Assessment of effective ventilation in neonatal mask ventilation can be difficult. This study aims to determine whether manual ventilation with a T-piece resuscitator containing an inline CO2 detector (either a Pedi-Cap® CO2 detector or a Neo-StatCO2 <Kg® CO2 detector connected to a facemask) facilitates effective positive pressure ventilation compared to no device in a mannequin study. Paediatric and neonatal trainees were randomly assigned to determine which method they began with (no device, Pedi-Cap or a Neo-Stat). The participants used each method for a period of 3 min. They were video-recorded to determine the amount of effective ventilations delivered and the overall percentage efficiency of each method. Efficacy of ventilation was determined by comparing the number of manual ventilations delivered with the number of times chest rise was observed in the video recording. There were 19 paediatric trainees who provided a total of 7,790 ventilations, and 93% were deemed effective. The percentage of effective ventilations with the T-piece resuscitator alone, the PediCap and the NeoStat were 90, 94 and 96%, respectively. The difference was greatest in the first minute (T-piece resuscitator alone 87.5%, PediCap 94%, NeoStat 96%). Two thirds preferred the Neo-Stat. The use of a CO2 detector improves positive pressure ventilation in a mannequin model, especially in the first minute of positive pressure ventilation. The Neo-Stat CO2 detector was the preferred device by the majority of the participants.