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X. Ignition Source(s) and Explosions

Two explosions occurred almost immediately after the blowout when the
large gas plume that had developed over the rig came in contact with one or
more ignition sources on the rig. The Panel considered the following possible
sources of ignition: (1) main engines and engine switch gear rooms; (2) mud gas
separator; (3) electrical equipment in hazardous areas; (4) friction and mechanical
sources; (5) non‐hazardous area sources; and (6) electrostatic discharge.

It is not possible to determine with certainty the source of ignition because
much of the physical evidence relevant to making such a determination was lost
with the rig or otherwise is not available. Based upon its review of witnesses
testimony and other evidence, the Panel concluded that the main engines (and
switch gear rooms) and the mud gas separator were the most likely ignition
sources.

A. Main Engines and Engine Switch Gear Rooms

1. Configuration of Engine Rooms on the Rig

The Deepwater Horizon had six engines located on the third deck of the rig.
Each engine was in an engine room that was equipped with air intake systems.
Each air intake system drew air from vents located in the engine room in which it
sat. Each engine room had an engine switch gear room attached to it.

The Deepwater Horizon’s engine rooms and switch gear rooms were
located in “unclassified” areas, which were areas that did not require explosion‐
proof enclosures, intrinsically‐safe equipment, and/or purged and pressurized
equipment. The engines and switch gears in the non‐classified areas were not
designed or tested to ensure that they would not initiate an explosion.

The engines had multiple redundant safety systems and shutdown

devices designed to shut down the engines in an over‐speed situation. Engine
over‐speed is a condition where an engine’s revolutions per minute (“rpms”)
exceed their normal operating speed. This condition can occur when
combustible gas is drawn into the intake system. To prevent this, the air intake
systems included a shut‐off device (sometimes referred to as a “rig saver”) that

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