Vapor Pressure

What Is Vapor Pressure?

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. It indicates a chemical substance's volatility and tendency to evaporate into the atmosphere. Not to be confused with atmospheric pressure, vapor pressure is critical in assessing the behavior of hazardous materials during spill or release incidents. Understanding vapor pressure helps responders establish appropriate isolation zones and select suitable personal protective equipment (PPE) during hazardous materials (hazmat) and chemical, biological, radiological, and nuclear (CBRN) operations.

Why Vapor Pressure Matters on the Fireground

Knowing the vapor pressure of a hazardous material informs responders about its potential to form toxic or flammable vapors, influencing containment and evacuation strategies. High vapor pressure substances may require rapid establishment of Hot, Warm, and Cold Zones to protect responders and the public. Accurate vapor pressure data supports decision-making under the Incident Command System (ICS) for effective hazard mitigation.