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XI. Conclusions on Ignition Source and Explosion

The Panel concludes that there were two plausible ignition sources at the
time of the blowout: (1) engine rooms number 3 and/or number 6 (and associated
electrical switch gear rooms); or (2) the mud gas separator located near the rig
floor. The evidence that supports the Panel’s conclusion is discussed below.

A. Ignition Sources

The most probable ignition source was engine room number 3 and/or
number 6. The conclusion is supported by: (1) witness testimony; (2) the location
of the air intakes into the engine rooms; (3) engine and electrical switch‐gear
rooms that were unclassified areas with numerous potential ignition sources that
could initiate an explosion; (4) as a dynamically‐positioned rig, the Deepwater
Horizon may not have been designed to immediately shut‐down when high
levels of gas are detected; (5) the Panel found no evidence that the over‐speed
devices properly functioned and found evidence that such devices may not have
been inspected.

As mentioned previously in this Report, the hydrocarbon influx quickly
overwhelmed the mud gas separator. Witness testimony supports the fact that
there was a flash explosion near the air intake of engine room number 3 and the
mud gas separator shortly after the gas came onto the rig. The catastrophic
failure of the mud gas separator created a possible ignition source with the gas
plume released onto the rig from the well.

B. Contributing Causes of the Explosion

The air intake for engine room number 3 is located in the center of the
deck just aft of the rig floor, while the air intake of the engine room number 6 is
outboard on the starboard side of the rig aft of the rig floor. The Panel concluded
that the delayed explosion between engines number 3 and number 6 was due to

the difference in the distance between the air intakes and the gas flow. The
location of the air intakes for the engine room number 3 and number 6 was a
contributing cause of the Deepwater Horizon explosion.

The Panel found no evidence that the “rig saver” function of the over‐
speed devices successfully shut down engines 3 and 6. The failure of the over‐

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