Environmental Engineering Reference
In-Depth Information
events.and.conditions.are.recorded.on.removable.tack.or.adhesive.notes.and.afixed.
sequentially.to.the.wall.in.a.conference.room.or.command.center..Because.the.exact.
chronology.of.the.information.is.not.yet.known,.using.removable.notes.allows.inves-
tigators. to. easily. change. the. sequence. of. this. information. and. to. add. information.
as.it.becomes.available..Different-colored.notes.can.be.used.to.distinguish.between.
events. and. conditions. in. this. initial. manual. construction. of. the. events. and. causal.
factors.chart.
If.the.information.becomes.too.dificult.to.manipulate.manually,.the.data.can.be.
entered. into. a. computerized. analysis. program.. Using. specialized. analytical. soft-
ware,.investigators.can.produce.an.events.and.causal.factors.graphic,.as.well.as.other.
analytical.trees.or.accident.models.
Whether.using.a.manual.or.computerized.approach,.the.process.begins.by.chron-
ologically. constructing,. from. left. to. right,. the. primary. chain. of. events. that. led. to.
the.accident..Secondary.and.miscellaneous.events.are.then.added.to.the.events.and.
causal.factors.chart,.inserted.where.appropriate.in.a.line.above.the.primary.sequence.
line..Conditions.that.affect.either.the.primary.or.secondary.events.are.then.placed.
above.or.below.the.events.
C
HArting
s
ymbols
Events.should.be.placed.in.a.rectangle.and.connected.by.arrows..The.Primary.Event.
Chain.should.be.connected.by.bold.arrows.and.directed.to.the.accident..Conditions.
should.be.placed.in.ovals.and.connected.by.dashed.arrows..Any.event.or.condition.
that.is.presumptive,.meaning.the.investigative.team.is.not.sure.whether.or.not.it.has.
any.effect.on.the.accident,.or.cannot.prove.that.it.has.occurred,.or.is.related.to.the.
accident,. should. placed. in. dashed. rectangles. (events). or. dashed. ovals. (conditions).
and.connected.by.dashed.arrows..Secondary.events,.like.primary.events,.should.be.
placed.in.a.rectangle.and.connected.by.arrows..However,.when.charting.the.second-
ary.events,.they.must.be.on.a.different.level,.either.above.or.below.the.Primary.Event.
Line;. this. will. help. reduce. confusion. on. which. events. are. primary. and. which. are.
secondary..An.example.of.an.Event.Factor.Chain.is.shown.in.Figure 9.3..A.narrative.
that.relates.to.the.accident.and.Figure 9.3.follows.
A.large.2,400-volt.fan.system.blew.a.fuse..The.electrician.obtained.a.fuse.from.
the.storeroom,.tagged.out.the.switch,.and.replaced.the.fuse..The.system.would.
not.work,.so.the.electrician.bypassed.a.safety.interlock.and.used.a.meter.to.check.
the.fuse..A.large.ireball.erupted,.causing.burns.that.required.hospitalization.and.
50.lost.workdays.
This. was. classiied. as. an. off-normal,. personnel. safety. occurrence. (in-patient.
.hospitalization).. However,. because. this. was. a. near. fatality. and. because. there.
existed.a.potential.for.signiicant.programmatic.impact,.the.investigation. used.
formal.Cause.and.Effects.Analysis.with.charting.to.identify.all.the.contributing.
conditions. and. any. weaknesses. in. programmatic. or. operational. control.. A.
condensed. version.of.the.working.chart.is.given.in.Figure 9.3..The.signiicant.
.indings.are.given.below.
