Vinegar (a dilute solution of acetic acid) and hydrogen peroxide are common household substances often used separately as cleaning agents. Both compounds are known for their individual abilities to disinfect and clean various surfaces. When combined, however, they do not simply create a stronger cleaning solution. Instead, the mixture triggers a chemical process that transforms these relatively mild household chemicals into a new, significantly more potent, and potentially hazardous compound. This transformation is why mixing them is strongly discouraged outside of controlled, commercial environments.
The Chemical Transformation
The chemical interaction between vinegar and hydrogen peroxide is an equilibrium process that generates a new chemical species. Household vinegar contains acetic acid, and hydrogen peroxide is H2O2. When combined, these two molecules react to form peracetic acid and water.
This reaction is reversible, meaning the new compound, peracetic acid, is always present alongside the original reactants in a state of balance. The concentration of the final product depends directly on the concentrations of the starting materials used.
Because household concentrations of both vinegar (typically 5% acetic acid) and hydrogen peroxide (often 3%) are low, the rate at which peracetic acid forms at room temperature is slow. However, the reaction is spontaneous and continues over time. The resulting mixture is unstable, and its composition constantly shifts, making it impossible to predict the potency of the solution created in a home setting.
Properties of the Resulting Compound
The product of this reaction, peracetic acid (PAA), is a powerful oxidizing agent that fundamentally changes the mixture’s properties. PAA works by destroying the cell walls of microorganisms, making it highly effective against a wide variety of pathogens. It is classified as a broad-spectrum antimicrobial, demonstrating efficacy against bacteria, fungi, viruses, and bacterial spores.
This compound is widely utilized in industrial and commercial applications requiring high-level disinfection. For example, PAA is a common agent for sanitizing equipment in food and beverage processing plants and for sterilizing medical devices. Its strong germicidal action is valued because microorganisms cannot easily develop tolerance to it.
In controlled settings, a benefit of peracetic acid is its decomposition profile. After use, PAA naturally breaks down into harmless byproducts: acetic acid, oxygen, and water. This process leaves behind no toxic residue on treated surfaces, which is why it is preferred for applications involving food contact.
Safety Concerns and Handling
Despite its industrial utility, creating peracetic acid by mixing vinegar and hydrogen peroxide at home is hazardous. The primary risk stems from the highly corrosive nature of the resulting peracetic acid. Even at the unpredictable concentrations formed by household ingredients, the solution can be caustic and cause severe chemical burns upon contact with skin and eyes.
The reaction also produces vapors that are highly irritating to the respiratory system, throat, and nasal passages. Inhaling these fumes, especially in an enclosed space, can lead to serious respiratory distress and inflammation. The strong, pungent, vinegary odor indicates the presence of this hazardous compound.
Instability and Storage Risks
The unstable nature of the homemade solution compounds the risk. The continuous chemical reaction is exothermic, meaning it produces heat, which contributes to the mixture’s overall volatility. Furthermore, the decomposition of peracetic acid over time can lead to the buildup of gas pressure if the solution is stored in a sealed container.
In highly concentrated forms (above 42%), peracetic acid can become an explosion hazard, though this level is unlikely with typical household products. The lack of control over the precise concentration and stability makes any homemade mixture a significant and unpredictable hazard. The safest practice is to use vinegar and hydrogen peroxide separately, wiping down the surface between applications.