aerosol

The aerosol can produces a fine spray of liquid particles, called an aerosol. When the top button is pressed, a valve is opened, allowing the pressurized propellant in the can to force out a spray of the liquid contents. As the liquid sprays from the can, the small amount of propellant dissolved in the liquid vaporizes, producing a fine spray of small droplets.

Particles of liquid or solid suspended in a gas. Fog is a common natural example. Aerosol cans contain material packed under pressure with a device for releasing it as a fine spray. Most aerosols used chlorofluorocarbons (CFCs) as propellants until these were found to cause destruction of the ozone layer in the stratosphere.

The international community agreed to phase out the use of CFCs. However, the early so-called ‘ozone-friendly’ replacement aerosols were found to also use ozone-depleting chemicals, although they are not as destructive as CFCs. Some of the products sprayed, such as pesticides, can be directly toxic to humans.

Modern aerosol propellants are based on hydrocarbons, carbon dioxide, and nitrogen. In 2002 these propellants accounted for nearly 95% of all aerosol units in the USA. The remaining 5% use HFC propellants, chosen for specialized performance properties, which although a greenhouse gas, account for only 0.3% of US annual greenhouse gas emissions and have much less of an environmental impact than CFCs.