In general, where there are potentially off-site and/or on-site sources that may explain the presence of benzene, factors such as the respective products used at a site, release history and/or environmental conditions – such as geology and hydrogeology, which govern how those products behave in the subsurface – may assist in identifying a source. Where different releases on-site may explain the presence of benzene, factors such as when the release occurred, among other factors, may assist.