Potassium hydroxide (KOH), commonly known as caustic potash, is a strong inorganic base that appears as a white solid, flakes, or pellets. It is widely used in manufacturing soft soaps, as an electrolyte in alkaline batteries, and in various industrial chemical processes. While concerns exist about the fire or explosion risk of industrial chemicals, potassium hydroxide itself is not flammable or explosive. Its true dangers lie in its extreme chemical reactivity and corrosivity.
The Direct Answer: Flammability Profile
Potassium hydroxide is classified as a non-combustible material; it will not ignite and burn in air. As a strong alkali, it lacks the carbon-hydrogen structures typical of organic compounds that sustain combustion.
If a fire occurs in a surrounding area, standard extinguishing media like water spray, dry chemical, or carbon dioxide can be used. The primary concern is not the KOH itself but the potential for heat to cause decomposition, producing poisonous gases like potassium oxides. If water contacts KOH during a fire, the resulting exothermic reaction can generate enough heat to ignite nearby combustible materials.
Primary Hazard: Corrosivity and Chemical Burns
The greatest immediate hazard posed by potassium hydroxide is its extreme corrosivity, which causes severe chemical burns upon contact with tissue. Due to its strong alkaline nature, the mechanism of injury is highly destructive. When KOH contacts skin, it rapidly initiates saponification—the breakdown and dissolving of fats and oils.
Tissue damage is compounded by the hygroscopic nature of KOH, which rapidly extracts water from cells, increasing burn severity. Unlike acid burns, which coagulate protein and limit penetration, alkali burns continue to dissolve tissue and penetrate deeply, leading to scarring. Direct eye contact, whether with solid flakes or a solution, is a major hazard that can cause rapid, severe destruction of eye tissue and result in permanent blindness. Ingestion presents a life-threatening risk, causing severe corrosive injury and potential perforation of the esophagus and stomach.
Reactivity and Exothermic Danger
While potassium hydroxide is not flammable, its reactivity with other common substances creates significant secondary hazards involving heat and flammable gas generation. The most notable danger comes from its highly exothermic reaction with water, meaning it releases a great amount of heat. The dissolution of KOH pellets or flakes in water is so vigorous that the solution can rapidly boil, creating a risk of thermal burns and dangerous splatter of the corrosive solution.
A similar, violent, and highly exothermic reaction occurs when KOH is mixed with strong acids. This neutralization reaction can cause containers to rupture or spray corrosive material due to the rapid temperature increase. Another serious secondary hazard involves its reaction with specific metals, such as aluminum, zinc, tin, and lead. This corrosive reaction generates flammable and explosive hydrogen gas, which can accumulate in confined spaces and pose a fire or explosion risk.
Safe Handling and Emergency Procedures
Working with potassium hydroxide requires strict adherence to safety protocols to mitigate corrosive and reactive hazards. Personal protective equipment (PPE) is mandatory and includes chemical-resistant gloves (such as neoprene or butyl rubber), tightly fitting safety goggles, and a face shield. A lab coat or full protective clothing must be worn to prevent skin contact.
Proper storage is necessary to control its reactivity and hygroscopic nature. KOH must be kept in a tightly closed, non-metal container and stored in a cool, dry, well-ventilated area. It must be kept strictly separated from incompatible materials, including strong acids, water, and reactive metals.
In the event of skin or eye contact, immediate first aid involves flushing the affected area with large amounts of water for at least 15 to 30 minutes. Contaminated clothing must be removed quickly, and medical attention should be sought immediately, even if the injury appears minor. For spills, the area should be evacuated, and the solid material collected carefully into sealed containers, avoiding the use of water for cleanup. The material must then be disposed of as a hazardous waste.