Equations $3-12$ and $3-14$ can be applied to nonenclosed exposures by using an effective ventilation rate. The effective ventilation rate for outside exposures has been estimated at $3000$ ft$^3/$min$.$

A worker is standing near an open passageway of a tank containing $2-$butoxy$$ethanol $($molecular weight $=118).$ The passageway area is $7$ ft$^2.$ Estimate the concentration $($in ppm$)$ of the vapor near the passageway opening. The vapor pressure of the $2-$butoxy$$ethanol is $0\mathrm{.}6$ mm Hg$.$