Cryogenic safety involves protecting employees from the hazards created by extremely cold liquids, gases, equipment, and surfaces. Cryogenic liquids are widely used in laboratories for cooling, freezing, sample preservation, cold traps, research, medical applications, and other processes.
Common laboratory cryogens include liquid nitrogen, liquid helium, liquid argon, liquid oxygen, and liquid hydrogen. Although their individual properties differ, cryogenic materials can present serious hazards from extreme cold, rapid expansion, pressure buildup, oxygen displacement, oxygen enrichment, fire, and chemical reactivity.
OSHA’s Laboratory Safety Guidance describes cryogens as substances used to produce very low temperatures—generally below −153°C (−243°F). Liquid nitrogen, one of the most commonly used laboratory cryogens, boils at approximately −196°C (−321°F).
Safe cryogenic work requires more than simply wearing insulated gloves. The laboratory should evaluate the material, quantity, container, ventilation, room size, transfer method, pressure-relief system, PPE, and potential consequences of a spill or equipment failure.
What Are Cryogenic Liquids?
A cryogenic liquid is a liquefied gas maintained at an extremely low temperature.
Examples include:
Liquid Nitrogen (LN₂) – Commonly used for freezing, cooling, sample preservation, and laboratory equipment.
Liquid Helium (LHe) – Used in specialized research, superconducting magnets, and other extremely low-temperature applications.
Liquid Argon (LAr) – Used in research, analytical applications, and other specialized processes.
Liquid Oxygen (LOX) – An extremely cold liquid that also presents a significant oxidizing and fire hazard.
Liquid Hydrogen (LH₂) – Presents both cryogenic hazards and an extremely significant flammability hazard.
Each cryogen has unique physical and chemical properties. Employees should review the applicable Safety Data Sheet (SDS) and operating procedures before use.
Cryogenic Safety Hazards
OSHA identifies four principal safety hazards associated with cryogenic liquids:
Cold-contact burns
Asphyxiation
Pressure explosion
Chemical explosion or reaction
These hazards can occur independently or simultaneously.
Extreme Cold and Cryogenic Burns
Contact with a cryogenic liquid, cold vapor, or cryogenically cooled surface can cause severe tissue damage.
The injury may resemble a thermal burn but results from extreme cold.
Exposure can cause:
- Frostbite.
- Cold burns.
- Tissue damage.
- Eye injury.
- Skin adhering to cold surfaces.
Even brief contact may cause injury.
Cryogenic liquid can also become trapped against the body by:
- Gloves.
- Shoes.
- Jewelry.
- Watches.
- Clothing.
- Cuffs or pockets.
For this reason, PPE should be selected and worn so spilled cryogenic liquid can shed away from the body rather than becoming trapped against the skin.
Never Touch Cryogenic Equipment With Bare Skin
Metal, glass, tubing, valves, transfer lines, and other surfaces associated with cryogenic systems may remain dangerously cold even when no liquid is visible.
Bare skin can freeze to extremely cold surfaces.
Do not assume equipment is safe to touch simply because frost is not visible.
Use appropriate gloves or handling tools when contact with cold equipment is necessary.
Oxygen-Deficiency Hazards
One of the most serious hazards associated with cryogenic liquids such as nitrogen, helium, and argon is oxygen displacement.
As a cryogenic liquid warms, it vaporizes and expands into a much larger volume of gas.
In a poorly ventilated room or enclosed area, the expanding gas can displace normal atmospheric oxygen and create an oxygen-deficient atmosphere.
The gas may be:
- Colorless.
- Odorless.
- Tasteless.
- Difficult or impossible for employees to detect without instrumentation.
A person may therefore enter a hazardous atmosphere without realizing oxygen has been displaced.
OSHA has investigated fatal incidents involving liquid nitrogen where inadequate ventilation and oxygen monitoring allowed nitrogen gas to create an oxygen-deficient atmosphere.
Liquid Nitrogen and Asphyxiation
Liquid nitrogen deserves particular attention because it is so widely used and may appear relatively harmless.
Nitrogen itself is not poisonous in the conventional sense. The danger is that a sufficient release can displace the oxygen needed to breathe.
This can occur following:
- A liquid nitrogen spill.
- A leaking Dewar.
- Transfer-line failure.
- Pressure-relief discharge.
- Equipment failure.
