Laser safety - please read!!!!!!!!!

As many people already know, lasers are divided into classes based on their output power and therefore their potential danger.

Oddly enough, there seems to be a lot of people who disagree with these classifications and their danger levels, so hopefully this thread clears things up a bit.

Let me start by clearing up a common question:

Q: DO I NEED GOGGLES TO PROTECT MY EYES FROM DAMAGE CAUSED BY MY LASER?

A: If the laser produces more than 4.95mW of output, YES YOU NEED GOGGLES!!!! The usage environment is irrelevant. If the laser produces more than 4.95mW, then you need to use goggles. ANY LASER OVER 4.95mW REQUIRES GOGGLES TO PROTECT YOUR EYES.

Wikipedia describes the laser classes in detail here:
Laser safety - Wikipedia, the free encyclopedia

The following was copied from the above Wikipedia page:

Laser Classifications

http://en.wikipedia.org/wiki/File:Laser-symbol.svgBelow, the main characteristics and requirements for the classification system as specified by the IEC 60825-1 standard [3] are listed, along with typical required warning labels. Additionally, classes 2 and higher must have the triangular warning label shown here and other labels are required in specific cases indicating laser emission, laser apertures, skin hazards, and invisible wavelengths.

Class 1

A class 1 laser is safe under all conditions of normal use. This means the maximum permissible exposure (MPE) cannot be exceeded. This class includes high-power lasers within an enclosure that prevents exposure to the radiation and that cannot be opened without shutting down the laser. For example, a continuous laser at 600 nm can emit up to 0.39 mW, but for shorter wavelengths, the maximum emission is lower because of the potential of those wavelengths to generate photochemical damage. The maximum emission is also related to the pulse duration in the case of pulsed lasers and the degree of spatial coherence.

Class 1M[/COLOR]

A Class 1M laser is safe for all conditions of use except when passed through magnifying optics such as microscopes and telescopes. Class 1M lasers produce large-diameter beams, or beams that are divergent. The MPE for a Class 1M laser cannot normally be exceeded unless focusing or imaging optics are used to narrow the beam. If the beam is refocused, the hazard of Class 1M lasers may be increased and the product class may be changed. A laser can be classified as Class 1M if the total output power is below class 3B but the power that can pass through the pupil of the eye is within Class 1.

Class 2

A Class 2 laser is safe because the blink reflex will limit the exposure to no more than 0.25 seconds. It only applies to visible-light lasers (400–700 nm). Class-2 lasers are limited to 1 mW continuous wave, or more if the emission time is less than 0.25 seconds or if the light is not spatially coherent. Intentional suppression of the blink reflex could lead to eye injury. Many laser pointers are class 2.

Class 2M[/COLOR]

A Class 2M laser is safe because of the blink reflex if not viewed through optical instruments. As with class 1M, this applies to laser beams with a large diameter or large divergence, for which the amount of light passing through the pupil cannot exceed the limits for class 2.

Class 3R

A Class 3R laser is considered safe if handled carefully, with restricted beam viewing. With a class 3R laser, the MPE can be exceeded, but with a low risk of injury. Visible continuous lasers in Class 3R are limited to 5 mW. For other wavelengths and for pulsed lasers, other limits apply.

Class 3B

A Class 3B laser is hazardous if the eye is exposed directly, but diffuse reflections such as from paper or other matte surfaces are not harmful. Continuous lasers in the wavelength range from 315 nm to far infrared are limited to 0.5 W. For pulsed lasers between 400 and 700 nm, the limit is 30 mJ. Other limits apply to other wavelengths and to ultrashort pulsed lasers. Protective eyewear is typically required where direct viewing of a class 3B laser beam may occur. Class-3B lasers must be equipped with a key switch and a safety interlock.


[With class 3b, the diffuse and/or matte reflections might be harmful if the power is high enough and the eye is in close proximity to the reflection. Simply put, keep your distance from diffuse reflections from high-powered (150mW +) class 3b lasers, and keep the time that you view them to a minimum. Or just use goggles]

Class 4


Class 4 lasers include all lasers with beam power greater than class 3B. By definition, a class-4 laser can burn the skin, in addition to potentially devastating and permanent eye damage as a result of direct or diffuse beam viewing. These lasers may ignite combustible materials, and thus may represent a fire risk. Class 4 lasers must be equipped with a key switch and a safety interlock. Most entertainment, industrial, scientific, military, and medical lasers are in this category.


There are many variables involved in calculating safe exposure under a specific set of circumstances (beam path, reflections, divergence, power, pulse rate [if applicable] etc, etc,) so really it's just best to treat all lasers above 4.95mW of output power with the same respect as one would treat a weapon. If the laser produces more than 4.95mW, it is dangerous and safety precautions MUST be observed.


YOU ONLY GET ONE SET OF EYES. They're not replaceable. If you injure one permanently, it will affect you for the rest of your life. DON'T TAKE UNNECESSARY CHANCES.


