A tank containing Hydrogen Sulfide $($H$2$S$)$ gas $($molecular weight $34)$ has been over pressured and the flow through the relief device has been opened. A cloud of material has formed downwind of the release.

In this case, the flow of gas has been calculated to be $1\mathrm{.}76$ kg$/$s$.$

For this release, the hydrogen sulfide in the tank is at a pressure of $1$MPa absolute and $25$degree C $,$ the release occurs at ground level, and it is a clear night with a wind speed of $5\mathrm{.}5$ m$/$s$.$

a$.$ Determine the distance downwind that must be evacuated $($in km$).$ Assume that evacuation must occur in any location that exceeds the OSHA PEL.