Introduction: Out-of-hospital cardiac arrests are an important public healthcare problem in Europe. Survival after such an event greatly depends on the actions of bystanders. In the last decade, a lot of research has been investigating whether rescue breaths should remain part of the basic life support (BLS) algorithm, due to complexity of the technique and questionable effects on survival. The readiness of lay providers to deliver rescue breaths and effects of the use of barrier devices on the quality of delivery of rescue breaths and BLS are less investigated. Purpose: We wanted to evaluate the use of simple face shield during BLS by lay providers and the impact of the use of a simple face shield on the overall quality of cardiopulmonary resuscitation. Methods: Our research strategy was a cross-sectional study. Data were collected during resuscitations at five ambulance stations in Slovenia, an anonymous online questionnaire and using measurements on resuscitation manikins during practical first aid training of students. Results: In the analysed 123 resuscitations bystanders did not use a simple face shield. An online questionnaire was completed by 473 participants (314 of them were laypeople). Only a good third of lay participants knew the correct ratio of chest compressions and rescue breaths in adult BLS. Fifty-three per cent knew that a simple face shield is part of the first aid kit in vehicles. However, in a theoretical resuscitation scenario in the online questionnaire, this did not have a significant effect on the willingness to deliver rescue breaths. Relationship between the victim and the bystander is an important factor in the willingness to deliver rescue breaths. Using measurements from the resuscitation manikin, we found a statistically significant increase (p < 0,001) in the time from the incident to the start of BLS when using a simple face shield and a shorter time of chest compressions, expressed as a fraction of the time of BLS. On the other hand, the use of simple face shield statistically significantly (p < 0,005) increased the rate of correct rescue breaths and decreased the rate of excessive rescue breaths. Discussion and conclusion: In Slovenia, a simple face shield is a relatively well-known barrier device, but is rarely used during the delivery of rescue breaths. As we have found that the use of simple face shield decreases the quality of BLS, it would be more sensible to focus on the quality of rescue breaths rather than the use of simple face shield during first aid courses. Courses and training might benefit from including discussions about factors that encourage and discourage bystanders to provide first aid.