- Filling operations.
- Boil-off from stored material.
- Loss of vacuum insulation.
- Large quantities stored in a small room.
An employee should never enter a suspected oxygen-deficient area to rescue another person without appropriate training and equipment.
Unprotected rescuers can become additional victims. OSHA accident records include incidents in which people attempting to help workers overcome by nitrogen entered the same deficient atmosphere and were also killed.
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Ventilation for Cryogenic Liquids
Rooms where cryogenic liquids are stored, transferred, or used should have ventilation appropriate to the potential release.
A cryogenic hazard assessment should consider:
What cryogen is present?
How much is present?
What is the room volume?
What is the normal ventilation rate?
What happens if the entire container releases?
Where will the gas accumulate?
Is cryogen routinely transferred or dispensed?
Could ventilation fail?
Are there adjacent enclosed or low-lying spaces?
A large quantity of liquid nitrogen used in a small enclosed room presents a very different risk than a small quantity used in a large, well-ventilated laboratory.
OSHA has specifically cited inadequate ventilation and lack of oxygen monitoring in workplaces where liquid nitrogen dispensing created recognized oxygen-deficiency hazards.
Never Enter an Area With an Oxygen Alarm
If an oxygen-deficiency alarm activates:
Stop and do not enter the affected area.
If already inside and evacuation is required:
Leave immediately according to established emergency procedures.
Do not enter or reenter the area to:
- Retrieve equipment.
- Close a valve or stop a leak.
- Investigate the cause of the alarm.
- Rescue a coworker.
An oxygen-deficiency alarm may indicate an atmosphere that is immediately dangerous to life or health (IDLH). Entry or rescue must be performed only by personnel specifically trained, equipped, and authorized to enter the hazardous atmosphere in accordance with the applicable emergency-response and respiratory-protection procedures.
Never attempt an unprotected rescue. An unconscious or incapacitated person inside the area may be evidence of a hazardous atmosphere. Entering without proper protection can result in additional victims.
Rapid Expansion of Cryogenic Liquids
Cryogenic liquids expand dramatically when they warm and convert to gas.
This creates two major concerns:
Oxygen displacement
and
Pressure buildup
A small volume of cryogenic liquid can produce a much larger volume of gas.
For this reason, cryogenic liquids should never be placed in an ordinary sealed container.
The expanding gas must have a safe means of escape.
Pressure Buildup
Heat continually enters cryogenic containers from the surrounding environment.
As the cryogenic liquid warms, some of it vaporizes.
If the resulting gas cannot escape, pressure can increase until the container, transfer line, or another system component fails.
OSHA’s laboratory guidance specifically identifies pressure explosion as a cryogenic hazard and states that adequate pressure relief should be provided to all parts of a cryogenic system to permit routine outgassing and prevent dangerous pressure buildup.
Never Seal a Cryogenic Liquid in an Unvented Container
A container holding cryogenic liquid should never be sealed unless it is specifically designed for that service with appropriate pressure controls and relief systems.
Do not improvise by:
- Tightening an inappropriate cap.
- Plugging a vent.
- Blocking a pressure-relief device.
- Sealing a Dewar with an ordinary stopper.
- Closing valves that trap cryogenic liquid between them without appropriate pressure relief.
Trapped cryogenic liquid can warm, expand, and create dangerous pressure.
Trapped-Liquid Hazards
Cryogenic liquid can become trapped between:
- Closed valves.
- Plugs.
- Caps.
- Check valves.
- Sections of piping.
- Other isolated system components.
As the liquid warms and expands, extremely high pressure can develop.
Cryogenic systems should therefore be designed so that any location where liquid can become trapped has an appropriate means of pressure relief.
Pressure-relief devices should not be:
- Removed.
- Plugged.
- Blocked.
- Painted shut.
- Altered.
- Defeated.
System modifications should be evaluated by qualified personnel.
Dewars and Cryogenic Containers
Cryogenic liquids should be stored only in containers designed for cryogenic service.
Common containers include:
- Dewar flasks.
- Cryogenic storage vessels.
- Vacuum-insulated containers.
- Specialized cryogenic freezers.
Containers should be compatible with the cryogen and the pressure conditions involved.
Inspect containers and associated equipment for:
- Physical damage.
- Excessive frost or ice.
- Damaged necks.
- Leaks.
