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Janet M. Gutiérrez, DrPH, CHP, RRPT Radiation Safety Program Manager

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1 Ionizing & Non-ionizing Radiation ENGR 4410 – INDUSTRIAL HYGIENE INSTRUMENTATION October 23, 2013
Janet M. Gutiérrez, DrPH, CHP, RRPT Radiation Safety Program Manager Environmental Health & Safety

2 Speaker Biography Janet M. Gutierrez is manager of the Radiation Safety Program at The University of Texas Health Science Center at Houston. She is a Certified Health Physicist (CHP) and a Registered Radiation Protection Technologist (RRPT). In August 2011, she received a Doctorate in Public Health from the The University of Texas at Houston School of Public Health (UT SPH), and in 2005, she received a M.S. in Environmental Sciences / Industrial Hygiene from UT SPH as well. In 1998, Janet received a B.S. in Radiological Health Engineering from Texas A&M University in College Station, TX.

3 Speaker Biography Travis Halphen is a Safety Specialist in the Radiation Safety Program at The University of Texas Health Science Center at Houston (UTHSC-H). He is currently seeking his MPH in Environmental Health and Occupational Safety from University of Texas School of Public Health (UT SPH) and on May 2006 he received a Bachelors in Medical Physics from Louisiana State University. He was Assistant Radiation Safety Officer and Laser Safety Officer at Kansas State University from 2006 to 2008 before he ended up at his current position at UTHSC-H

4 Ionizing vs. Non-ionizing Radiation
Electromagnetic Spectrum Nonionizing radiation is greater than 100 nm in wavelength

5 Radiation

6 Ionizing & Non-ionizing Radiation
Units Decay Inverse Square Law Shielding, HVL, TVL Instruments Dosimetry Biological Effects Regulations Practice Problems Types Biological Effects Regulations/Guides

7 What is Radiation? Radiation is energy transmitted by particles or electromagnetic waves Radiation can be ionizing or non-ionizing

8 Basic Concepts Radiation: energy
Ionizing vs. Non-Ionizing: enough energy to eject orbital electrons Radioactivity: excess nuclear energy

9 Radioactivity Radioactivity is the natural property of certain nuclides to spontaneously emit energy, in the form of ionizing radiation, in an attempt to become more stable.


11 Basic Concepts Radionuclide Nuclide
Isotopes have the same Z and a different A; 10C,11C, 12C, 13C, 14C Isobars have the same A and a different Z; 14N, 14O; 15N, 15C Isomers have the same A and the same Z; 99mTc, 99Tc Isotones have the same N and a different A; 14O,13N,12C,11B,10Be,8Li

12 Basic Concepts Types of radiation: Alpha: particulate, massive
Beta: particulate, penetrating Gamma: electromagnetic, penetrating X-ray: electromagnetic, penetrating Neutron: particulate, no charge

13 Alpha (α) Needs at least 7.5 MeV energy to penetrate nominal protective layer of skin (7 mg/cm2) Most α less than this energy, so can not penetrate skin Range in air Range (cm) = 0.56E for E< 4 MeV Range (cm) = 1.24E for E> 4 MeV

14 Beta (β) Need at least 70 keV energy for beta to penetrate nominal protective layer of skin βave = 1/3 βmax Range in air Range is ~ 12 ft / MeV Bremsstrahlung for high energy beta & high Z material Ex. P-32 and Lead

15 Gamma (γ) Photoelectric Compton Scattering Pair Production Photon
X-ray Gamma ray

16 Neutrons (n) Often expressed in n / cm2sec (flux)
Thermal neutrons = eV Slow neutrons = 1 eV – 10 eV Fast neutrons = 1 MeV – 20 MeV Relativistic neutrons = > 20 MeV U-238 & U-235

17 Shielding Examples

18 Shielding for Multiple Types of Radiation
High Energy Betas Bremstrahlung Neutrons Gammas

19 Units Activity: Curie (Ci) 3.7 x 1010 disintegrations per second
SI: Becquerel 1 dps Exposure: Roentgen SI: C/kg Absorbed Dose: Rad (Roentgen Absorbed Dose) SI: Gray, 1Gy = 100 Rad Risk: Rem (Roentgen Equivalent Man), Rad x QF SI: Sievert, 1 Sv = 100 Rem

20 Quality Factors

21 Half-life Half-life - the amount of time required for 1/2 of the original sample to decay The half-life is constant for each radionuclide and varies due to the nuclear structure.

22 Radioactive Decay Is the process by which the amount of activity of a radionuclide diminishes with time. Examples:

23 Radioactive Decay Formula
Variables A  Activity at time t A0  Original Activity t  Time   Decay Constant T1/2 Half Life Constants ln 2  e1 

24 Concepts Radioactive Decay: A = Aoe-λt Inverse Square Law
A = λN λ = / T1/2 Inverse Square Law Shielding I = IoBe-t

25 Annual US Average Dose from Background Radiation was
Total US average dose equivalent = 360 mrem/year Total exposure Man-made sources Radon Internal 11% Cosmic 8% Terrestrial 6% Man-Made 18% 55.0% Medical X-Rays Nuclear Medicine 4% Consumer Products 3% Other 1% 11%

26 Annual US Average Dose from Background Radiation Now is 625 mrem
National Average Dose is US is 625 mrem, with medical being the largest type of increase.

27 Ionization of Gas – Radiation Detector
A = recombination B = ionization C = proportional D = limited proportional E = Geiger Muller F = continuous discharge

28 Monitoring Instrumentation Gas filled Solid scintillator
Liquid scintillation

29 Monitoring Dosimeters Film badges: beta, gamma, x-ray
Permanent record Subject to fading Thermoluminescent dosimeter (TLD): beta, gamma, x-ray No permanent record Can be used for long term use Pocket ion chamber: gamma, x-ray Immediate readout Shock sensitive

30 Biological Effects Radiation Effects on Cells:
Somatic (early, delayed) & Genetic Dose Responses Linear, Linear Quadratic, Threshold

31 Stochastic and Non-stochastic Effects
Dose increases the probability of the effect No threshold Any exposure has some chance of causing the effect Cancer Non-stochastic effects Dose increases the severity of the effect Threshold Effects result from collective injury of many cells Reddening, cataract, skin burn Stochastic: Chance/Probability (cancer) Non-stochastic: Related directly to dose - acute (burns, reddening)

32 Biological Effects Assumptions Used for Basis of Radiation Protection Standards No Threshold Dose, Risk with Given Dose Increases With Increasing Dose Received, Acute vs. Chronic Exposures Not Considered, i.e. Repair

33 Biological Effects Prenatal Exposures
Law of Bergonie & Tribondeau (1906): Cells Tend to be Radiosensitive if They Have Three Properties: A) Have a High Division Rate B) Have a Long Dividing Future C) Are of an Unspecialized Type

34 Most and Least Radiosensitive Cells
Low Sensitivity Mature red blood cells Muscle cells Ganglion cells Mature connective tissues High Sensitivity Gastric mucosa Mucous membranes Esophageal epithelium Urinary bladder epithelium Very High Sensitivity Primitive blood cells Intestinal epithelium Spermatogonia Ovarian follicular cells Lymphocytes esOfogal spermAtogOnia

35 Acute Radiation Syndromes
Occurs if specific portions of body are exposed Not likely unless major organs involved 3 ARS syndromes: Hematopoietic (blood/bone marrow) rad Treatment: transfusions, antibiotics, bone marrow transplant Gastrointestinal (intestinal lining) rad Death likely if dose >1000 rad Treatment: make individual comfortable Central Nervous System (brain) 2000 rad or more Death likely within days H: Blood cells (most sensitive) G: GI cells (very sensitive) CNS: Brain and muscle cells (least sensitive) Sensitive organ: blood, intestinal lining, brain

36 LD50 for Humans Dose of radiation that would result in 50% mortality of in the exposed population within 30 days of exposure with NO medical treatment LD50 for Humans is 300 to 500 rad

