General Safety Awareness

Transcription

1

2 General Safety Awareness If you have not done so already, take the General Safety Awareness training Log onto access.caltech

3 Introduction LIGO Laser Safety Program LIGO-M v1 Based on ANSI Z136.1 American National Standard for Safe Use of Lasers

4 Introduction (cont) Topics covered: Why bother with laser safety? What is light? What is a laser? Point and extended sources Vision and skin» The eye» The retina» The skin Injuries Laser classifications Laser eye protection (LEP) Laser warning signs Terminology Responsibilities What to do in case of an incident?

5 Why bother with laser safety? Compared to natural light, laser light or laser radiation has some very special properties. These properties cover the nature of laser light and its biological risk factors. Most importantly

6

7 Why am I even here? I ve worked with lasers before. Why am I even here? What does this pie chart suggest to you?

8 Why am I even here? (cont.) Laser accidents by laser type Which ones do you think LIGO has?

9 Light (noun) What is light? The form of energy that makes it possible to see things: the brightness produced by the Sun, by fire, a lamp etc. (Merriam-Webster online dictionary)

10 What is light? Biblically (Genesis 1:3) And God said E. dd = q ε 0 B. dd = 0 E. dd = dφ B dd B. dd = μ 0 ε 0 dφ E dd + μ 0i and there was light.

11 The electromagnetic spectrum

12 What is a laser? Laser is an acronym for Light Amplification by Stimulated Emission of Radiation

13 Properties of laser light Monochromatic Low beam divergence Waves are in phase Polychromatic Highly divergent Waves have random phase

14 Biological effects of laser radiation The nature and site of the injury depend on the following: Wavelength» Determines what part is exposed Output power Exposure duration» Calculations done at 0.25 s for visible light, 10 s for infrared wavelengths, or the appropriate exposure duration (eg. 8 hours)

15 The eye

16 How do I see? Retina has two types of photoreceptors Rods Cones Rods are more sensitive Cones provide colour sensitivity Concentrated in the macula

17 Image formation by the eye Light is focussed by both the lens and cornea Focal length, f eye ~ 17 mm Pupil diameter, d ~ 7 mm

18 Point and extended sources

19 Point and extended sources (cont) Pretty much all lasers can be treated as point sources Irradiated spot on the retina can be as small as 7 20 µm in diameter 5 mw (legal laser pointer) 13 kw.cm -2

20 Optical gain of Wavelengths between nm focus onto the retina The retinal hazard region The smallest pupil diameter is 2.2 mm The smallest resolvable spot on the retina is 7 µm in diameter The ratio of the two is approximately

21 Absorption of radiation by the eye

22 Wavelengths in LIGO

23 Spectral response of the eye Peaks in green Just because you don t see it, doesn t mean it s not hazardous

24 What is wrong with this picture?

25 Visual acuity A measure of how good your vision is Snellen test Dutch opthalmologist Herman Snellen ( )

26 An optical illusion

27 Aversion response When exposed to bright, or intense, light a person s natural reaction is to blink and move their head out of the way Aversion response 0.25 seconds

28 The skin UVC dangerous rays UVB burning rays UVA tanning rays Strong absorption in the infrared

29 A small compendium of laser related injuries INJURIES

30 Retinal injury example #1 Laser light show at a dance club 510 nm, 2 mw laser Corrected visual acuity was 20/800 Patient recovered after surgery Remember 2 mw is generally considered safe! Image credit: Clin Ophthalmol 2014: 8:

31 Retinal injury example #5 Accidental exposure to a Q-switched Nd:YAG laser without laser eye protection Experienced a bright flash, followed by sudden loss of vision No recovery of visual acuity after 6 years Image credit: Korean J Ophthalmol 2009 Sep; 23(3)

32 Retinal injury example #6 532 nm, 150 mw laser pointer Immediate blurred vision Waited two weeks before seeking medical attention Visual acuity was 20/32 in right eye, 20/25 in left eye after treatment Image credit: N Engl J Med 2010; 363;

33 Retinal injury example #7 Exposure to 200 ps stretched pulses Peak intensity > W.cm -2, average power a few watts Laser eye protection was worn Intense blue light, loud sounds of pops and a crackling noise, dark cloud in vision

34 Sclera injury example #1 Combined CO 2 /Nd:YAG laser W CO 2 laser 7 8 W Nd:YAG laser Visual acuity was 20/125, 5 days after treatment Recovered after 7 months Image credit: Arch Ophthalmol 2000; 118(6)

35 Skin injury example #1 CO 2 laser burn study conducted over 20 years 5 W.cm -2, 1 s pulse Other than scarring, no detrimental effects

36 Possible eye injury symptoms Headache after exposure Seeing flashing lights, especially in the dark Shadows in your peripheral vision Excessive watering of the eyes Sudden appearance of floaters An audible pop at time of exposure Difficulty detecting the colours blue or green Vision going cloudy at time of exposure or shortly thereafter Burning pain

