Overview of Hazards

Sodium azide is highly toxic. Ingestion of 100 to 200 mg can result in headache, respiratory distress, and diarrhea. Target organs are the central nervous system and the brain. Sodium azide in solution is rapidly absorbed through the skin. 

Sodium azide rapidly hydrolyzes in water and acids, forming hydrazoic acid (HN₃), a highly toxic and volatile liquid solution that poses a serious inhalation hazard.

Sodium azide decomposes violently when heated to 275⁰C. It reacts violently with carbon disulfide, bromine, nitric acid, and dimethyl sulfate. It reacts with halogenated organics (e.g., dichloromethane), forming explosive organic azides.

When sodium azide or its solutions come into contact with metal surfaces such as lead, copper, zinc, silver, or brass, heavy metal azides, which are highly shock-sensitive explosives, are formed. Even dilute solutions can accumulate enough azide salts over time to cause a serious explosion. Mixing sodium azide solutions with heavy metal salts including mercuric chloride can lead to explosions.

Due to the hazards associated with solid sodium azide, buying dilute solutions of 5% or less sodium azide is recommended.

Safe Handling

Wear standard laboratory attire i.e., closed-toe shoes, long pants, a lab coat, eye protection, and nitrile gloves when handling sodium azide powder or solution. It is recommended to double glove or wear thicker nitrile rubber gloves. Remove gloves immediately if contaminated, and wash hands with soap and water. Always wash your hands after your work is done.

• Handle sodium azide powder or solutions >5% only in a properly functioning fume hood.
• When weighing dry powder and the scale cannot be located inside the enclosure, use the following procedure:
  

1. Tare the container with lid.
2. Add the chemical inside the fume hood using a plastic or ceramic spatula. Do NOT use a metal spatula. 
3. Close the container. 
4. Weigh the container.
5. Add the solvent inside the hood.
   

• If solutions are manipulated in a way that generates aerosols (e.g., sonicating or pressurizing), do this inside the hood if the container has to be open, or keep the container closed. 
• Clean the work area by wiping with soap and water once your work is done. 
• Clearly label all equipment and instruments that come into contact with sodium azide, and thoroughly flush them with water to avoid the build-up of azide salts. Be careful servicing metal parts that have come into contact with sodium azide.

Emergency Procedures

Accidental Exposure

Skin Contact

Remove contaminated clothing and rinse off affected skin immediately with soap and copious amounts of water for at least 15 min.

Eye Contact

Use the eye wash to rinse the eye thoroughly for at least 15 min, occasionally lifting upper and lower eyelids and rolling the eyeballs around. 

Inhalation

Move into fresh air immediately.

Ingestion

Rinse mouth with water. Seek medical attention immediately.Provide the medical team with the Safety Data Sheet.

Spills

Sweep up spills of solid sodium azide carefully, and try to avoid dust formation. Use a cloth dampened with soap water with a pH of 10 if necessary to avoid dust. Place the material into a non-metal container. 

Wipe up solutions with chemical absorbent pads. 

Once cleaned up, wipe the area thoroughly with water with a pH of 9. 

If the spill is outside the hood and too big to handle safely, call 911. Evacuate the area immediately, alerting others. Close the door and prevent people from entering.

Storage

Store sodium azide in a cool, dry area away from heat and open flames. Separate it from incompatible material such as halogenated hydrocarbons, metals, water, acids, and acid chlorides. Avoid contact with metal shelves or containers. Use secondary containment if necessary.

Waste Disposal

Under no circumstances should you pour sodium azide solutions down the drain. Reaction with lead or copper pipes can build up highly explosive azide salts. Dispose of all used or unwanted material, including dilute solutions, through DRS.

Destruction

Solutions of 5% or less of sodium azide can be destroyed by reaction with freshly prepared nitrous acid. Destruction MUST be conducted in a working fume hood and in an open container due to the release of toxic nitric oxide (NO) gas.

2NaNO₂ + H₂SO₄ → 2HNO₂ + Na₂SO₄

2NaN₃ + 2HNO₂ → 3N₂(g) + 2NO(g) + 2NaOH

The procedure is from “Prudent Practices for Laboratories.” An aqueous solution with no more than 5% NaN₃ is placed in a three-necked flask equipped with a stir bar, addition funnel, and outlet that vents into the fume hood. A 20% aqueous solution of sodium nitrite containing 1.5 g (ca. 40% excess) of sodium nitrite per gram of sodium azide is added with stirring.

A 20% aqueous solution of sulfuric acid is then gradually added via the addition funnel until the reaction mixture is acidic. The order of addition is very important! When the evolution of gas ceases, the solution should be tested with starch-iodide paper. A blue color indicates excess nitrite is present and decomposition is complete. 
If the mixture is neutral in pH (6-10) and does NOT contain heavy metals or other toxic compounds, it can be poured down the drain (see drain disposal requirements LINK).

References

Center for Disease Control and Prevention: Facts about sodium azide
https://emergency.cdc.gov/agent/sodiumazide/basics/facts.asp

P.G. Urben (Ed.), Bretherick’s Handbook of Reactive Chemical Hazards 6th Ed., Oxford, Butterworth-Heinemann, 1999.

National Research Council: Prudent Practices for Laboratories (Supplemental CD). National Academy Press: Washington, DC, 2011.