37 Risks of Radiation Exposure
Low level (< 10,000 mrem) radiation Only health effect: cancer induction Average occupational dose to research and lab medicine personnel: <10 mrem/yr Amount is comparable to: 6 cigarettes/yr Driving 1,000 miles Living in a stone or brick home for 2 months Avg occ dose to RESEARCH AND LAB medicine personnel

38 Regulations / Guidelines
NRC Agreement States NCRP ICRP ALARA Program

39 Exposure Limits Regulations: NRC 10 CFR 20 Note old: New:
Whole body: 1.25 rem/quarter Skin: 7.5 rem/quarter Extremities rem/quarter New: Committed Dose Equivalent (CDE) Dose to a particular organ: Internal + External ≤ 50 rem

40 Exposure Limits Committed Effective Dose Equivalent (CEDE)
Dose to a particular organ or organs with weighting factor: Internal + External ≤ 5 rem Deep Dose Equivalent (DDE) Dose at a depth of ≥ 1 cm: Internal + External ≤ 5 rem (Eye ≤ 15 rem) Shallow Dose Equivalent (SDE) Dose to skin or extremity: External ≤ 50 rem

41 Exposure Limits Total Effective Dose Equivalent (TEDE)
Sum of dose from external and internal, including weighting: Internal + External ≤ 5 rem Effective Dose Equivalent Dose to organ or organs over one year period Total Organ Dose Equivalent Dose to organ from both internal and external: Internal + External ≤ 50 rem Exposure to Fetus (Declared Pregnancy) .5 Rem/9 months

42 Other Useful Information
6CE rule Efficiency = c/d, usually in percent Effective half life: Stay time = dose / dose rate REMEMBER UNITS!

43 Internal advisory body for ionizing radiation
Internal advisory body for ionizing radiation ICRP Publications (examples)  ICRP 84, Pregnancy and medical radiation  ICRP 85, Interventional radiology  ICRP 86, Accidents in radiotherapy  ICRP 87, CT dose management  ICRP 93, Digital radiology

44 National Council on Radiation Protection and Measurements
formulate and widely disseminate information, guidance and recommendations on radiation protection and measurements which represent the consensus of leading scientific thinking publication of NCRP materials can make an important contribution to the public interest. NCRP 148 – Radiation Protection in Veterinary Medicine NCRP 138 – Management of Terrorist Events Involving Radioactive Material* NCRP 134 – Operational Radiation Safety Training NCRP 120 – Dose Control at Nuclear Power Plants NCRP 115 – Risk Estimates for Radiation Protection

45 Control Programs for Sources of Radiation
Sealed Sources Radiation-Producing Machines Radioisotopes Radioactive Metals Criticality Plutonium

46 Control Programs for Sources of Radiation
Operational Factors Employee Exposure Potential External Hazards Internal Hazards Records

47 Common Radionuclides Sealed sources
Cs-137, Co-60, Ir-192, Am-241, Kr-85, Sr-90, Po-208 Liquid radioactive material for research P-32, P-33, S-35, H-3, C-14

48 Radiation Practice Problems Ionizing Radiation

49 Radiation Practice Problems
1. Iodine-131 has a radiological half life of 8 days. If a source originally contained 25 mCi how much remains after 18 days?

50 Radiation Practice Problems
2. Two measurements are taken on an unknown radiation source. The first was 1.3 mCi, and the second, taken 15 minutes later, was 0.05 mCi. What is the half life of this material?

51 Radiation Practice Problems
3. What is the exposure rate from a 15 Ci Cs-137 source at a distance of 1 foot? (Cs-137 gamma energy MeV) How about 10 feet?

52 Radiation Practice Problems
4. How long can a worker stay 10 feet away from a 15 Ci Cs-137 source without exceeding an administratively established quarterly dose limit of 1250 mrem?

