UN 1824 — Sodium hydroxide, solution

Sodium hydroxide solution, also known as caustic soda solution or lye solution, is a highly alkaline substance with a wide range of industrial applications, including the manufacture of paper, textiles, and soap. It is classified as a DOT class 8 material, indicating that it is toxic and corrosive. First responders may encounter sodium hydroxide solution during transportation accidents or at industrial sites where it is used or stored. The scale of production and transport of sodium hydroxide solution is significant, with millions of tons being produced and transported each year. As a result, it is essential for first responders to be aware of the hazards associated with this substance and to know how to respond safely and effectively. Sodium hydroxide solution is a clear to slightly cloudy colorless liquid with no distinct odor, and is highly alkaline and viscous.

Hazard overview: Sodium hydroxide solution is highly toxic and corrosive, and can cause severe injury or death if inhaled, ingested, or if it comes into contact with the skin or eyes. The substance can also produce irritating, corrosive, and toxic gases when it comes into contact with fire or water. The LC50 value for sodium hydroxide solution is not available, but it is known to be highly toxic and can cause severe burns and respiratory problems. The substance is also highly reactive, and can dissolve exothermically in water, generating significant heat that may cause boiling or spattering. In the worst-case scenario, sodium hydroxide solution can cause a large-scale release of toxic and corrosive gases, posing a significant threat to people and the environment. The vapor density of sodium hydroxide solution is not applicable, as it is a non-volatile aqueous solution.

Response guidance: In the event of a spill or leak of sodium hydroxide solution, it is essential to isolate the area immediately, using the isolation distances from the ERG guide. For small spills, isolate the area 25m in all directions, and for large spills, isolate the area 50m and evacuate downwind areas. The correct suppression agent for sodium hydroxide solution is water spray for cooling only, and CO2 and dry chemical are ineffective on caustic liquids. Decontamination is also crucial, and should be carried out using a suitable cleaning solution and protective equipment. CHEMTREC should be contacted immediately in the event of a spill or leak, and evacuation zones should be established to protect people and the environment.

Firefighter training notes: First responders should receive training on the safe handling and response to sodium hydroxide solution, including the use of PPE and decontamination procedures. A common tactical error when responding to a spill or leak of sodium hydroxide solution is to use CO2 or dry chemical suppression agents, which are ineffective on caustic liquids. ICS position needs and mutual aid criteria should also be established to ensure a coordinated response to a spill or leak of sodium hydroxide solution.

Regulatory context: Sodium hydroxide solution is classified as a DOT class 8 material, indicating that it is toxic and corrosive. The OSHA PEL for sodium hydroxide solution is not established, but the substance is highly toxic and corrosive, and should be handled with caution. Sodium hydroxide solution is also listed on the CERCLA list, indicating that it is a hazardous substance that requires special handling and response procedures.

Storage & handling: Sodium hydroxide solution should be stored in a cool, well-ventilated area, away from incompatible materials such as acids and metals. The temperature limit for storage is not established, but the substance should be kept away from heat sources and ignition sources. The top 3 incompatible materials for sodium hydroxide solution are acids, metals, and organic materials, and the substance should be stored in a separate area to prevent contamination and reaction.