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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

Flammability Limits - Mixtures

Is there a reference that quantifies the effects of pressure and temperature on the flammability limits of hydrogen/oxygen mixtures?

H2-air flammability limits vary with temperature  . The H2-air lower flammability limit is virtually the same as the H2-O2 lower limit. However, the H2-O2 upper flammability limit increases substantially to about 95% at room temperature and gets even higher at elevated temperatures.

 

FAQ Category
Submission Year
2024
Month
04

Auto-ignition

We are working on a project using hydrogen at 600 kPa (87 psi). How is the auto-ignition temperature of hydrogen as a function of pressure determined?

A pressure of 600 kPa (87 psi) is relatively moderate, so the combustion properties are similar to those at atmospheric pressure where the autoignition temperature of hydrogen is 585°C. 

FAQ Category
Submission Year
2024
Month
04
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