53 Non-ionizing Radiation

54 What is Radiation? Radiation is energy transmitted by particles or electromagnetic waves Radiation can be ionizing or non-ionizing

55 Definition Non-Ionizing Radiation = Radiation that does not cause ionization Types of non-ionizing radiation include: 1. Ultraviolet (UV) light 2. Visible light 3. Infrared (IR) light 4. Microwaves 5. Radiowaves

56 Positive and negative charges cancel
Let’s Review – The Atom In their normal state, atoms are electrically neutral (no net charge) # protons = # electrons An atom that has gained or lost electrons is called an ion Positive and negative charges cancel

57 The Ionization Process
An in-coming photon interacts with an orbital electron The electron is ejected from the atom, and the atom gains a net positive charge. The photon generally transfers its energy to the electron and disappears. The in-coming photon must have enough energy to knock the electron out of its orbit. (The energy of the photon must be greater than the binding energy of the electron.) I think the minimum energy is about 10 eV…check me on that. Incident photon Ejected electron

58 Non-Ionizing Radiation
Non-ionizing radiation is electromagnetic in nature: This means it has characteristics of both waves and particles However, non-ionizing radiation behaves primarily as a wave Known as “wave-particle duality.”

59 Electromagnetic Spectrum
The electromagnetic spectrum covers an entire range of electromagnetic radiation Which of these are considered to be non-ionizing? Electromagnetic energy is present everywhere and exists over a VERY wide energy range. It extends over more than 25 orders of magnitude! Electromagnetic radiation is measured in terms of energy (eV), wavelength (meters), and frequency (Hz). The higher the energy, the higher the frequency and the shorter the wavelength (In other words, as the energy increases, the waves move faster and get closer together). Example: gamma rays have the shortest wavelength, so they also have the highest energy and frequency.

60 Electromagnetic Spectrum

61 Types of Non-Ionizing Radiation
Ultraviolet (UV) light Visible light Infrared (IR) light Microwaves Radiowaves

62 Non-Ionizing Radiation Terms
Wavelength Frequency Energy 10-18 m 3x1026 Hz 1.24x1012 eV 10-10 m 3x1018 Hz 1.24x104 eV 10-6 m 3x1014 Hz 1.24 eV 102 m 3x106 Hz 1.24x10-8 eV Terms Energy Frequency Wavelength

63 Ultraviolet (UV) Light
Ultraviolet light has a wavelength on the order of nanometers (nm) This is the shortest wavelength of all non-ionizing radiations 1 nanometer is 10-9 meters (very small!) Remember, shortest wavelength means it also has the highest frequency and highest energy of all non-ionizing radiations

64 Ultraviolet (UV) Light
Ultraviolet light cannot be seen by the human eye It is divided into 3 regions UVA (most energetic) UVB UVC (least energetic) UV light is divided into the regions based on energy and wavelength.

65 Sources of Ultraviolet Light
UV light is emitted naturally by the sun and stars It is produced artificially by electric lamps and light bulbs                             

66 Is Ultraviolet Light Dangerous?
All UV light can damage skin and eyes Over-exposure can lead to sunburn and various kinds of cancers, including melanomas It can also lead to weakening of the immune system UVA rays, which are not absorbed by the ozone layer, penetrate deep into the skin. UVB rays, which are partially absorbed by the ozone layer, mostly impact the surface of the skin and are the primary cause of sunburn.

67 Is Ultraviolet Light Dangerous?
UV damage to fibrous tissue is often described as “photoaging” Photoaging makes people look older because their skin looses its tightness and it wrinkles UVA rays contribute most heavily to premature aging. Up to 90 percent of all visible skin changes commonly attributed to aging are caused by sun exposure. However, it is interesting to note that an estimated 80 percent of a person’s sun exposure occurs before age 18.

68 UV Effects by Region UV-A (400-300 nm) UV-B (320-280 nm)
Pigmentation of skin or suntan UV-B ( nm) Erythemal region Sunburn of skin Absorbed by cornea of eye (welder’s flash) UV-C ( nm) Bacterial or germicidal effect

69 Protective Measures Ensure that skin and eyes are adequately protected (sunscreen, sunglasses, clothing) Never look directly at a source Operate UV lamps in light-tight conditions The earth’s atmosphere naturally filters out most of the UV radiation from space. The best way to use UV lamps is to ensure that they only operate in an enclosed space. Dark walls will absorb the light.

