As a petroleum inspector, your main duties are to analyze and measure a shipment of petroleum before delivering it to clients. When shipping vessels arrive at a port, you begin by verifying the correct quantity of petroleum and then continue by sampling the cargo from the tanks, which you send to a laboratory to be analyzed. If the analysis confirms that the cargo is to specifications, you can release it for distribution. If it is not to specification, you must make additional tests, reporting your findings to your client or supervisor.