- Unusual venting.
- Defective valves.
- Damaged pressure-relief devices.
- Loss of vacuum.
- Unusual pressure.
- Deteriorating hoses or transfer lines.
Do not continue using equipment that appears damaged or is behaving abnormally.
Excessive Frost and Ice
Some frost is expected around certain cryogenic operations, but unusual or excessive frost can indicate a problem.
It may suggest:
- Loss of vacuum insulation.
- Leakage.
- Valve problems.
- Damaged transfer equipment.
- Abnormal boil-off.
Unexpected changes in frost patterns, venting, pressure, or cryogen consumption should be investigated.
Safe Cryogenic Transfer
Transferring cryogenic liquid is one of the operations most likely to expose employees to splashes, cold vapor, pressure, and oxygen-displacement hazards.
Before transfer:
- Inspect the receiving container.
- Verify that it is designed for the cryogen.
- Confirm adequate capacity.
- Inspect transfer hoses and connections.
- Verify appropriate ventilation.
- Check oxygen monitoring where provided.
- Wear required PPE.
- Keep unnecessary personnel away.
- Understand how to stop the transfer.
- Know what to do if a leak occurs.
Transfers should be performed slowly enough to control splashing, boiling, and thermal shock.
Employees should not leave filling operations unattended unless the system is specifically designed and procedures permit unattended operation.
Do Not Overfill Cryogenic Containers
Cryogenic containers should not be filled beyond their safe capacity.
Adequate vapor space and proper venting are necessary for safe operation.
Overfilling can increase the potential for:
- Liquid discharge.
- Splashing.
- Blocked vents.
- Pressure problems.
- Cryogen entering areas not designed for liquid contact.
Follow manufacturer instructions for filling levels and procedures.
Cryogenic PPE
Appropriate cryogenic PPE should be worn whenever handling or transfer could expose an employee to cryogenic liquid, cold gas, or extremely cold surfaces.
OSHA’s laboratory guidance identifies protective clothing such as eye/face protection, gloves, long-sleeved clothing, laboratory coats, and aprons for applicable cryogenic operations.
The exact PPE should be determined by the hazard assessment.
Eye and Face Protection
Eye protection should be worn when working with cryogenic fluids.
Operations with significant splash potential may require:
Safety goggles + Face shield
A face shield provides additional protection for the face but should not automatically be considered a substitute for appropriate primary eye protection.
OSHA’s laboratory guidance recommends a full face shield when pouring cryogens, working with wide-mouth Dewars, or working around cold boil-off gas exhaust.
Cryogenic Gloves
Cryogenic gloves are designed to protect the hands from incidental contact with cold surfaces, cold vapor, and splashes.
They should generally be:
- Insulated.
- Loose fitting enough to remove quickly.
- Appropriate for cryogenic service.
- Long enough to protect the wrists where needed.
- Dry and in good condition.
Cryogenic gloves should not be considered suitable for immersing the hands in liquid nitrogen or another cryogenic liquid.
They provide protection against incidental exposure—not unlimited protection from direct liquid contact.
Do Not Use Wet Gloves
Water can freeze rapidly when exposed to cryogenic temperatures.
Wet gloves can:
- Freeze.
- Lose flexibility.
- Transfer cold more rapidly.
- Potentially freeze to the skin or equipment.
Cryogenic gloves should be kept dry and replaced when wet or damaged.
Clothing
Appropriate clothing can reduce the severity of a cryogenic splash.
Depending on the operation, this may include:
- Long pants.
- Long sleeves.
- Laboratory coat.
- Cryogenic apron.
- Closed footwear.
- Other protective clothing.
Clothing should be arranged so cryogenic liquid is less likely to become trapped against the body.
Avoid cuffs, open pockets, or other features that could collect liquid where practical.
Footwear
Closed footwear that provides adequate coverage should be worn.
For operations involving larger quantities or significant splash potential, additional foot protection may be appropriate.
Pants should generally be positioned so liquid is less likely to be directed into footwear.
For additional PPE guidance, see Laboratory PPE.
Material Embrittlement
Many materials become brittle at cryogenic temperatures.
Materials not designed for cryogenic service can:
- Crack.
- Shatter.
- Lose flexibility.
- Lose structural strength.
- Fail unexpectedly.
This can affect:
- Plastics.
- Elastomers.
