning sensation of lips, mouth, and throat; pain in swallowing; swelling of the throat; painful abdominal cramps; vomiting; shock; risk of perforation of the stomach.
  • Skin Contact - burning, redness and swelling, painful blisters, profound damage to tissues, and with alkalis; a slippery, soapy feeling.
  • Eye Contact - stinging, watering of eyes, swelling of eyelids, intense pain, ulceration of eyes, loss of eyes or eyesight.

Chronic Health Effects
Symptoms associated with a chronic exposure vary greatly depending on the chemical. For example, the chronic effect of hydrochloric acid is damage to the teeth; the chronic effects of hydrofluoric acid are decreased bone density, fluorosis, and anemia.

  1. First Aid
  • Inhalation - remove person from source of contamination if safe to do so. Seek medical attention.
  • Ingestion - remove person from source of contamination. Seek medical attention and inform emergency responders of the name of the chemical swallowed.
  • Skin Contact - remove person from source of contamination and take immediately to an emergency shower or source of water. Remove clothing, shoes, socks, and jewelry from affected areas as quickly as possible, cutting them off if necessary. Be careful not to get any chemical on your skin or to inhale the vapors. Flush the affected area with water for a minimum of 15 minutes. Get medical attention.
  • Eye Contact - remove person from source of contamination and take immediately to an eyewash or source of water. Rinse the eyes for a minimum of 15 minutes. Have the person look up and down and from side to side. Get medical attention. Do not let the person rub their eyes or keep them tightly shut.
  1. Personal Protective Equipment (PPE)
    Always wear the proper gloves when working with corrosives. Neoprene and nitrile gloves are effective against most acids and bases. Polyvinyl chloride (PVC) is also effective for most acids. A rubber coated apron and goggles should also be worn. If splashing is likely to occur, wear a face shield over the goggles. Always use corrosives in a chemical fume hood.

4. Reactives

  1. General Characteristics
    Polymerization Reactions
    Polymerization is a chemical reaction in which two or more molecules of a substance combine to form repeating structural units of the original molecule.  This can result in an extremely high or uncontrolled release of heat. An example of a chemical which can undergo a polymerization reaction is styrene.

Water Reactive Materials

  • When water reactive materials come in contact with water, one or more of the following can occur: liberation of heat which may cause ignition of the chemical itself if it is flammable, or ignition of flammables that are stored nearby; release of a flammable, toxic, or strong oxidizing gas; release of metal oxide fumes; and formation of corrosive acids.
  • Water reactive chemicals can be particularly hazardous to firefighting personnel responding to a fire in a lab, because water is the most commonly used fire extinguishing medium.
  • Examples of water reactive materials:

Alkali Metals:
 -Lithium, Sodium, Potassium
Magnesium
Aluminum

Silanes
Alkylaluminums
Zinc


Pyrophorics

  • Pyrophoric materials can ignite spontaneously in the presence of air.
  • Examples of pyrophoric materials:

Tert-butyllithium
Diethylzinc
Triethylaluminum
Several organometallic compounds

Peroxide-Forming Materials

  • Peroxides are very unstable and some chemicals that can form them are commonly used in laboratories. This makes peroxide-forming materials some of the most hazardous substances found in a lab. Peroxide-forming materials are chemicals that react with air, moisture, or impurities to form peroxides. The tendency to form peroxides by most of these materials is greatly increased by evaporation or distillation.
  • Organic peroxides are extremely sensitive to shock, sparks, heat, friction, impact, and light. Many peroxides formed from materials used in laboratories are more shock sensitive than TNT. Just the friction from unscrewing the cap of a container of ether that has peroxides in it can provide enough energy to cause a severe explosion.
  • Examples of peroxide-forming materials (the italicized group is the more hazardous):

Diisopropyl Ether
Sodium Amide
Dioxane
Tetrahydrofuran
Butadiene
Acrylonitrile

Divinylacetylene
Potassium Amide
Diethyl Ether 
Vinyl Ethers
Vinylpyridine
Styrene


Peroxide Testing
For certain classes of compounds (e.g., ethers as peroxide formers), the date the container was opened should be written on the label. Peroxide formers should have the test history and date of discard written on the label as well.

