The design objective is to ensure that detection occurs immediately and operating personnel are notified as appropriate if hydrogen leaks into the atmosphere or a hydrogen fire occurs. Recall that gaseous hydrogen is colorless and odorless, the flame without contaminants is difficult to see, and it radiates little heat. Considerations for gas and flame detector use include:
Location - The number and distribution of detection points and time required to shut off the hydrogen source should be based on factors such as leak rates, ventilation rates, and the volume of space in the laboratory. Locations to consider include:
- Permanent installations in indoor storage facilities
- Critical locations where leaks may occur (typically immediately above or where flow is concentrated) during experiments or the operation of processes involving hydrogen
- Where hydrogen may accumulate.
Response Time - Evaluate the expected response time of the detection system to ensure compatibility with the required response of the safety system or provision.
Alarms - Detection signals should actuate warning alarms and actuate shutdown actions whenever practical. Audio and visual alarms should be provided as necessary.
Inadvertent Ignition - The hydrogen detection system should be compatible with other systems such as fire detection and fire suppression. The detection units should not be ignition sources.
Areas Without Detection - Portable hydrogen leak and flame detectors (e.g., thermal imaging camera or handheld flammable gas detector) should be available if permanent detectors are not installed.
- Always allow enough time for troubleshooting/debugging a monitoring system before it's used.
- Use inert gas and bubble indicators (soap in water) to identify leaks during system/vessel checkout. Use of helium leak detectors for smaller leaks is recommended if available.
- Piping and equipment leak checks with both soap solution and helium should be done before allowing any hydrogen to enter the system.
- Always inert a system with suspected leaks and then top-off with a detectable gas when using a flammable gas leak detector for leak detection. Aim to keep hydrogen contents in systems undergoing leak checking to less than 5% inert gas.
Maintenance - Fire and gas detection systems should be given regular calibrations.