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Vapor Density: Vapor Density Ratio Molecular Weight of The Material Composite Molecular Weight of Air (29) MW 29

Vapor density determines how well vapor will disperse in air after emission, with heavy vapor less likely to disperse and more likely to collect in low areas posing a fire hazard. Vapor density is expressed as the ratio of a gas's vapor density to air's vapor density of 1, calculated using molecular weights, with ratios over 1 indicating vapor heavier than air.

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91 views1 page

Vapor Density: Vapor Density Ratio Molecular Weight of The Material Composite Molecular Weight of Air (29) MW 29

Vapor density determines how well vapor will disperse in air after emission, with heavy vapor less likely to disperse and more likely to collect in low areas posing a fire hazard. Vapor density is expressed as the ratio of a gas's vapor density to air's vapor density of 1, calculated using molecular weights, with ratios over 1 indicating vapor heavier than air.

Uploaded by

Jagdeep Sekhon
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Vapor density

Vapor density will determine how well the vapor will be dispersed in the air after its
emission. Heavy vapor will not be effectively dispersed in the air and may collect in
low areas and represent a fire hazard.

Vapor density is often expressed in terms of the ratio of the gas vapor density to the
vapor density of air. With air taken as unity (value=1), the vapor density ratio of the gas
indicates the relative density of the vapor in the air:

Molecular Weight of the material


Vapor density ratio =
Composite molecular weight of air (29)

Examples:

 Exxsol™ Heptane has a composite MW of 98. Its vapor density ratio is then of 3.4.
This simple calculation indicates that Exxsol™ Heptane gaseous emissions may not
homogeneously mix with surrounding air and as it is heavier than air can create high gas
concentration pockets at low areas which may present a higher flammability risk.
 Exxsol™ D40 has a vapor density of 5.0 (air=1)
 Isopar™ H (AM) has a vapor density of 5.3 (air=1)

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