The following tests can detect most (but not all) peroxy compounds, including all hydroperoxides:

-Add 1 to 3 milliliters (mL) of the liquid to be tested to an equal volume of acetic acid, add a few drops of 5% aqueous potassium iodide solution, and shake.  The appearance of a yellow to brown color indicates the presence of peroxides. Alternatively, addition of 1 mL of a freshly prepared 10% solution of potassium iodide to 10 mL of an organic liquid in a 25-mL glass cylinder should produce a yellow color if peroxides are present.

-Add 0.5 mL of the liquid to be tested to a mixture of 1 mL of 10% aqueous potassium iodide solution and 0.5 mL of dilute hydrochloric acid to which has been added a few drops of starch solution just prior to the test. The appearance of a blue or blue-black color within a minute indicates the presence of peroxides.

-Peroxide test strips, which turn to an indicative color in the presence of peroxides, are available commercially.  Note that these strips must be air dried until the solvent evaporates and then exposed to moisture for proper operation.

None of these tests should be applied to materials (such as metallic potassium) that may be contaminated with inorganic peroxides.

Note: Peroxide test strips are available through the chemical storeroom in Welch.

Other Shock-Sensitive Materials

  • These materials are explosive and sensitive to heat and shock.
  • Examples of shock-sensitive materials:

Chemicals containing nitro-functional groups
Fulminates
Hydrogen Peroxide (30% +)
Ammonium Perchlorate
Benzoyl Peroxide (when dry)
Compounds containing the functional groups: acetylide, azide, diazo, halamine, nitroso, and ozonide.

  1. Use and Storage of Reactives
  • A good way to reduce the potential risks is to minimize the amount of material used in the project. Use only the amount of material necessary to achieve the desired results.
  • Always substitute a less hazardous chemical for a highly reactive chemical whenever possible. If it is necessary to use a highly reactive chemical, order only the amount that is necessary for the work.

Water Reactive Materials
Store water-reactive chemicals in an isolated part of the lab. A cabinet removed from water sources, such as sinks, emergency showers, and chillers, is an appropriate location.  Clearly label the cabinet "Water-Reactive Chemicals – No Water".

Pyrophorics
Store pyrophorics in an isolated part of the lab and in a clearly marked cabinet. Be sure to routinely check the integrity of the container and have the material disposed of through EHS if the container is corroded or otherwise damaged.

Additional safety guidance on pyrophorics can be found at: http://www.utexas.edu/safety/ehs/lab/pyrophorics.html

Peroxide-Forming Materials

  • Do not open the chemical container if peroxide formation is suspected. The act of opening the container could be sufficient to cause a severe explosion. Visually inspect liquid peroxide-forming materials for crystals or unusual viscosity before opening. Pay special attention to the area around the cap. Peroxides usually form upon evaporation, so they will most likely be formed on the threads under the cap.
  • Date all peroxide forming materials with the date received.  Chemicals such as diisopropyl ether, divinyl acetylene, sodium amide, and vinylidene chloride should be discarded after three months. Chemicals such as dioxane, diethyl ether, and tetrahydrofuran should be submitted to EHS for disposal after one year if opened or expired.
  • Store all peroxide-forming materials away from heat, light, and sources of ignition. Light accelerates the formation of peroxides.
  • Secure the lids and caps on these containers to discourage the evaporation and concentration of these chemicals.
  • Never store peroxide-forming materials in glass containers with screw cap lids or glass stoppers. Friction and grinding must be avoided.
  • From Prudent Practices in the Laboratory – Handling and Disposing of Chemicals – 1995 – Page 100 – Section 5.G.3.1 Peroxide Detection Tests|
    The following tests can detect most (but not all) peroxy compounds, including all hydroperoxides:
    • Add 1 to 3 milliliters (mL) of the liquid to be tested to an equal volume of acetic acid, add a few drops of 5% aqueous potassium iodide solution, and shake.  The appearance of a yellow to brown color indicates the presence of peroxides. Alternatively, addition of 1 mL of a freshly prepared 10% solution of potassium iodide to 10 mL of an organic liquid in a 25-mL glass cylinder should produce a yellow color if peroxides are present.
    • Add 0.5 mL of the liquid to be tested to a mixture of 1 mL of 10% aqueous potassium iodide solution and 0.5 mL of dilute hydrochloric acid to which has been added a few drops of starch solution just prior to the test. The appearance of a blue or blue-black color within a minute indicates the presence of peroxides.
    • Peroxide test strips, which turn to an indicative color in the presence of peroxides, are available commercially.  Note that these strips must be air dried until the solvent evaporates and then exposed to moisture for proper operation.
    • None of these tests should be applied to materials (such as metallic potassium) that may be contaminated with inorganic peroxides.
  • If you suspect that peroxides may be present contact EHS.  If you notice crystal formation in the container or around the cap, do not attempt to open or move the container. Call EHS for proper disposal.
  • Never distill ether unless it is known to be free of peroxides.

