Petroleum industry workers have a potential for exposure to a variety of organic compounds while performing a variety of tasks. Therefore, it could be useful to have an exposure screening monitor with a low enough detection limit for these compounds. A direct-reading data-logging ionizable hydrocarbon monitor with low concentration capability could help identify potential toxic exposures more economically than laboratory-based monitoring methods. This paper evaluated the IonScience CUB monitor for usefulness in monitoring routine full-shift hydrocarbon exposure by measuring the CUB’s accuracy and bias, response time, and other specifications relevant for use in screening petroleum worker exposures. The CUB was chosen because it is one of the first pocket-sized wearable data-logging monitors with the ability to detect (parts per billion) organic compounds in low concentrations (parts per billion). The IonScience CUB was repeatedly exposed to test concentrations of isobutylene and n-hexane delivered from purchased calibration cylinders. Four concentrations were tested: 0.1, 1, 10 and 100 ppm. In addition, workers in a petroleum refinery wore the CUB side-by-side with traditional charcoal tube and pump monitoring methods for laboratory analysis of total hydrocarbons. For the measurements against the known calibration gases, the CUB’s peak and time-weighted measurements agreed well with the expected values. For the refinery personnel monitoring, there were some differences between the CUB and the laboratory charcoal tube results that could be due to the CUB sensor response to the real-world mixtures, the CUB baseline/zero measurements, and other factors such as temperature changes in the workplace. This study indicates the usefulness of the CUB in screening workers’ exposure to ionizable hydrocarbons. The CUB is small enough for workers to wear repeatedly day after day to screen for potential toxic exposures. Furthermore, the CUB’s data logging features can be used to capture peak exposure events and estimate time-weighted average exposures. Occupational exposure limits to petroleum compounds are continuously being lowered. With the ability to detect low concentrations, i.e., parts per billion, the CUB can be useful to screen exposures within the present and future lower exposure limits.