Three men inside a reactor vessel experienced breathing difficulties.
They had inhaled vapour containing 1,1,1-trichloroethane as a result of
using a cleaning agent in a poorly ventilated confined space. The three
men were taken to hospital for observation and tests. They were
discharged on the day following the incident and returned to work fully
recovered two days later.The incident resulted from using a hazardous
cleaning solvent in an inadequately ventilated confined space. The
solvent contained 1,1,1-trichloroethane a harmful substance which should
not be inhaled. In addition to the air flow being inadequate to
effectively dilute the solvent vapours, the direction of ventilation was
wrong. For this heavier than air vapour the air flow should have been
from the top downwards.
Lessons
1. No cleaning agents containing solvents should be used in restricted
spaces - such as tankers, columns, reactors, large pipelines etc. For
the weld testing, water should be used instead of solvent based agents.
Investigations should take place as to whether a harmless test process
could be used instead of the dye disclosure method.
2. When using a solvent based cleaner, adequate air supply and
ventilation should be ensured. If the fumes are heavier than air, they
should be extracted from below.
3. If the ventilation is insufficient, independent breathing apparatus must be used.
4. If possible, work should not be carried out on a vessel at the same
time as work in the vessel. If this is unavoidable, the persons working
inside should be informed of the nature and scope of work being carried
out on the outside. We should also check that safety measures governing
work in tanks are adequate. A special co-ordinator is required for this.
5. On medical recommendation, various medications should be kept on
site, such as Folon A 200 mg injection ampules and Auxilosan measured
dose aerosols.
6. All jobs should be carefully planned from beginning to end.
Deviations from the plan should require formal authorisation at a high
level. Existing work permits should be withdrawn and new permits issued
to cover the change in scope. There is a tendency to take less care
towards the end of a job as the pressure to recommission plant and
equipment increases.
7. The site policy on the use of solvents (and other hazardous
chemicals) should be made absolutely clear to everyone who could be
affected by their use. Inherent methods of enforcement of the policy
should be devised. e.g. if particular solvent based cleaners are not
allowed on site the purchasing system should prevent orders for them
from being processed.
Source:ICHEME
