Aerosol cans can explode under certain conditions because they are pressurized containers designed to dispense a product using a propellant. The danger arises when the can’s structural integrity is compromised or the internal pressure increases past its design limit. An aerosol can is fundamentally a small pressure vessel, typically made of metal, that holds a liquid product and a gas under significant force. Understanding the physics behind how these common household items function is the first step toward preventing a dangerous rupture.
How Aerosols Maintain Pressure
Aerosol cans rely on a propellant to generate the force necessary to push the product out in a fine mist or spray. This propellant is a gas, such as propane, butane, or nitrogen, that is sealed inside the container along with the product concentrate. The propellant’s role is to maintain an internal pressure that is significantly higher than the surrounding atmospheric pressure, often two to eight times greater.
In many modern cans, the propellant is a liquefied gas that exists as both a liquid and a gas inside the container. As the product is used, the liquid propellant immediately vaporizes to fill the void, which helps maintain a stable pressure until the can is nearly empty. This constant pressure ensures a consistent spray quality. Conversely, propellants like compressed nitrogen remain solely in a gaseous state, and their pressure naturally drops as the product is discharged.
Triggers for Catastrophic Failure
An explosion occurs when the internal pressure exceeds the can’s physical design limits, causing a violent rupture of the container wall or valve system. The most common trigger is exposure to extreme heat, such as leaving a can in a hot car or near a stove. As the temperature increases, the propellant gas inside expands rapidly, and its vapor pressure rises dramatically.
Most aerosol cans are designed to withstand pressure, but when the temperature exceeds approximately 120 degrees Fahrenheit, the pressure buildup can compromise the can’s structure. In extreme cases, like a can exposed to direct fire, the rapid heating can cause a Boiling Liquid/Expanding Vapor Explosion (BLEVE), where the container fragments are ejected as projectiles. Physical damage is a second major trigger, as dents or punctures compromise the metal’s structural integrity, making it more vulnerable to rupture even at normal operating pressures. Piercing the can causes a sudden, forceful release of pressure that can turn the container into an unguided missile.
Essential Safety and Storage Guidelines
Preventing an aerosol can explosion requires following guidelines focused on temperature and physical integrity. Cans should be stored in a cool, dry, and well-ventilated location, away from direct sunlight, open flames, or any source of heat. Never store a can near heat-generating appliances like ovens, radiators, or space heaters.
It is important to keep the can’s body free from damage; avoid dropping, crushing, or denting the container, as this weakens the metal structure. When disposing of an empty can, never attempt to puncture it or throw it into a fire, even if the product is fully dispensed. Even an “empty” can may retain residual propellant gas under pressure, which can still cause an explosion upon incineration. Local regulations should be checked for the correct disposal of partially full or empty cans, as some may be classified as hazardous waste.