Hydrogen flames are almost invisible to humans, so thermal and optical sensors are used to detect burning hydrogen.
- To cover a large area or volume, many thermal detectors are needed and should be located at or near the site of a potential fire.
- Optical sensors for detecting hydrogen flames can operate in the ultraviolet or infrared spectral region. Closed-circuit infrared and ultraviolet remote-viewing systems equipped with appropriate filters have been used successfully.
- Linear heat detection systems, consisting of heat-sensitive polymer insulation and inner conductors, respond when a rated activation temperature is reached.
- Thermal (heat) detectors, installed in accordance with NFPA 72, can respond to either a fixed temperature or when a specified rate of temperature change occurs.
Flame detection systems are not required by NFPA 55, but NFPA 52 does require them for hydrogen fueling stations (i.e., hydrogen dispensing operations).
Flame detectors should be installed in certain applications (e.g., near hydrogen dispensers in hydrogen fueling stations). Detectors should provide a rapid and reliable indication of the existence, location, and size of a hydrogen flame.
If flame detection tools are not available, trained personnel may cautiously approach a suspected leak with an outstretched broom to detect the presence of a hydrogen flame.
Automatic and/or manual shutoff valves should be provided external to the laboratory storage unit, or other space so the flow of hydrogen can be stopped in an emergency situation.