2025 Center for Hydrogen Safety Asia-Pacific Conference
What Colour Are Hydrogen Flames?
Author
It is widely reported that hydrogen flames can be difficult to see, thus presenting a hazard whereby individuals could inadvertently come in contact with a naked flame. Whether because of a hydrogen fire, or as part of normal appliance operation, the different flame appearance of hydrogen compared with natural gas will be important for consumer acceptance and could present a safety barrier in the application of residential appliances in a domestic setting. Albeit inconsistently reported, many reference sources state a definitive colour; however, hydrogen flames can be almost any colour of the rainbow. Understanding the flame colour is important, but more critical to ensure safety is whether the flame is clearly visible, and under which conditions it is not reliably detectable by eye. The objective of this work was to isolate and quantify the factors that may influence hydrogen flame visibility, and to determine if flame visibility can be relied upon as an indicator of flame presence in a similar way that natural gas flames are expected to be visible in a domestic setting. A series of experimental testing was performed to assess visibility under real-world conditions. The outcomes highlight that making a safety assessment using conventional descriptions of flame appearance is not recommended because of uncontrolled factors in practical settings.