70 Visible Light The wavelength of visible light ranges from nanometers Visible light occupies the smallest segment of the electromagnetic spectrum

71 Visible Light Visible light is comprised of various colors
The separation of visible light into its different colors is known as dispersion

72 Visible Light Each color is characteristic of a different wavelength
The color “indigo” has been dropped Violet has the shortest wavelength (highest frequency) Red has the longest wavelength (lowest frequency)

73 Black vs. White Technically speaking, black and white are not colors at all Black is the absence of color White is the combination of all colors

74 Visible light health effects
Retinal burns Color vision Thermal skin burns

75 Infrared (IR) Light The wavelength of infrared light ranges from microns When an object is not quite hot enough to radiate visible light, it will emit most of its energy in the infrared 1 micron (1 micrometer) is 10-6 meters. This is one-millionth of a meter.

76 Sources of Infrared Light
Any object which has a temperature above absolute zero radiates in the infrared Even objects we think of as being very cold, such as an ice cube, emit infrared light The picture on the right is a thermal IR image of a person holding a burning match. The yellow-white areas are the warmest, and the purple areas are the coldest

77 Sources of Infrared Light
Even humans and animals emit infrared radiation Humans, at normal body temperature, radiate most strongly in the infrared at a wavelength of about 10 microns. The image to the right shows a cat in the infrared. Again, the yellow-white areas are the warmest, and the purple areas are the coldest.

78 Visible Light vs. Infrared Light
Some animals can “see” in the infrared These images give an idea of how different the world would look if we had infrared eyes For example, snakes can see in the infrared. Seeing in the infrared allows them to detect warm blooded animals. The image on the left is a visible view of Seattle. The image on the right is an infrared view of Seattle. If we could see in infrared, we would be able to see in the dark (you could see the person sitting next to you even if the room were completely dark) – infrared light – scroll down to “What is infrared?”

79 Is Infrared Light Dangerous?
Heating of tissues in the body is the principal effect of infrared radiation Excessive infrared radiation can result in heat stroke and other similar reactions, especially in elderly or very young individuals

80 IR Effects by Region IR-A (0.75 – 2.5 nm) IR-B (2.5 – 5 nm)
Penetrates skin to some extent Penetrate eyes to retina IR-B (2.5 – 5 nm) Almost completely absorbed by upper layers of skin & eyes IR-C (5-300 nm) Thermal burns on skin & cornea Cataracts (glass blowers)

81 Microwave Radiation The wavelength of microwave radiation ranges from about 10 microns to 1 meter Microwaves have very low energies and very long wavelengths

82 Microwave Radiation Microwave radiation has many uses, including:
Cellular phones Highway speed control Food preparation Microwaves interact most easily with objects of the same size, such as hot dogs or hamburgers.

83 Limit for Microwave Ovens
5 mW/cm2 at 5 cm from surface

84 Is Microwave Radiation Dangerous?
Exposure to very high intensity microwaves can result in heating of tissue and an increase in body temperature (thermal effects) At low levels of exposure, the evidence for production of harmful effects (non-thermal effects) is unclear and unproven The non-thermal effects seen in low level exposure studies have not been reproducible. Although the evidence is unclear and unproven, products such as cell phone “brain guards” have still begun to appear on the market.

85 Is Microwave Radiation Dangerous?
Currently, exposure limits are based on preventing only thermal effects Further research is needed in order to learn more about non-thermal effects

86 Radiofrequency (RF) Radiation
The wavelength of RF radiation (radiowaves) is greater than 1 meter That’s a long wavelength. Photons of radio and TV, whose wavelengths are measured in meters, interact with metal rods or wires called antennae.

87 Radiofrequency (RF) Radiation
Both microwaves and radiowaves are used in communication As a result, there is considerable overlap between what is identified as a radiowave and what is identified as a microwave

88 Is RF Radiation Dangerous?
As with infrared light and microwave radiation, the primary health effects of RF radiation are considered to be thermal RF radiation may penetrate the body and be absorbed in deep body organs without the skin effects, which can warn an individual of danger As with microwaves, more research is needed to understand non-thermal effects.

