When we think about the hazards of electrolyzer systems, we tend to focus on the hydrogen hazard without giving sufficient thought to the other atom in H2O: Oxygen. In an electrolyzer system, the oxygen produced can pose its own set of hazards, while also compounding the hydrogen combustion risk. This presentation will provide a different perspective to electrolyzer safety by focusing on the oxygen hazard, best practices for oxygen safety, and analyzing lessons learned from prior incidents.