# Aerosol Formation #fundamental #gas-dispersion #chemistry Aerosols are liquid droplets suspended in air, formed from vapors or gases under specific thermodynamic conditions or by flash evaporation of pressurized liquids. ## Characteristics - Not a gas, but liquid droplets in air - Formed from vapors/gases under thermodynamic conditions - Created by flash evaporation of pressurized liquids - May scatter light, making clouds visible - Dispersion behavior varies between dense and neutrally buoyant ## Formation Mechanisms 1. **Thermodynamic Conditions**: Vapors condense into droplets 2. **Flash Evaporation**: Pressurized liquids rapidly expand 3. **Hygroscopic Properties**: Substances absorb moisture from air ## Examples - Hydrochloric acid (HCl) - Hydrofluoric acid (HF) - Sulfur trioxide (SO3) - forms sulfuric acid droplets ## Detection Considerations - Aerosol droplets absorb temperature and evaporate to form gas/vapor clouds - Dispersion may vary between dense gas and neutrally buoyant behavior - For acid gases, position detectors low to the ground - Aerosol clouds may be visible to the naked eye ## Special Case: SO3 Sulfur trioxide has strong hygroscopic properties: - Immediately absorbs moisture from air upon release - Forms sulfuric acid droplets - Droplets fall to ground, creating pools of acidic liquid - Requires low-level detector placement ## Related Concepts - [[Dense Gas Dispersion]] - [[Neutrally Buoyant Gas]]