Explosion in Microbiological Anaerobic Chamber -

A microbiological anaerobic chamber containing a flammable mixture of hydrogen and air exploded. A fire followed the explosion, but was rapidly extinguished by staff using fire extinguishers, prior to the arrival of fire service personnel. The pressure wave from the explosion damaged neighbouring building and caused an injury.

The INITIATING CAUSE was the erroneous admittance of air to the chamber during maintenance. The hydrogen-enriched atmosphere in the chamber mixed with air.
Most likely, the IGNITION SOURCE was the oxidation catalyst in the chamber.

The local operating procedures used in the lab allowed high concentrations of hydrogen to be introduced into the chamber. A component of the ROOT CAUSE was the error of a lab worker.

Microbiological Anaerobic Chamber

An unknown concentration of hydrogen was present in the chamber, presenting a significant fire and explosion risk. The incident occurred during maintenance.

DESCRIPTION OF THE PROCESS
Mixtures of inert gases and hydrogen are intended to be routinely used in the type of anaerobic chamber involved in the incident. The mixtures used in the chamber involved were produced locally in the laboratory using nitrogen, carbon dioxide, and hydrogen. The hydrogen in the mixture reacts with any oxygen present in the chamber, on a heated catalyst, to eliminate oxygen and keep the chamber anaerobic.

a user of the chamber was taken to hospital by ambulance to have burns treated. They have subsequently fully recovered from their injuries. Another worker in the lab at the time required medical observation but was otherwise unharmed.

The pressure wave from the explosion blew windows out of the laboratory, with glass hitting a passer-by on a path outside, and glass shards landing up to 30 m away. Ceiling panels were dislodged in the laboratory and adjacent rooms.

After the explosion there was a fire that was rapidly extinguished by staff using fire extinguishers, prior to the arrival of fire service personnel.

H2TOOLS report states the following:
"The practice of making gas mixtures in the laboratory should be eliminated, and gas mixtures with a known low hydrogen concentration should be purchased for use.
The concentration of hydrogen used should be such that it is not possible to form an explosive mixture on dilution with air. "

H2TOOLS further suggests the installation of gas detectors to monitor continuously O2 and H2 concentrations in the chamber.
Finally, it requires as well to ensure awareness and in-depth knowledge of all hazards and risks for all that laboratory workers.