37 Possible skin injury symptoms A sensation of warmth resulting from the skin s absorption of laser energy 0.1 W.cm -2 produced a sensation of warmth UVA ( nm) Skin discolouration or darkening Reddening of the skin (erythema) UVB ( nm) and UVC ( nm) Blistering Reddening of the skin

38 LASER CLASSIFICATIONS AND LASER EYE PROTECTION

39 Laser classifications The higher the class, the greater the potential hazard Class 1, Class 1M Class 2, Class 2M» Visible light only, output less than 1 mw Class 3R All classes listed above present little or no eye hazard Within LIGO we are mainly concerned with Class 3B and Class 4 lasers

40 Class 3B, Class 4 comparison Class 3B Class 4 Can be visible or invisible Output between mw Direct or intra beam exposure Hazard from Can be visible of invisible Output greater than 500 mw Direct or intra beam exposure Specular reflection Specular reflection Eye hazard Diffuse reflection Eye hazard Skin hazard Combustion hazard

41 Terminology Maximum Permissible Exposure (MPE) The level of laser radiation to which an unprotected person may be exposed to without adverse biological effects to the eye or skin. Nominal Hazard Zone (NHZ) The space within which the level of direct, reflected or scattered radiation may exceed the MPE. At the observatories, the entire LVEA is an NHZ.

42 Terminology (cont) Standard Operating Procedure (SOP) Formal written description of the safety and administrative procedures to be followed in performing a specific task. Laser Safety Officer (LSO) One who has responsibility and authority to monitor and enforce the control of laser hazards» At LHO, Peter King» At LLO, Danny Sellers» At Caltech, Eric Gustafson» At MIT, Peter Fritschel

43 How do we protect ourselves? Awareness through training Control measures Engineering» Laser enclosures» Beam enclosures» Access control Administrative» Following procedures (SOPs)» Warning signs» Communication to and with others Personal protective equipment Laser eye protection

44 Optical density What is optical density? OD = log 10 transmittance Alternatively OD = log 10 1 transmittance

45 Optical density (cont) Optical density Transmission 0 100% +1 10% +2 1% %

46 Laser eye protection The purpose of laser eye protection (LEP) is to attenuate any laser radiation that might strike it to a safe level Types of LEP Absorptive Reflective Combination of absorptive and reflective LEP should (preferably) conform with ANSI Z87.1 Should be marked with Z87+ somewhere

47 Appropriate choice of LEP Advocated as being suitable by a former staff member

48 Choosing the right LEP You be the judge.

49 Examples of LEP Absorptive polycarbonate Typically green or orange coloured Relatively light

50 Examples of LEP (cont) Absorptive glass Typically have a grey/bluish tinge Heavy

51 Examples of LEP (cont) Absorption coated glass Grey/bluish tinge with a coating

52 Examples of LEP (cont) Reflection coated polycarbonate

53 Examples of LEP (cont) Combination absorptive glass and reflection coating

54 Prescription LEP Prescription LEP is available Unfortunately not many frame styles to choose from Use an prescription insert

55 Prescription LEP (cont.) Please do NOT do this do it yourself laser eye protection!

56 Anti-fog insert LEP accessories Eyeglass holder

57 Identification of LEP What to look for? Structural integrity of the frames Scratches, cracks and pits in the lenses OD and wavelength region markings

58 EN 207 LEP Markings are somewhat more complicated Rated by: Working mode Wavelength range Scale numbers (similar to OD) Pulse length

59 A precautionary tale Always check the condition of the LEP 300 mw through a good region 4.3 W through damaged region

60 A precautionary tale (cont.)

61 Does LEP work?

62 Trade-offs in selecting LEP Visible light transmission Ideally as high as possible Comfort Weight Fit Prescription eyewear Coated LEP is only good for a small range of acceptance angles (~ 30 )

63 What is wrong with this picture?

64 Old signs Laser warning signs

65 New signs Laser warning signs

66 Signal words Danger Imminently hazardous situation which, if not avoided will result in death or injury Warning Potentially hazardous situation which, if not avoided, could result in death or serious injury Caution Potentially hazardous situation which, if not avoided, may result in minor or moderate injury

67 Matching eyewear to the laser use area This set of eyewear is marked: nm OD nm

68 Responsibilities As a person with basic laser safety training you are allowed to Do what you are told to do As a person with basic laser safety training you are NOT allowed to: Operate a laser by yourself Make unsupervised changes to the beam path by yourself

69 sometext Responsibilities

70 What to do in case of an incident? What do I do if I think I was hit by a laser? Notify those in the immediate area and switch off the laser Remove yourself from the hazard zone Seek medical attention as necessary Notify your supervisor or the LSO as soon as possible

71 Other hazards Remember that more can hurt you than just the laser Electricity Pressure Chemicals Mechanical hazards Confined space Cryogenics Laser generated airborne contaminants Housekeeping Fatigue Your co-workers!

72 Summary Working safely around lasers is possible Respect all warning signs Always wear your laser eye protection If you have questions, please ask the LSO

73 What is wrong with this picture?