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Laser pointer safety basics

This is really all you need to know:
  1. Don't shine a laser of any power level on anyone at any time. 
  2. Normal Lasers up to 5mw represent no harm whatsoever to anyone or anything anywhere (but see the next point).
  3. Some green lasers emit harmful levels of infrared light (IR). Don't take a chance by looking down the barrel of a laser - period - on or off, Especially if it is on but does not appear to be emitting visible light. It could be emitting dangerous levels of IR which can cause even more damage to your eye (See "Invisible dangers" below). 
  4. Power levels above 50mw represent increasing levels of danger.
  5. 80mw lasers can cause damage that takes time to heal.
  6. Permanent optical damage can occur very quickly at levels of 100mw and greater.
  7. Blindness can occur instantly at levels above 300mw
  8. Don't shine any laser on an automobile in motion or aircraft in flight - It's a federal crime and you can go to jail (see "Legal issues" below).
  9. Shine it at a cop could get you shot.
If you want to know more, continue on...

20 July 2017 Update:

Very little on this page has changed in the six years since I created it. It's still the "Wild-wild-West" when it comes to the purchase and quality of lasers. One thing that HAS changed significantly are the availability of lasers with power ratings above 500mw. Another thing that has changed are the number of suppliers, mostly on Ebay and off-shore E-commerce sites. It's even more caveat emptor than it was in 2010. For what it's worth, the two documents at the next two links provide the latest FDA takes on lasers for our use.

There are some differences between these documents and what I wrote in 2011 but they are inconsequential for our needs in the Astronomical community so I did not make any other changes here. Other changes since 2011 include the number and variety of suppliers of all sorts of laser powers AND colors. Included in this increase are the availability of lasers with powers above 500mw as mentioned. When I wrote this page in 2011, a 1000mw (1 WATT) green laser could only be found only in a large box suitable only for desk and laboratory work - not portable to an astronomical site by any means. Today, a handheld 1 watt green laser can be had for as low as $79.99 (and I aint sayin where). So as Sgt. Esterhaus used to say "Let's be careful out there".

2] As of April 2017: Laser Products and Instruments 

Readily available hand held green lasers, prices and hazards: 

 Power level



 up to 5mw

 Less than $40


 30mw to 100mw

 $40 to $150

 Moderate - Can cause damage that requires time to heal

 101mw to 250mw

 $250 and up

Can cause permanent spot damage in moments.

 251mw to 500mw

 $500 and up

 Will cause permanent spot damage instantly

 500mw and higher

 $999 and up 

 Will cause permanent blindness instantly (cooks eye lens)


Visible dangers
The highest powered hand held Green laser pointer I've found so far is 700mw at $1400.00
So far, cost has limited the availability of lasers above 150mw at Star parties. Apparently there is a new technology that promises to get higher powers at lower costs so we will be dealing with these and higher powered lasers in the near future.
1-3 watt Green lasers are large desktop models > $5000.00. We won't see them at star parties in the near future but if we do, we need to shut them down immediately.
Here’s a link to a desktop green laser burning through cardboard. Note the smoke begins almost immediately:
With regard to the actual optical damage caused by lasers:
I am finding anecdotal references and am continuing the search for hard research. What appears to be the consensus for laser pointers between 80 and 250mw is that the damage to the eye occurs in the form of spot damage. In the case of the lower power range, small areas of the eye are immediately damaged due to burns as opposed to instant, irreversible damage.
These damaged areas appear as blind spots much like that found in the fovea. You don't notice them until you start looking for them. As the power level increases, the severity of the damage increases.
Laser powers above 300mw appear to cause almost instantaneous and noticeable damage. Again the severity is power based.  Most of the references of this nature come from the ophthalmology field and requires translation into layman’s terms.
Lasers above 500mw can cause instant blindness as the power level literally cooks the lens of your eye as it severely burns the retna.

Invisible dangers
The light from a green laser starts off as a very high intensity Infrared beam. Partway through the emission processes, this IR light is converted to Green light.
Infrared light can cause significantly more damage to your eye than the same level of visible light. The reason is because your reflexes almost instantly cause you to look away and close your eyes in the presence of a very intense beam of light. This automatically limits the amount of damage that could be done to your eye.
Since you can't see IR, you can't react to it like visible light. This allows the full intensity of the beam to cook your retina and/or lens until you figure out what's going on. Unfortunately, once you realize you are losing your eyesight, it's too late.
Most lasers have a filter to prevent leakage of any remaining IR content. Note the word MOST. This filter can be left out or even removed by the manufacturer or individual making modifications to standard lasers.
Don't take chances - Don't look directly into a laser even if you think it's dead.

Legal issues
As to the legal aspects, it’s pretty much the Wild West. There are a number of federal import regulations but it’s pretty much on the honor system and does not cover possession limitations. State and local regulations are more oriented towards Laser shows.
There are federal laws making it illegal to shine a laser at aircraft in flight. This is one of those "Ten years and/or $10,000 fine" kinds of things. Its a felony so you lose your rights upon conviction.
Many states have laws making it a felony to shine a laser into a moving vehicle. Again, you'll lose your rights on conviction.
Since cops are well aware of laser aiming devices on firearms, shining a laser at a cop could get you shot.
Act responsibly and courteously by not shining the laser at anyone or anything.

Laser Classes:
Here is an excerpt from the Center for Devices and Radiological Health (CDRH) regulation 21 CFR 1040.10 and 21 CFR 1040.11, the standard classification for lasers with some additional comments by Wes Ellison (erl@sunflower.com):
Class I laser products
No known biological hazard (Comment from GM: unless the laser is removed from the enclosure. Then the usual power warnings apply). The light is shielded from any possible viewing by a person and the laser system is interlocked to prevent the laser from being on when exposed. (large laser printers such as the DEC LPS-40 had a 10 mW HeNe laser driving it which is a Class IIIb laser, but the printer is interlocked so as to prevent any contact with the exposed laser beam, hence the device produces no known biological hazard, even though the actual laser is Class IIIb. This would also apply to CD/DVD/Blu-ray players and recorders (which might have Class IIIb laser diodes of 100 mW or more) and small laser, as they are Class I devices).
Class II laser products
Power up to 1 milliwatt. These lasers are not considered an optically dangerous device as the eye reflex will prevent any ocular damage. (I.e., when the eye is hit with a bright light, the eye lid will automatically blink or the person will turn their head so as to remove the bright light. This is called the reflex action or time. Class II lasers won't cause eye damage in this time period. