Radiation and Lasers

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Radiation and Lasers

• Carter J. Kerk, PhD, PE, CSP, CPE
• Industrial Engineering Department
• IENG 341 - Industrial Hygiene
• South Dakota School of Mines

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Assignment

• Read Chapter 10 Ionizing and Non-Ionizing
  Radiation
• Critical Thinking Questions
• p. 241
• 1 4
• Due?

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Introduction

• Radiation Control for Health Safety Act of 1960
• Several government standards
• OSHA
• CPSC
• FDA
• Consensus standards

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Non-Ionizing Radiation

• There are many sources of radiant energy sun,
  fire, microwaves, radio transmissions, atomic
  reactors, lamps, lasers.
• It takes 10 12 eV or more to break the bond of
  molecular elements. Sources of radiant energy
  below this level are considered non-ionizing.
• Sources above this level are considered
  ionizing. Ionizing radiation is any
  electromagnetic or particulate radiation capable
  of producing ions when it interacts with atoms or
  molecules.

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Types of Non-Ionizing Radiation

• Microwaves
• Ultraviolet Radiation
• Infrared Radiation
• High Intensity Visible Light
• Lasers
• VDTs
• Low Frequency Electric and Magnetic Fields
• lt 60 Hz ELF (Extremely Low Frequency), normally
  near high voltage transmission lines
• Cell Phones

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Electromagnetic Spectrum
Electromagnetic Spectrum contains all the wave
energies that allow modern conveniences such as
cellular phones, medical x-rays, pagers, TVs, and
radios to operate.
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Hazards of Non-Ionizing Radiation

• Although energy levels do not affect molecular
  structure, non-ionizing radiation can affect
  biological tissue by changing energy levels in
  tissue molecules, often producing heat
• Heat easily effects certain tissue
• Eye has little blood circulation and little
  ability to remove heat through blood flow

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Absorption properties of the eye for
electromagnetic radiation
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Microwaves

• Uses Communication, navigation, medical
  diathermy, microwave ovens, drying equipment
• Frequencies 30 MHz 300 GHz
• Wavelengths 1 mm 10 m
• Waves lt 3 cm are absorbed in outer skin
• 3 10 cm penetrate from 1 mm 1 cm
• 25 200 cm penetrate to deeper tissues organs
• gt 200 cm, human tissue is transparent
• Absorbed radiation is primarily converted to
  heat, possibly to hazardous levels
• Greatest danger eyes cataracts, some
  pacemakers

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Microwave Controls

• Limit exposure and/or intensity
• Distance from source
• Shielding

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MicrowaveMeasurement Standards

• Measure microwaves with thermal or electrical
  detector instruments
• OSHA 29 CFR 1910.97
• Limit power density to 10 mW/cm2 for exposures gt
  0.1 hr
• For lt 0.1 hr, limit energy density to 1 mW-hr /
  cm2

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Microwave Standards

• ACGIH publishes limits

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Lasers

• LASER acronym for Light Amplification by
  Stimulated Emission of Radiation
• Intense, coherent, directional optical radiation
• Consists of an energy source, resonant cavity,
  and an active laser medium
• An assembly of electrical, mechanical, and
  optical components
• Becoming increasingly common welding,
  machining, measuring, alignment, checkout
  scanners, printers, medical applications, etc.

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Laser Hazards

• Some lasers are very dangerous and others not at
  all
• Hazard depends on intensity, wavelength, duration
  of exposure, and body part exposed
• With high energy levels, heat builds causing
  combustion

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Laser Hazards

• Lasers can fall in visible, ultraviolet and
  infrared ranges
• Greatest danger is visible range

The optical spectrum. Laser light is nonionizing
and ranges from theultra-violet (100 - 400nm),
visible (400 - 700nm), and infrared (700nm -
1mm).
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Laser Hazards

• The eye is most vulnerable
• The cornea (the clear, outer surface of the eye's
  optics) does not have an external layer of dead
  cells to protect it from the environment.
• Light entering the eye from a collimated beam is
  concentrated by a factor of 100,000 times when it
  strikes the retina

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Safety Standards

• American National Standards Institute's Z136
  series of laser safety standards.
• These standards are the foundation of laser
  safety programs in industry, medicine, research,
  and government.
• The ANSI Z136 series of laser safety standards
  are referenced by the Occupational Safety
  and Health Administration (OSHA)
• Provides information on how to classify lasers
  for safety, laser safety calculations and
  measurements, laser hazard control measures, and
  recommendations for Laser Safety Officers

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Controlling Laser Hazards

• Engineering Controls (most reliable)
• Protective housings and interlocks, protective
  filter installations, key-controls, and system
  interlocks
• Administrative Controls
• Standard operating procedures
• Facilities using Class 3b or Class 4 lasers or
  laser systems should designate a Laser Safety
  Officer

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Assignment

• Read Chapter 10 Ionizing and Non-Ionizing
  Radiation
• Critical Thinking Questions
• p. 241
• 1 4
• Due?