AND IF YOU ABSOLUTELY MUST TAKE UNNECESSARY CHANCES, DON'T COME HERE AND TALK ABOUT IT LIKE IT'S OK. IT'S NOT OK!!!!


IF YOU WANT TO BLIND YOURSELF, NO ONE HERE CAN STOP YOU, JUST DON'T POST HERE ABOUT HOW YOU "SHINED YOUR BLU-RAY LASER INTO YOUR EYE AND NOTHING HAPPENED, SO IT MUST BE SAFE". THOSE KINDS OF POSTS PUT OTHERS AT RISK.


Important additional reading: http://www.army.mil/usapa/med/DR_pubs/dr_a/pdf/tbmed524.pdf


More to come later...

FYI, might want to change the font colour, it's kind of hard to read the main body of text on the standard background.

Info looks good in there - only suggestion I have is a very quick summary paragraph or table, since many people will just float over the actual text (sad, but that's what the internet has become).

"A Class 3B laser is hazardous if the eye is exposed directly, but diffuse reflections such as from paper or other matte surfaces are not harmful."

I have quoted this part several times when telling people about laser safety, but I always make sure to include warning about prolonged exposure and distance from the diffuse reflection.
I think it is very important to include this information here as well. Otherwise we might have people burning paper 6 inches from their face with a 450mW laser and expecting it to be all fine and dandy.

Seb

Hopefully the color's better..

Still got a couple of leftover [ color ] tags in there

Hope this gets stickied - awesome post, should be required reading for all new members.
:topic:

I'll find it, you guys compile it.

Then we and others will review it.

Lets rip the solar example and some pictures out of this one:

http://euverc.colostate.edu/safetytests/laser_safety_manual.pdf

Also has a nice way of calculating goggle OD from power

Coherent has a video:

Coherent Inc. : Laser Safety

This guy has good tips.

Koch Labrotocols/Laser Safety - OpenWetWare

# Use a safer laser, if possible. That is, if you don't need invisible laser, use a visible one. If you only need 1 mW and your laser is 100 mW, consider affixing a neutral density filter to the laser to make it generally safer.
# Spend the money on the required safety materials. An obvious one is laser safety goggles of the correct and comfortable type. Less obvious are things like a camera able to detect IR light, to make wearing safety goggles less annoying.
# Always think about your eyes, your lab-mates' eyes, and visitors eyes.
# Consider what happens when other people mess with what you're doing. E.g., what happens if 20 8th graders come into the room? If you're the only one who can reasonably use the laser, keep the key on your keychain.

* In addition to laziness and a cavalier attitude, the laser accident at Los Alamos is attributable to a lack of imagination about who may be using the laser (i.e. a person shorter than 5' 10" or whatever).

# Don't wear shiny things below your elbows. Rings, watches, etc. These can specularly reflect laser light into someone's eyes.
# Try to keep the laser beam parallel to the floor and far below eye level (this is a problem when people are sitting in the room). If you need to increase the height of the path, do it so the beam is vertical. You're avoiding situations where you're aligning a beam that would be at eye level if you miss your target.
# Isolate laser operations from people not involved in the operation. I.e. with a black curtain, or a special dedicated laser room.
# Use interlocks to automatically shutoff the laser when rare situations happen. E.g., you can connect the door to a room to a laser interlock.
# Explain to others who enter the work area why they are safe, and how to stay safe. If it's just a plain safe laser (e.g. 1 mW red laser), don't assume they know that.
# Enforce safety on others and kick their ass if they won't be safe.

More good stuff, although the 15 mW number is a bit high, change that to class IIIA for beginners :

http://www.ehs.uci.edu/programs/radiation/Standard Operating Procedures for Laser Safety.pdf


ILDA's site, a bit wimpy on morals, but hey...

Laser Pointer Safety - Tips on keeping laser pointers safe and legal


This is start, I will find more over the following days, and scan stuff in, that I have.

A bit bizzare, but good tips on goggles...

http://www.eyesafety.4ursafety.com/laser-eye-safety.html


Steve

Thanks for putting this together EF.

I wanted to be sure that these two document got linked in the post as well. They are the ones that Steve posted in the earlier thread, they are a good read.

http://www.army.mil/usapa/med/DR_pubs/dr_a/pdf/tbmed524.pdf

http://www.laserfx.com/BasicSafety/Chapter 5 Quantifying the Laser Radiation Hazard.pdf

My favorite guide made by laservision. Explains the EN-207 standard, in my opinion a very usefull standard, better than ANSI Z136.

I really hope no one in canada is so much of a dumbshit that he/she will shine it at an airplane or something and get it banned.


EDIT: the reason i say this is because in a Wikipedia link above it says that canada was thinkin of gettin rules on lasers. Hope no one does any thing stupid so we get rules like other countrys