The Crude Oil Tanker model is a combination type portable HC, O2, and H2s gas detector with an Infrared (NDIR) type sensor, galvanic cell type sensor and Electro-chemical cell type sensor. These sensors provide accurate detection of HC, O2 and H2S levels even in N2 and other inert environments. The measuring ranges of model RX-516 are 0-100%LEL / 0-10%vol for HC, 0-25% vol for O2 and 0-100.0ppm for H2S respectively. A higher range for H2S (0-1,000ppm) is available in model RX-517. A manual switch is used to change the flow to a unique path for high H2S applications to protect the other sensors. The RX-516 / RX-517 has an explosion proof and Intrinsically Safe design so that it can be used safely in any envrionment.