Last Revised: July 19, 2022

Revised 7/2022

The requirements in Penn's Chemical Hygiene Plan  SOP: Acutely Toxic Chemicals, SOP:  Irritants, and SOP: Corrosives apply to all work involving osmium tetroxide (CAS 20816-12-0).  The Fact Sheet below gives hazard information and precautions for working with this chemical; however, this information is provided as a supplement to the SOPs, which must first be read and understood by anyone planning to work with this chemical.


Osmium tetroxide is most commonly used in oxidation reactions and for biological staining.


Osmium tetroxide is acutely toxic.  It is a severe irritant (eyes, respiratory tract) and can cause irreversible eye damage.  Direct contact to the eyes may cause blindness.  Osmium tetroxide causes long-term toxicity to liver and kidneys.

Symptoms of Exposure

Osmium tetroxide has poor warning properties of over-exposure and symptoms may be delayed. Seek medical attention if you experience any of the following symptoms during or after work with osmium tetroxide.

  • Watery eyes
  • Gritty feeling in eye
  • Headache
  • Dizziness
  • Skin Irritation/Burns
  • Coughing

Safe Handing

Purchase osmium tetroxide in the lowest quantity and lowest concentration possible.  Purchase the liquid form of this chemical whenever possible.

Prepared stock solutions containing osmium tetroxide must be labeled with the full name of the reagent, the concentration of the solution, any other components of the solution, and a warning label that states the following:


Oxidizing Agent

Severe Irritant

Causes Eye Damage

Toxic to Liver and Kidney  

Open containers of osmium tetroxide or of solutions containing osmium tetroxide must only be handled inside of a chemical fume hood.  Measure quantities of osmium tetroxide volumetrically (i.e. using a micropipette with disposable tips).  If gravimetric analysis is required, place a balance inside of the fume hood or dispense the material into a tared and sealed vessel.

Due to the risk of splashes and equipment failures, do not use a syringe and needle to perform transfers of osmium tetroxide in volumes of greater than 5 mL.  When performing small-volume liquid transfers of chemicals with health hazards, it is not appropriate to use a luer-slip syringe type, because the needle can easily detach from the syringe barrel resulting in chemical splash and exposure.  Luer-lock or integrated-needle syringes must be used with these chemicals if a chemical exposure due to splash presents a significant health risk.

Personal Protective Equipment

Minimum PPE           

  • Long Pants     
  • Closed Shoes                                                         
  • Cotton Lab Coat                                                    
  • Safety Glasses                                                       
  • Nitrile Gloves

Gloves must be changed regularly and disposed of immediately when contaminated.  Additional PPE may be required if you work with large quantities of osmium tetroxide (more than a few mL).  Contact EHRS (x84453) for guidance.

Decontamination and Disposal

Small-spill clean-up and decontamination

Corn oil, sodium sulfide, or sodium sulfite will deactivate osmium tetroxide on labware and on surfaces.

Only attempt to clean-up small spills or contaminated labware inside of a chemical fume hood and only if you are trained to do so safely!

Using corn oil to deactivate

The following instructions were adapted from:

A 2% osmium tetroxide solution will be fully deactivated by two-times the volume of corn oil. 

Add oil to the surface or vessel you wish to decontaminate and wait for the oil to turn black. 

Carefully clean-up the oil with a detergent solution and dispose of any spill clean-up materials as chemically-contaminated waste. 

Solutions of sodium sulfide or sodium sulfite will also reduce aqueous solutions of osmium tetroxide to a less hazardous form.  The used solutions must be disposed of as chemical waste.


Solutions containing osmium tetroxide must be collected as chemical waste in accordance with Laboratory Chemical Waste Management Guidelines.

Disposable labware and other solid materials (such as paper towels, kimwipes, pipet tips, syringes, etc.) that are contaminated with osmium tetroxide must be collected in a sealed, liquidtight, and puncture-proof container that is labeled with a yellow hazardous waste tag. 


Osmium tetroxide is a P-listed waste.  This means that any unused quantities of reagent and empty reagent bottles/containers must be disposed of as hazardous waste.  Do not rinse osmium tetroxide containers or throw them away as regular lab trash.  Label empty osmium tetroxide containers with a yellow hazardous waste tag and request a Chemical Waste Pick-Up Form.


Emergency Contacts

General emergency response information can be found at Emergency Info


General procedures for chemicals spill response can be found in Section X: Chemical Spills in this CHP.

Do not hesitate to call EHRS for assistance with spill cleanup for Acutely Toxic Materials

24 hours: 215-898-4453

Contact Penn Police (511) only if the spill involves a fire, imminent risk of fire, an injury requiring an ambulance, or if there is a hazard that may affect others in the building.