89 Static Magnetic Field Effects at Levels Below 0
Static Magnetic Field Effects at Levels Below 0.5 mT and Greater Than 0.5mT Nuclear Magnetic Resonance Imaging (NMR)

90 Static Magnetic Fields Introduction
Nuclear Magnetic Resonance Imaging Increasingly used in Biomedical Research in vivo analysis effectively displays soft tissue contrasts MRI is unobstructed by bone

91 Safety Concerns with Static Magnetic Fields
Attraction of Loose Ferromagnetic Materials Surgical Implants torqued, dislodged or rotated Pacemaker Interference Typically Seen Above 0.5 mT (5 Gauss)

92 SMF Exposure Limits / Guidelines
ICNIRP 200 mT Whole body (averaged for day) 5000 mT Limbs/extremities (ceiling) 40 mT Continuous general public exposure US FDA CDRH 4000 mT Routine Patient Ceiling ACGIH 60 mT {2000 T} Whole body (8hr-TWA) {Ceiling} 600 mT {5000 T} Limbs (8hr-TWA) {Ceiling} 0.5 mT Medical electronic devices

93 NMR Mapping 0.5 mT

94 Issues with Static Magnetic Fields < 0.5 mT:
Space constraints impacts all involved Concerns of stopping attention at levels below 0.5 mT Impacts finite radiation protection programs resources Facility Incompatibilities

95 SMF Affects Below 0.5 mT

96 SMF Problems Frequently Occurred
Screen “jitter” Other electronic interference Perceive Problem = Risk Dynamic Situation Can lead to other problems

97 SMF Recommendations Move “General Public” limit farther back
Move equipment to lower field levels Solicit worker concerns Map field strengths to near background levels Routine assessments encouraged

98 SMF Recommendations (cont.)
Area postings / brochures Educate workers about anticipated interferences

99 SMF Conclusion Be aware of potential equipment effects below 0.5 mT
Equipment incompatibilities may result in personnel management difficulties

100 A Quick Recap… 5 types of non-ionizing radiation include:
Ultraviolet (UV) light Visible light Infrared (IR) light Microwaves Radiowaves

101 What is a Laser? A device that produces light
LASER stands for Light Amplification by Stimulated Emission of Radiation

102 Laser Applications Consumer Products Laser Pointers Laser Printers
                                 Laser Pointers                    Laser Printers CD Players

103 Laser Applications                                  Medical- eye surgery, therapy for Carpel Tunnel Syndrome Industrial- welding, cutting

104 Light Basics Light travels in waves.
The electromagnetic spectrum is divided into sections based on wavelength.

105 What makes laser light different than conventional light?
Laser light has several unique qualities: Monochromatic Directional Coherent But what do these mean?

106 Monochromatic Light Monochromatic light is light consisting of one wavelength only. Monochromatic Polychromatic

107 Directional Light Directional light has very low divergence.
Conventional light spreads in all directions, but laser light remains focused. Directional Non-Directional

108 Coherent Light Coherent light consists of waves that are in phase with each other.

109 Lasing Material Lasers contain a medium which is used to cause the monochromatic effect. There are several states of lasing medium Solid State- Crystal injected “dopant” Semiconductor- Diode laser Liquid- dye laser Gas- C02 laser

110 Laser Construction Lasing Medium (gas, liquid, solid, semiconductor)
Excitation Mechanism (power supply, flash lamp, laser) Feedback Mechanism (mirrors) Output coupler (semi-transparent mirror)

111 Laser Construction (con’t)


113 Laser Use Research Medical/Dental Study of mechanisms at interfaces
Detection of single molecules Medical/Dental Eye surgery

114 Laser Use (con’t) Commercial Industrial Supermarket checkout scanners
Determining site boundaries for construction Industrial Cutting Welding

115 Laser Hazard Classification ANSI Z136.1-2000 Standard
Class 1 (Exempt) Incapable of producing damaging radiation levels Class 2 (Low power) Eye protection is an aversion response Visible ( nm) CW upper limit is 1mW

