Background: Excessive ventilation of sick and injured patients is associated with increased morbidity and mortality. Combat Medical Systems® (CMS) is developing a new bag-valve-mask (BVM) designed to limit ventilation rates. The purpose of this study was to compare ventilation rates between a standard BVM device and the CMS device. Methods: This was a prospective, observational, semirandomized, crossover study using Army Medics. Data were collected during Brigade Combat Team Trauma Training classes at Camp Bullis, Texas. Subjects were observed during manikin simulation training in classroom and field environments, with total duration of manual ventilation and number of breaths given recorded for each device. Analysis was performed on overall ventilation rate in breaths per minute (BPM) and also by grouping the subjects by ventilation rates in low, correct, and high groups based on an ideal rate of 10-12 BPM. Results: A total of 89 Medics were enrolled and completed the classroom portion of the study, with a subset of 36 evaluated in the field. A small but statistically significant difference in overall BPM between devices was seen in the classroom (ρ < .001) but not in the field (ρ > .05). The study device significantly decreased the incidence of high ventilation rates when compared by groups in both the classroom (ρ < .001) and the field (ρ = .044), but it also increased the rate of low ventilation rates. Conclusion: The study device effectively reduced rates of excessive ventilation in the classroom and the field.