Baby oil is commonly found in many homes, leading to questions about its potential fire hazard. Baby oil is not classified as “flammable” but is considered “combustible.” This distinction means the oil will not easily ignite at room temperature. However, it will burn vigorously once it reaches a sufficiently high temperature and is exposed to a flame.
Understanding the Composition of Baby Oil
Baby oil is primarily composed of highly refined mineral oil, a liquid byproduct of petroleum distillation. The final product typically contains approximately 98% mineral oil, with the remaining percentage consisting of added fragrances to provide a pleasant scent.
The molecular structure of mineral oil is a long chain of carbon atoms, making it a relatively heavy and non-volatile hydrocarbon. Because the molecules are large, they do not easily vaporize into the air at normal temperatures. This low volatility is the fundamental reason the oil resists ignition under typical household conditions, unlike lighter oils such as gasoline or alcohol.
Defining Combustible: Conditions for Ignition
The classification of liquids as “flammable” or “combustible” is based on their flash point, which is the lowest temperature at which a liquid produces enough vapor to ignite briefly in the presence of an ignition source. A flammable liquid has a flash point below 100°F (38°C), while a combustible liquid has a flash point at or above 100°F. Since the flash point of most baby oils is high, often around 331°F to 335°F (166°C to 168°C), it falls firmly into the combustible category.
The liquid itself does not burn; instead, it is the invisible vapor mixing with oxygen that ignites. Because baby oil’s flash point is so high, it must be significantly heated before it releases enough vapor to form this ignitable mixture. The autoignition temperature, the point at which the oil spontaneously ignites without any external spark or flame, is also extremely high, typically ranging from 500°F to nearly 700°F (260°C to 370°C).
The primary fire hazard occurs when a porous material, such as a cloth or cotton, absorbs the oil. This is known as the “wicking effect,” where the material acts like a candle wick, drawing the oil up and holding it in place. When a wick-like material is exposed to a flame, it allows the heat to efficiently transfer, vaporizing the oil and sustaining a continuous flame.
Practical Safety Guidelines for Use and Storage
Understanding the combustible nature of baby oil leads to simple safety guidelines for its use and storage. Because the oil requires significant external heat to ignite, it should be kept away from all open flames and high-temperature appliances. Never use baby oil near lit candles, gas stoves, portable heaters, or oil lamps, as these sources can easily provide the necessary heat to reach the flash point.
The most important safety consideration involves materials that have absorbed the oil. Any rags, towels, or clothing soaked with baby oil should never be left in a pile, as porous materials act as wicks and significantly increase the risk of ignition if they contact a heat source.
To safely dispose of oil-soaked items, lay them flat to dry outside in a well-ventilated area, away from direct sunlight or heat. Once fully dried, they can be disposed of in a metal container with a tight-fitting lid. Store the oil itself in its original, tightly sealed container in a cool, dark place away from any heat source.