An individual inadvertently connected a pure hydrogen gas bottle to a chamber/glove box as opposed to a 10% hydrogen (in nitrogen) bottle that should have been used. [The wrong bottle had mistakenly been delivered, and the inexperienced individual did not know the difference.] The hydrogen concentration increased within the chamber to about 9%. Since there was insufficient oxygen in the chamber to support combustion, the hydrogen did not burn, and was quickly diluted with nitrogen.
This incident led to several changes in procedure:
The purity of any gas bottle connected is double-checked. The practice outlined in the SOP requires confirming the content of the cylinder via the cylinder label prior to connection to the glove box. Increased attention is now paid during training of new staff members to ensure that this procedure is well understood.
The vacuum pump is kept off so that the dilute gas will mix with the hydrogen
Alarms are set at 10% hydrogen and at 300 ppm oxygen.
A new SOP has been written.