- Seals.
- Tubing.
- Metals.
- Glass.
- Adhesives.
Only equipment and materials suitable for the expected cryogenic temperature should be used.
Do not improvise cryogenic systems using ordinary tubing, containers, fittings, or seals without verifying their suitability.
Thermal Shock
Rapid cooling can create significant thermal stresses.
Glassware and other materials may crack or shatter when exposed too quickly to cryogenic temperatures.
Use containers specifically designed for cryogenic service and follow appropriate cooling and filling procedures.
Damaged or ordinary glass containers should not be substituted for approved cryogenic vessels.
Liquid Oxygen Safety
Liquid oxygen presents hazards beyond extreme cold.
Oxygen itself is not flammable, but an oxygen-enriched environment can cause combustible materials to ignite more readily and burn much more intensely.
Liquid oxygen should be kept away from:
- Oils.
- Greases.
- Organic materials.
- Flammable liquids.
- Combustible materials.
- Ignition sources.
- Equipment not designed for oxygen service.
OSHA’s laboratory guidance also warns that certain cryogenic systems can condense oxygen from the atmosphere, creating an oxygen-enriched material capable of violent reaction when combustible materials are present.
Oxygen Enrichment From Cryogenic Systems
Oxygen enrichment is not limited to containers of liquid oxygen.
Cryogenic surfaces colder than the boiling point of oxygen can condense oxygen from the surrounding air.
Repeated condensation may allow oxygen-enriched liquid to accumulate.
This can create a serious fire or explosion hazard if the oxygen-enriched material contacts:
- Oil.
- Grease.
- Organic compounds.
- Combustible insulation.
- Other fuels.
Cryogenic system design and operating procedures should consider this hazard where applicable.
Liquid Hydrogen and Flammable Cryogens
Liquid hydrogen and certain other cryogenic materials introduce substantial flammability and explosion hazards in addition to cryogenic hazards.
Controls may require:
- Specialized ventilation.
- Ignition-source control.
- Bonding and grounding.
- Gas detection.
- Specialized equipment.
- Hazardous-location electrical equipment.
- Restricted access.
- Detailed emergency procedures.
These materials require chemical-specific procedures and should not be treated simply as “very cold liquids.”
Cryogenic Storage Areas
Cryogenic storage areas should be:
- Adequately ventilated.
- Appropriate for the quantity stored.
- Protected from physical damage.
- Accessible to authorized personnel.
- Kept away from incompatible hazards.
- Arranged to prevent blocked exits.
- Provided with appropriate warning signs.
- Evaluated for oxygen-deficiency hazards.
Large cryogenic inventories may require additional engineering controls, monitoring, alarms, or facility-design considerations.
Storage should also allow pressure-relief devices to discharge safely.
Cryogens in Small Rooms
Small rooms, closets, cold rooms, equipment rooms, and other enclosed areas deserve particular attention.
A cryogen release that presents little oxygen-deficiency risk in a large, well-ventilated space could become life-threatening in a small room.
The assessment should consider the credible quantity that could be released, not merely the amount normally expected to boil off.
If a hose breaks or vessel fails, how low could the oxygen concentration become?
That is a much more useful safety question than:
“We have always stored it here without a problem.”
Cryogens in Elevators
Transporting cryogenic liquids in elevators can create a special risk because the elevator is a small enclosed space.
If a significant release occurs while an employee is inside, oxygen concentration can fall rapidly.
Facilities handling substantial cryogenic quantities should evaluate whether employees should ride in the elevator with the cryogen or whether procedures should require unaccompanied transport with controls preventing other passengers from entering.
The appropriate procedure depends on the quantity, container, building configuration, ventilation, and hazard assessment.
Cryogenic Transport
When moving cryogenic containers:
- Use appropriate carts or transport equipment.
- Secure containers against tipping.
- Protect valves and fittings.
- Avoid unnecessary impacts.
- Keep routes clear.
- Use freight elevators or designated routes where required.
- Follow facility procedures for elevator transport.
- Do not drag or roll containers not designed for that method.
- Ensure the destination is prepared to receive the material.
Large containers should not be manually handled in a manner that could result in loss of control.
Cryogenic Spills and Releases
A cryogenic spill can create several simultaneous hazards:
Extreme cold + Reduced visibility + Oxygen displacement + Pressure + Slippery surfaces
Depending on the cryogen, it may also create:
Fire + Oxygen enrichment + Chemical reactivity
Employees should not automatically attempt to clean up a cryogenic spill.
