The role of sodium on hydrogen flame visibility in domestic settings

This study investigates the factors influencing the colour and visibility of hydrogen flames in domestic settings, where flame visibility is an important safety control, particularly in cooktop applications. Controlled laboratory experiments and field measurements were conducted to isolate key variables. Results show hydrogen flames are predominantly orange due to sodium emissions, primarily originating from sea salt aerosols in ambient air. This sodium-driven luminosity was found to be correlated to flame brightness, but variable depending on environmental conditions, particularly wind direction. Winds that had passed over the ocean increased flame visibility, while filtered air reduced luminosity, rendering flames nearly invisible under typical lighting. Blue and red emissions were visible only under low-light conditions. Comparative tests confirmed that hydrogen flames are less visible than natural gas flames, even under favourable conditions. The findings demonstrate that hydrogen flame visibility is inconsistent and cannot be reliably used as a safety indicator in domestics applications.