    photo of chemical containers in poor condition
    Chemical containers in poor condition from corrosion and crystal formation

Other Shock Sensitive Materials
Store these materials separately from other chemicals and in a clearly labeled
cabinet. 

Never allow picric acid (Bouin’s solution) to dry out, as it is extremely explosive. Always store picric acid in a moist environment.  

  1. Health Hazards Associated with Reactives
    Reactive chemicals are grouped as a category primarily because of the safety hazards associated with their use and storage and not because of similar acute or chronic health effects. For health hazard information on specific reactive materials consult the MSDS, the manufacturer, or EHS. However, there are some hazards common to the use of reactive materials. Injuries can occur due to: heat or flames, inhalation of fumes, vapors, reaction products, and flying debris.

    First Aid
    If someone is seriously injured, the most important step to take is to contact emergency responders as quickly as possible.  Explain the situation and describe the location clearly and accurately.

    If someone is severely bleeding, put on protective gloves and apply a sterile dressing, clean cloth, or handkerchief to the wound. Then place the palm of your hand directly over the wound and apply pressure and keep the person calm. Continue to apply pressure until help arrives.

    If a person's clothes are on fire, he or she should drop immediately to the floor and roll. If a fire blanket is available, put it over the individual. An emergency shower, if one is immediately available, can also be used to douse flames.

    If a person goes into shock, have the individual lie down on their back (if safe to do so) and raise the feet about one foot above the floor.

    Personal Protective Equipment (PPE)
    Wear appropriate personal protective clothing while working with highly reactive materials. This might include: impact resistant safety glasses or goggles, a face shield, gloves, a flame-resistant lab coat (to minimize injuries from flying glass or an explosive flash), and a blast shield. Conduct work within a chemical fume hood as much as possible and pull down the sash as far as is practical. While the project does not require you to reach into the fume hood, keep the sash closed.

    Barriers can offer protection of personnel against explosions and should be used. Many safety catalogs offer commercial shields which are commonly polycarbonate and are weighted at the bottom for stability. It may be necessary to secure the shields firmly to the work surface.

5. Compressed Gas Cylinders

  1. General Characteristics
  • Cylinders of compressed gases can pose a chemical as well as a physical hazard.
  • If the valve were to break off a cylinder, the amount of force present could propel the cylinder through a brick wall. For example, a cylinder of compressed breathing air used by SCUBA divers has the explosive force of 1 1/2 pounds of TNT.
  1. Purchase Policy
    Purchase of gases in non-returnable cylinders is restricted by policy at UT Austin.  The UT Austin Gas Cylinder policy, which went into effect in May 1993, requires that all gas cylinders purchased for use on campus must be returnable to the vendor. The only exception to this policy is for a compelling research reason. The original policy indicated such exceptions would require prior approval and that a $1,000 deposit would be required to cover potential disposal costs. The specific procedures to be followed to request permission to purchase a research gas in a non-returnable gas cylinder are outlined below.

    The Principal Investigator (PI) should prepare a request for an exception and include the reason why a non-returnable gas cylinder purchase is essential. This request must contain a Letter of Credit commitment that specifically states the requesting PI will be responsible for the proper disposal of the non-returnable cylinder and agrees to pay a $1,000 disposal fee if UT Austin is required to dispose of the cylinder. This request should be submitted to the department chair and the dean for review and approval. The request should then be forwarded to the Provost for final action. Please note: identification of a specific account or funding source by the PI for the possible $1,000 disposal expenditure is not required but approval by the department and the college constitutes a commitment by them that department or college funds are available to cover disposal costs if the PI is unable to cover these costs.