For a significant release:
- Warn others.
- Move away from the release.
- Evacuate if required.
- Do not enter an oxygen-deficient area.
- Follow emergency procedures.
- Contact appropriate emergency or safety personnel.
Ventilation and atmospheric conditions should be evaluated before employees reenter an affected area when an oxygen-deficiency hazard may exist.
Do Not Attempt an Unprotected Rescue
If a person collapses in an area where nitrogen, helium, argon, carbon dioxide, or another asphyxiant may have displaced oxygen:
Do not rush into the area.
A rescuer breathing the same atmosphere can collapse as well.
OSHA records contain multiple fatal incidents in which oxygen displacement from nitrogen caused deaths, including secondary victims attempting to investigate or help.
Call emergency responders and follow the facility’s rescue procedures.
Cryogenic First Aid
Cold Contact or Frostbite
If cryogenic liquid contacts the skin:
- Remove the person from the source of exposure.
- Remove clothing or jewelry that is not frozen to the skin and could restrict circulation.
- Do not rub the affected area.
- Do not apply direct high heat.
- Obtain appropriate medical attention.
Follow the applicable SDS and established first-aid procedures.
Eye Exposure
Cryogenic liquid or cold gas contacting the eyes requires immediate attention.
Use appropriate emergency eyewash procedures and obtain prompt medical evaluation.
Suspected Oxygen Deficiency
A person exposed to an oxygen-deficient atmosphere requires emergency medical attention.
Do not enter the hazardous atmosphere to retrieve the person unless trained and equipped for the required rescue.
Emergency Planning
Laboratories using cryogenic liquids should establish procedures for foreseeable emergencies such as:
- Cryogenic spills.
- Vessel failure.
- Transfer-hose failure.
- Pressure-relief discharge.
- Oxygen-deficiency alarms.
- Ventilation failure.
- Employee exposure.
- Fire.
- Power failure affecting cryogenic systems.
- Loss of vacuum insulation.
Employees should know:
When to evacuate.
Where to go.
Who to contact.
What alarms mean.
When not to enter an affected area.
Emergency planning is particularly important because some cryogenic emergencies cannot be safely managed by ordinary laboratory personnel.
Working Alone With Cryogenic Liquids
Working alone should be evaluated carefully when cryogenic operations involve:
- Large quantities.
- Transfers.
- Enclosed areas.
- Significant oxygen-deficiency potential.
- High-pressure systems.
- Unfamiliar procedures.
- Highly hazardous cryogens.
The laboratory should determine which operations may be performed alone and which require another person to be present or an established monitoring/check-in system.
Higher-risk cryogenic work should not be treated the same as routine handling of a small Dewar.
Cryogenic Equipment Inspection
Cryogenic equipment should be inspected according to manufacturer recommendations, facility procedures, and the hazards involved.
Inspection may include:
- Dewars.
- Storage vessels.
- Transfer lines.
- Hoses.
- Valves.
- Pressure regulators.
- Pressure-relief devices.
- Vacuum systems.
- Oxygen monitors.
- Alarms.
- Ventilation systems.
- Carts and restraints.
- PPE.
OSHA’s laboratory guidance recommends maintaining cryogenic systems in their approved working condition and maintaining appropriate inspection schedules and records.
Defective equipment should be removed from service or appropriately controlled until repaired.
Cryogenic Safety Training
Employees should receive cryogenic safety training before independently handling cryogenic materials.
Training should address, as applicable:
- Properties of the cryogen.
- Extreme-cold hazards.
- Frostbite and cold burns.
- Oxygen displacement.
- Asphyxiation.
- Oxygen enrichment.
- Pressure buildup.
- Pressure-relief devices.
- Container and Dewar safety.
- Transfer procedures.
- Ventilation.
- Oxygen monitors and alarms.
- Cryogenic PPE.
- Material compatibility.
- Storage.
- Transportation.
- Spill procedures.
- Emergency response.
- First aid.
- Rescue limitations.
OSHA’s Laboratory Safety Guidance specifically identifies cryogenic safety and operational training as an employer responsibility for minimizing cryogenic hazards.
