Account of Incident: Following a total site power
loss, the plant wide instrument air (IA) system
was switched over to nitrogen back-up. The
design was such that in this condition, nitrogen
could build up to an extent inside the analyser houses (AHs) on the original units, and to dangerous levels inside AHs
associated with a 1998 project.
Preventive precautions designed to protect against
the hazard in the original AHs (posting warning
signs, locking doors and returning keys to the Shift
Superintendent) to safeguard the AHs were not
completed. A warning announcement of IA status
was made over site radio to the on-site team in lieu
of the safeguards.
Preparing for restart later that day, the operations
team asked for analyser technician support to help
with reinstatement activities. The analyser
engineer (AE), and technician (TECH), arrived
on site the following day  at around
00:00hrs and 01:35hrs respectively. They met and
agreed their work plan; AE asked TECH to
wait for him in the control room and went to
complete an unrelated task for the ops team.
On return AE found that TECH had left the
control room and he set out to find him. At around
02:20hrs, AE discovered TECH apparently
unconscious in analyser house 1 (AH-1). He raised
the alarm having removed TECH from the analyser
house. The site first aider attempted to resuscitate
TECH but was unsuccessful;   TECH was
pronounced dead at hospital at 02:50hrs.
The likely cause of death was hypoxic hypoxia i.e.
asphyxiation through nitrogen, which resulted when
TECH entered AH-1. At that time, AH-1 would
have contained a nitrogen rich atmosphere as
demonstrated by a simulation of the events.
What Went Wrong:
There were three main factors that contributed to
this fatal accident:
1. The instrument air system supply was switched
over to nitrogen without confirmation that the
required safeguards were in place;
2. No-one briefed AE or TECH when they
arrived at site that the IA system supply had
been switched over to nitrogen;
3. The 1998-built analyser houses had IA purges
that discharged inside the analyser houses
rather than outside, giving more potential for
nitrogen-rich atmosphere internal to the AHs on
switchover of IA to nitrogen back-up.
Management of Change: the
changeover of instrument air supply to nitrogen
was not managed according to procedure.
Corrective Actions: Company  had already trained

staff in the potential hazards of nitrogen at site.
They have implemented actions to address causes
of this incident including:
- disabling nitrogen back-up of IA and suspension
of all permit exemptions until a review of hazards
is completed and measures are in place to
eliminate, control or mitigate them;
- putting in place a log-in and briefing procedure to
ensure hazards are communicated to all staff
going out on site;
- developing a tool to ensure that shift team
competence is maintained at all times for all
potential situations, and
- introducing a formal competence framework for
shift supervisory staff, and retrospectively
applying the qualifications and certification
process to all technicians.
Additional longer-term actions are planned to:
- confirm that the design of all AHs and similar
confined spaces comply with applicable industry
standards, and provide any necessary input to the
appropriate standards;
- review emergency procedures so as to be fit for
purpose in real life situations, and include
operational scenarios in the emergency exercise
plan so that teams are familiar with procedures;
- identify and translate critical procedures into
the local language, to facilitate understanding and
communication.
Key Messages:
- Treat nitrogen with great care, especially
where there is the possibility of build-up;
confirm that existing analyser houses
and other confined spaces comply with
current applicable design standards.
- Team and individual competence are
essential to managing plant safely,
especially during abnormal conditions.
- Communication across teams at a site is
particularly important to ensure common
awareness of the plant state and
potential hazards.