Environmental Engineering Reference
In-Depth Information
Class.IIA.lasers.are.low-power.visible.lasers.that.emit.above.Class.I.levels.but.at.
a.radiant.power.not.above.1.mW..The.concept.is.that.the.human.aversion.reaction.to.
bright.light.will.protect.a.person..Only.limited.controls.are.speciied.
Class.IIIA.lasers.are.intermediate-power.lasers.(cw:.1.to.5.mW).and.only.hazard-
ous.for.intrabeam.viewing..Some.limited.controls.are.usually.recommended.
Class. IIIB. lasers. are. moderate-power. lasers. (cw:. 5. to. 500. mW. or. the. diffuse.
relection.limit,.whichever.is.lower)..In.general,.Class.IIIB.lasers.will.not.be.a.ire.
hazard,.nor.are.they.generally.capable.of.producing.a.hazardous.diffuse.relection..
Speciic.controls.are.recommended.
Class.IV.lasers.are.high-power.lasers.(cw:.500.mW.or.the.diffuse.relection.limit).
and.are.hazardous.to.view.under.any.condition.(directly.or.diffusely.scattered),.and.
are a. potential. ire. hazard. and. a. skin. hazard.. Signiicant. controls. are. required. of.
Class.IV.laser.facilities.
Accident. data. on. laser. usage. have. shown. that. Class. I,. Class. II,. Class. IA,. and.
Class IIIA. lasers. are. normally. not. considered. hazardous. from. a. radiation. stand-
point.unless.illogically.used..Direct.exposure.on.the.eye.by.a.beam.of.laser.light.
should.always.be.avoided.with.any.laser,.no.matter.how.low.the.power.
There.are.some.uses.of.Class.IIIB.and.Class.IV.lasers.where.the.entire.beam.path.
may.be.totally.enclosed,.the.beam.path.is.conined.by.design.to.signiicantly.limit.
access,.and.where.the.beam.path.is.totally.open..In.each.case,.the.controls.required.
vary.as.follows:
•.
Enclosed.(total).beam.path
•.
Limited.open.beam.path
Protective. equipment. (e.g.,. eye. protection,. temporary. barriers,. clothing. and/or.
gloves,. respirators,. etc.). is. recommended,. for. example,. only. if. the. hazard. analysis.
indicated.a.need,.or.if.the.Safe.Operating.Procedure.(SOP).requires.periods.of.beam.
access.such.as.during.setup.or.infrequent.maintenance.activities..Temporary.protec-
tive.measures.for.service.can.be.handled.in.a.manner.similar.to.the.service.of.any.
embedded.Class.IV.laser.
When.the.entire.beam.path.from.a.Class.IIIB.or.Class.IV.laser.is.not.suficiently.
enclosed.or.bafled.to.ensure.that.radiation.exposures.do.not.exceed.the.maximum.
permissible.exposure,.a.laser-controlled.area.is.required..During.periods.of.service,.
a.controlled.area.may.be.established.on.a.temporary.basis..Two.controls.are.required.
for. both. Class. IIIB. and. Class. IV. installations:. (1). posting. with. appropriate. laser.
warning.signs,.and.(2).operated.by.qualiied.and.authorized.personnel.
Control.measures.recommended.for.Class.IIIB.and.required.for.Class.IV.lasers.
are.as.follows:
•.
Supervision.directly.by.an.individual.knowledgeable.in.laser.safety:.entry.
of.any.noninvolved.personnel.requires.approval.
•.
A.beam.stop.of.an.appropriate.material.must.be.used.to.terminate.all.poten-
tially.hazardous.beams.
•.
Use.diffusely.relecting.materials.near.the.beam,.where.appropriate:.appro-
priate.laser.protective.eyewear.must.be.provided.to.all.personnel.within.the.
laser.controlled.area.
