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Risk of fire when a person uses metallic tools inside a fume

Is there a big risk of fire when a person uses metallic tools inside a fume?

Using tools inside a fume hood that may have a flammable gas mixture should be prohibited. A properly operating hood of the right capacity should keep the mixture of hydrogen in air inside the hood below the Lower Flammability Limit (LFL) of hydrogen further reducing any risk. 

If the use of tools is necessary, the source of hydrogen should be isolated before the work begins even if the concentration of hydrogen is expected to be below the LFL. It is best practice to leak test equipment before introducing hydrogen to minimize the probability of leaks. If spark resistant tools are suitable for a specific task for working with hydrogen systems, use of such tools will lower the probability of producing a spark. 

FAQ Category
Submission Year
2023
Month
09

Environmental concerns about hydrogen venting from experiments

Any environmental concerns about hydrogen venting from experiments?

The key concern with any hydrogen release is the risk of creating a flammable mixture. There should be no environmental issues if you properly vent hydrogen to a safe area where it is diluted in air below the flammability limit before contacting an ignition source. Very small quantities of hydrogen are frequently releasing into a fume hood. Releases have to be small enough so that the vent air is sufficient to dilute to below the lower flammability limit. The fume hood face velocity should be in excess of 100 ft/min (30 m/min). 

Larger quantities of hydrogen should be released through a properly designed and constructed hydrogen vent stack. Standards and codes such as CGA G 5.5 and NFPA 2 provide guidance for vent stack design and installation.

FAQ Category
Submission Year
2023
Month
09

Hazards with hydrogen blend in air

Is there a hazard using a 4/96% hydrogen/nitrogen blend if it is released to the air?

If the concentration of hydrogen is less than the Lower Flammability Limit (LFL) of 4% in an inert gas, it is unlikely that a leak of this gas mix will form a flammable mixture as it dilutes into air. For example, industry uses ‘forming gas’, a mixture of 4 to 5% H2 in nitrogen, as an oxide reducing agent in materials processing furnaces and soldering operations. This mixture can also be used in conjunction with a hydrogen detector for leak testing gaseous hydrogen equipment.

FAQ Category
Submission Year
2023
Month
09
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