Environmental Engineering Reference
In-Depth Information
tABle 23.4
recommended ratios of Illumination for various tasks
luminance ratios
conditions
ofice
Industrial
Between.tasks.and.adjacent.darker.surroundings
3:1
3:1
Between.tasks.and.adjacent.lighter.surroundings
1:3
1:3
Between.tasks.and.more.remote.darker.surfaces
5:1
20:1
Between.tasks.and.more.remote.lighter.surfaces
1:5
1:20
Between.luminaires.(or.windows,.skylights).and.surfaces.adjacent.to.them
20:1
NC
a
Anywhere.within.normal.ield.of.view
40:1
NC
a
a.
NC.means.not.controllable.in.practice.
exposure.limits.solely. on. preventing. thermal. problems.. In. the. meantime,. research.
continues..Use.of.RF/MW.radiation.includes.aeronautical.radios,.citizen's.band.(CB).
radios,. cellular. phones,. cooking. of. foods. in. microwave. ovens,. heat. sealers,. vinyl.
welders,.high-frequency.welders,.induction.heaters,.low.solder.machines,.communi-
cations. transmitters,. radar. transmitters,. ion. implant. equipment,. microwave. drying.
equipment,.sputtering.equipment,.glue.curing,.and.power.ampliiers.
Infrared. radiation. does. not. penetrate. below. the. supericial.layer.of. the. skin,. so.
that.its.only.effect.is.to.heat.the.skin.and.the.tissues.immediately.below.it..Except.for.
thermal.burns,.the.health.hazard.upon.exposure.to.low-level.conventional.infrared.
radiation.sources.is.negligible.
Visible. radiation,. which. is. about. midway. in. the. electromagnetic. spectrum,. is.
important.because.it.can.affect.both.the.quality.and.accuracy.of.work..Good.light-
ing. conditions. generally. result. in. increased. product. quality. with. less. spoilage. and.
increased.production..Lighting.should.be.bright.enough.for.easy.vision.and.directed.
so. that. it. does. not. create. glare.. Illumination. levels. and. brightness. ratios. recom-
mended.for.manufacturing.and.service.industries.are.found.in.Table 23.4
Ultraviolet. radiation. in. industry. may. be. found. around. electrical. arcs,. and. such.
arcs.should.be.shielded.by.materials.opaque.to.the.ultraviolet..The.fact.that.a.mate-
rial.may.be.opaque.to.ultraviolet.has.no.relation.to.its.opacity.to.other.parts.of.the.
spectrum.. Ordinary. window. glass,. for. instance,. is. almost. completely. opaque. to.
the.ultraviolet.in.sunlight;.at.the.same.time,.it.is.transparent.to.visible.light.waves..
A piece. of. plastic,. dyed. a. deep. red-violet,. may. be. almost. entirely. opaque. in. the.
.visible.part.of.the.spectrum.and.transparent.in.the.near-ultraviolet..Electric.welding.
arcs.and.germicidal.lamps.are.the.most.common,.strong.producers.of.ultraviolet.in.
industry..The.ordinary.luorescent.lamp.generates.a.good.deal.of.ultraviolet.inside.
the.bulb,.but.it.is.essentially.all.absorbed.by.the.bulb.and.its.coating.
The.most.common.exposure.to.ultraviolet.radiation.is.from.direct.sunlight,.and.
a.familiar.result.of.overexposure—one.that.is.known.to.all.sunbathers—is.sunburn..
Most.everyone.is.also.familiar.with.certain.compounds.and.lotions.that.reduce.the.
effects.of.the.sun's.rays,.but.many.are.unaware.that.some.industrial.materials,.such.
as.cresols,.make.the.skin.especially.sensitive.to.ultraviolet.rays..So.much.so.that.after.
