Environmental Engineering Reference
In-Depth Information
lammable.gases..Permanently.installed.containers.must.be.provided.with..substantial.
noncombustible.supports.on.irm.noncombustible.foundations.
Nitrous.oxide.piping.systems.for.the.in-plant.transfer.and.distribution.of.nitrous.
oxide.must.be.designed,.installed,.maintained,.and.operated.in.accordance.with.the.
Compressed.Gas.Association.pamphlet.G-8.1-1964.
Oxygen.cylinders.in.storage.must.be.separated.from.fuel-gas.cylinders.or.com-
bustible.materials.(especially.oil.or.grease).by.a.minimum.distance.of.20.feet.or.by.a.
noncombustible.barrier.at.least.5.feet.high.having.a.ire-resistance.rating.of.
1
/
2
.hour.
conFIned sPAces (29 cFr 1910.146)
Many.workplaces.contain.spaces.that.are.considered.conined.because.their.conigura-
tions. hinder. the. activities. of. employees. who. must. enter,. work. in,. and. exit. them.. For.
example,. employees. who. work. in. process. vessels. generally. must. squeeze. in. and. out.
through.narrow.openings.and.perform.their.tasks.while.cramped.or.contorted..OSHA.
uses. the. term. “conined. space”. to. describe. such. spaces.. In. addition,. there. are. many.
instances.where.employees.who.work.in.conined.spaces.face.increased.risk.of.exposure.
to.serious.hazards..In.some.cases,.coninement.itself.poses.an.entrapment.hazard..In.
other.cases,.conined.space.work.keeps.employees.closer.to.hazards,.such.as.asphyxiating.
atmospheres.or.the.moving.parts.of.machinery..OSHA.uses.the.term.“permit-required.
conined. space”. or. permit. space). to. describe. those. spaces. that. both. have. “conined.
space”.and.have.elements.that.pose.health.or.safety.hazards.(see.Figure 25.4).
Improper.entry.into.conined.spaces.has.resulted.in.approximately.200.lives.lost.
each.year..Conined.spaces.are.those.of.adequate.size.and.shape.to.allow.a.person.to.
enter.but.have.limited.openings.for.workers.to.enter.and.exit.and.are.not.designed.for.
continuous.human.occupancy..Examples.of.conined.spaces.are.storage.tanks,.silos,.
pipelines,.manholes,.and.underground.utility.vaults.
Conined. spaces. should. be. thoroughly. emptied. of. any. corrosive. or. hazardous.
substances,.such.as.acids.or.caustics,.before.entry..All.lines.to.a.conined.space.con-
taining.inert,.toxic,.lammable,.or.corrosive.materials.must.have.the.valve.off.and.
blanked.or.disconnected.and.separated.before.entry..All.impellers,.agitators,.or.other.
moving.parts.and.equipment.inside.conined.spaces.should.be.locked.out.and.tagged.
out.if.they.present.a.hazard.
In.evaluating.conined.space.accidents.in.the.past,.certain.scenarios.seem.to.con-
tinuously.occur..These.included.the.failure.to.recognize.an.area.as.a.conined.space;.
failure. to. test,. evaluate,. and. monitor. for. hazardous. atmospheres;. failure. to. train.
workers.regarding.safe.entry;.and.failure.to.establish.rescue.procedures..At.times,.
either.natural.or.mechanical.ventilation.is.enough.to.make.the.space.safe,.which.can.
be. provided. prior. to. conined. space. entry.. Appropriate. atmospheric. tests. must. be.
performed.to.check.for.oxygen.deiciency,.explosive.concentrations,.and.toxic.sub-
stances.in.the.conined.space.before.entry..The.atmosphere.inside.the.conined.space.
must.be.frequently.tested.or.continuously.monitored.during.the.conduct.of.work.
With.the.promulgation.of.the.“Permit-Required.Conined.Space.Entry”.standard.
(29.CFR.1910.146),.all.these.failures.are.addressed..First,.a.written.and.signed.permit.
is.required.prior.to.entry.if.the.space.contains.or.has.the.potential.to.contain.a.hazard-
ous.atmosphere.(e.g.,.oxygen.deicient,.lammable,.or.toxic);.if.it.contains.materials.