116 Laser Hazard Classification ANSI Z136.1-2000 Standard (con’t)
Class 3 (Medium Power) Divided into subclasses, 3a and 3b Hazardous under direct or specular reflection Non-hazardous under diffuse reflection Normally non fire hazard CW upper limit 0.5 W

117 Laser Hazard Classification ANSI Z136.1-2000 Standard (con’t)
Class 4 (High Power) Hazardous to eye and skin from direct viewing/contact, specular, and diffuse reflections Produce non-beam hazardous such as air contaminants Fire hazard

118 Bio-Effects Primary sites of damage Laser beam damage can be eyes skin
thermal (heat) acoustic photochemical

119 Eye Bio-Effects Three different ways for eye exposure
Retina (visible and IR-A) Cornea (UV-B, UV-C, IR-C) Lens (UV-A)

120 Eye Bio-Effects (con’t)
Visible ( nm) Possible damage to Retina

121 Eye Bio-Effects (con’t)
Near-ultraviolet ( nm) Possible damage to Cornea

122 Eye Bio-Effects (con’t)
IR ( nm) Possible damage to Lens

123 Skin Bio-Effects Skin Sensitivity Dermis (IR-A) Epidermis (UV-B, UV-C)

124 How Often Do Accidents Occur?

125 General Laser Safety Wear appropriate protective eyewear
Use minimum power/energy required for project Reduce laser output with shutters/attenuators, if possible Terminate laser beam with beam trap Use diffuse reflective screens, remote viewing systems, etc., during alignments, if possible Remove unnecessary objects from vicinity of laser Keep beam path away from eye level (sitting or standing)

126 Non-Beam Hazards Chemical Optical Fire Electrical
Chemical used in dye lasers can be known carcinogens or toxic also maybe difficult to dispose Optical Plasma radiation can be produced. Similar to welders flash Fire Class 3b and 4 lasers with high power outputs can cause fires Electrical Most common, very high incident in maintenance

127 Engineering Control Measures
Beam housings Activation Warning System Shutters Beam Stop or Attenuator Remote firing controls Interlocks Engineering controls are design features or devices that are applied to a laser or its environment for the purpose of reducing laser hazards. Engineering controls are considered to be the most effective types of control. Examples are: A list of required and recommended engineering control measures for each laser class is available in ANSI Z , Table 10

128 Administrative Control Measures
Class 3b and 4 Lasers Warning signs/labels SOPs Training Optical Paths Covered Warning Logo Information Label Class 2 and 3a Lasers

129 PPE Control Measures Gloves Be wary of neck ties. Special clothing Of particular importance in prevention of laser hazards is eyewear. Laser protective eyewear is usually made of filters which absorb and/or reflect specific wavelengths of laser light. An important factor to look for in choosing laser protective eyewear is the optical density (OD) of the lenses. The OD of the eyewear is a measure of its capacity to filter light; OD is the opposite of transmission. The higher the OD, the less the light that is transmitted to the eye. The OD must be chose so as not to impair vision significantly, yet at the same time, must be chosen so as to be capable of reducing the laser light to the MPE. When choosing laser protective eyewear it is also important to select eyewear that is designed to protect against the wavelengths of the laser light that will be used. Eye wear designed to filter shorter wavelengths of light are not appropriate for use with lasers that emit longer wavelengths of light. Laser protective eyewear cannot protect personnel if not worn. Eyewear must be for the appropriate laser wavelength, attenuate the beam to safe levels.

130 Emergency Procedure Shut down the laser system
Provide for the safety of the personnel, I.e. first aid, CPR, etc. If necessary, contact the fire department Inform the Radiation Safety Division Inform the Principal Investigator DO NOT RESUME USE OF THE LASER SYSTEM WITHOUT APPROVAL OF THE LASER SAFETY OFFFICER

131 Irradiance E = Irradiance = W/cm2 Ф = total radiation power W A = area
a = beam diameter r = viewing distance Θ = beam divergence

132 Beam diameter D = a + r Θ a = beam diameter r = viewing distance
Θ = beam divergence

133 Optical Density Log (incident power / transmitted power)
OD = log (total H / TLV)


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