Social robots have been shown to effectively promote healthy behaviour in humans. In the context of the pandemic, these robots have been used to encourage the use of face masks and other bio-safety measures. However, human perception in these scenarios is yet to be assessed. This study evaluates the effectiveness of using a social robot, specifically the NAO robot, to promote face-mask usage in public spaces with a hybrid experiment. The methodology involves an in-person study, as well as an online survey. The results show that the robot was able to detect correct face-mask usage with 95% accuracy, and 87.5% of participants had a positive experience interacting with the robot. Statistical results also suggest that the users perceiving a human-robot interaction scenario through a pre-recorded video can perceive differently the robot's trust, safety, and intelligence, among others. These findings suggest that social robots can be a valuable tool for promoting health and safety measures, not only during the pandemic but in other collaborative environments as well.