Common Cryogenic Safety Mistakes
Common problems include:
- Assuming liquid nitrogen is harmless because it is not toxic.
- Using cryogens in inadequately ventilated rooms.
- Ignoring oxygen-deficiency potential.
- Ignoring an oxygen-monitor alarm.
- Entering an alarmed area to investigate.
- Attempting an unprotected rescue.
- Using ordinary gloves instead of appropriate cryogenic gloves.
- Assuming cryogenic gloves permit hand immersion.
- Using wet cryogenic gloves.
- Failing to wear eye or face protection.
- Sealing cryogenic liquid in an unvented container.
- Blocking pressure-relief devices.
- Trapping liquid between closed valves.
- Using containers not designed for cryogenic service.
- Overfilling Dewars.
- Leaving filling operations uncontrolled.
- Using damaged transfer hoses.
- Failing to evaluate elevator transport.
- Ignoring excessive frost or unusual boil-off.
- Storing excessive quantities in small rooms.
- Treating liquid oxygen like liquid nitrogen.
- Failing to account for oxygen condensation on extremely cold equipment.
Cryogenic Safety Checklist
A practical Cryogenic Safety Checklist can include:
☐ Employees understand the hazards of the cryogen being used.
☐ SDS information is readily available.
☐ A hazard assessment has been completed for cryogenic operations.
☐ Cryogen quantities are appropriate for the room and ventilation.
☐ Oxygen-deficiency hazards have been evaluated.
☐ Adequate ventilation is provided.
☐ Oxygen monitoring is provided where warranted by the hazard assessment.
☐ Oxygen monitors are maintained and tested.
☐ Employees understand oxygen-monitor alarms.
☐ Employees know not to enter an alarmed oxygen-deficient area.
☐ Cryogenic containers are designed for their intended service.
☐ Dewars are in good condition.
☐ Containers are not improperly sealed.
☐ Pressure-relief devices are installed where required.
☐ Pressure-relief devices are unobstructed.
☐ Trapped-liquid conditions have been addressed.
☐ Transfer hoses and fittings are compatible and in good condition.
☐ Filling and transfer procedures are established.
☐ Containers are not overfilled.
☐ Cryogenic PPE is available.
☐ Appropriate eye protection is used.
☐ Face shields are used for applicable splash hazards.
☐ Appropriate cryogenic gloves are used.
☐ Cryogenic gloves are dry and in good condition.
☐ Employees understand the limitations of cryogenic gloves.
☐ Appropriate clothing and footwear are worn.
☐ Materials and equipment are suitable for cryogenic temperatures.
☐ Storage areas are adequately ventilated.
☐ Containers are protected from tipping and physical damage.
☐ Cryogenic transport procedures are established.
☐ Elevator transportation has been evaluated.
☐ Liquid oxygen receives appropriate oxidizer controls.
☐ Flammable cryogens receive additional fire and explosion controls.
☐ Cryogenic spills and releases are addressed in emergency procedures.
☐ Employees understand when evacuation is required.
☐ Employees understand that unprotected rescue is prohibited.
☐ Cryogenic equipment is periodically inspected.
☐ Employees receive appropriate cryogenic safety training.
☐ Identified deficiencies are corrected and documented.
Building a Cryogenic Safety Program
An effective cryogenic safety program should address the entire process rather than focusing only on PPE.
A useful approach is:
Identify the Cryogen → Evaluate the Quantity and Location → Assess Oxygen-Deficiency and Other Hazards → Provide Ventilation and Engineering Controls → Use Proper Containers and Pressure Relief → Establish Safe Transfer Procedures → Select Appropriate PPE → Prepare for Spills and Emergencies → Train Employees → Inspect and Maintain Equipment
The most serious cryogenic hazard may not be the one employees can see.
A visible splash makes the extreme-cold hazard obvious. An invisible reduction in atmospheric oxygen may provide little or no warning.
That is why ventilation, hazard assessment, monitoring where warranted, and emergency procedures are just as important as cryogenic gloves and face protection.
Need a Cryogenic Safety Checklist?
Use a Cryogenic Safety Checklist to evaluate liquid nitrogen and other cryogenic operations, oxygen-deficiency hazards, ventilation, oxygen monitoring, Dewars and containers, pressure-relief systems, transfer procedures, cryogenic PPE, storage, transportation, spills, emergency procedures, and employee training.