HySafe Wiki | BRHS / Radiation Characteristics

In contrast to other hydrocarbon fuels, a hydrogen flame radiates significantly less infrared (IR) radiation (heat) and virtually no visible radiation (light). As a result, hydrogen burns with a pale blue, almost invisible flame that is almost visually imperceptible in artificial light or daylight.

However, in contrast to hydrocarbon flames, hydrogen flame also emits some limited amount of radiation in the ultraviolet (UV) region around 180 to 300 nm, which is exploited by UV detectors to detect hydrogen flame. Most UV detectors are made immune to solar sensitivity by using a sensing device only sensitive to the UV radiation below the 360-nm range. The lower radiation from a hydrogen flame makes the flame itself hotter than a hydrocarbon flame, and objects engulfed by a hydrogen flame tend to heat faster. However, the lower radiation of heat from the flame means that less heat is radiated to objects or people outside the flame.

The consequence of the almost invisible hydrogen flame is that the human physical perception of the heat from a hydrogen fire does not occur until direct contact with the combustion gases. This problem is often resolved by throwing a dry fire extinguisher or dust into the air that will cause the flame to emit visible radiation.

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