    A copy of the approval request will be returned to the PI and a copy will be forwarded to EHS. The PI should attach a copy of the approved request to the purchase order used to obtain the desired gas.

    Final disposal of the non-returnable gas cylinder should be completed no later than three years after purchase unless written approval for an extension is obtained from the Provost upon recommendation of the chair and dean. Evidence of the proper disposal of the cylinder must be provided to EHS. If the cylinder is disposed of through normal channels (e.g. the EHS Hazardous Waste Program) at no extra cost to UT Austin, the $1,000 Letter of Credit commitment will be canceled. The cylinder will be acceptable for normal waste disposal if the valve has been removed from the cylinder and the cylinder has been cleaned. Similarly, if the cylinder has been returned to the manufacturer or distributor, and this is verified in the form of a receipt or a bill of lading, the Letter of Credit commitment will be canceled. If however, the university must dispose of the cylinder outside of normal procedures because of the cylinder's condition (e.g. damaged or corroded valve) the disposal fee of $1,000 will be assessed to the PI. It is the responsibility of the PI to provide an appropriate account for this charge at that time.
  2. Use and Storage
  • Whenever possible, use flammable and reactive gases in a fume hood or other ventilated enclosure. As noted previously, concerning storage cabinets, certain categories of toxic gases must always be stored and used in ventilated enclosures. Note specific gases that require ventilated storage.
  • Always use the appropriate regulator on a cylinder. If a regulator will not fit a cylinder's valve, replace the cylinder, not the regulator. Do not attempt to adapt or modify a regulator to fit a cylinder it was not designed for. Regulators are designed to fit only specific cylinder valves to avoid improper use.

    photo of properly attached regulator and safety cap
    Properly attached regulator and safety cap

  • Inspect regulators, pressure relief devices, valves, cylinder connections, and hose lines frequently for damage.
  • Do not use a cylinder that cannot be positively identified. Color coding is not a reliable way of identifying a cylinder because the colors can vary from supplier to supplier.
  • Do not use oil or grease on any cylinder component because a fire or explosion can result.
  • Do not transfer gases from one cylinder to another.  The gas may be incompatible with the residual gas remaining in the cylinder or may be incompatible with the cylinder material.
  • Never completely empty cylinders during lab operations
    • Leave approximately 25 PSI of pressure. This will prevent any residual gas in the cylinder from becoming contaminated. However, if the cylinder is non-returnable, call EHS for instructions. If inert, vent the remainder of the gas. If not inert, react the remainder of gas off. In either case, EHS will be able to discard the cylinder after valve removal. If venting or reacting is unsafe, EHS can still dispose of most cylinders.
  • Orient cylinders so that the main valve is always accessible and the name of the gas is visible.
  • Close the main cylinder valve whenever the cylinder is not in use.
  • Remove regulators from unused cylinders and always put the safety cap in place to protect the valve.
  • Always secure cylinders, whether empty or full, to prevent them from falling over and damaging the valve (or falling on your foot).  Secure cylinders by firmly chaining or strapping them to a wall, lab bench, or other fixed support.

    photo of compressed gas cylinders
    Compressed gas cylinders (Picture courtesy of Airgas, Inc.)

  • Oxygen should be stored in an area that is at least 20 feet away from any flammable or combustible materials (including gasses) or separated from combustibles by a non-combustible barrier at least 5 feet high and having a fire-resistance rating of at least 1/2 hour.
  • To transport a cylinder, put on the safety cap and strap the cylinder to a hand truck in an upright position. Never roll a cylinder.

    photo of proper transport of a gas cylinder
    Proper transport of a gas cylinder
    (Picture courtesy of Airgas, Inc.)

  • Always clearly mark empty cylinders and store them separately.
  • Be careful while handling compressed gas cylinders and never drop or strike a cylinder against anything.
  • Use only wrenches or other tools supplied by the cylinder supplier to open a valve. 
  • Open cylinder valves slowly.
  • Only compatible gases should be stored together in a gas cylinder cabinet.
  • Do not store compressed gas cylinders in areas where the temperature can exceed 125F.

6. Nanomaterials (UNDER DEVELOPMENT)

Guidance regarding the safe use of nanomaterials is under development. Contact EHS Lab Safety for assistance.