Published exposure data from systematic sampling of haz- ardous agents on upstream operations are limited or pub- lished some years ago. Since benzene is a natura component of crude oil and natural gas, a few studies have reported data on benzene exposure. Substances, such as hy- drogen sulphide (H2S), are usually well controlled through sealed systems, permit to work systems, gas purging, area and personal monitoring, training, emergency plans, etc.