Analyze an SDS

Glossary / Physical properties

Vapor pressure

Vapor pressure is the pressure exerted by the vapor above a liquid or solid at a given temperature, and it indicates how readily the material evaporates. A higher vapor pressure means the substance gives off more vapor and is more likely to be breathed or to form a flammable atmosphere.

Explanation

Vapor pressure rises sharply as temperature goes up, so a figure only means something when the temperature is stated. The SDS will usually quote the value together with a reference temperature. Two products can compare very differently at room temperature and at a hot process temperature.

In practice, vapor pressure tells you how volatile a material is. A solvent such as acetone evaporates fast and fills the air with vapor, while a heavy oil gives off very little. High volatility raises the inhalation exposure, and for flammable liquids it means the air above the liquid reaches an ignitable mixture sooner. It is closely tied to Flash point, Boiling point and Evaporation rate.

Vapor pressure also affects containers. Volatile liquids in a closed drum or tank in the sun build pressure, so containers may need venting or protection from heat. Open containers of volatile materials add to workplace exposure and should be kept closed.

Solids can have measurable vapor pressure too. Some give off enough vapor to matter, so a low reading does not always mean no inhalation concern. Pair it with the exposure limits on the SDS to judge real risk.

What to do and watch for

  • Keep containers of volatile materials closed and away from heat.
  • Expect higher airborne levels from high-vapor-pressure products, especially when heated.
  • Use ventilation suited to the volatility of what you are handling.

Where it appears on an SDS

SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.

Related terms

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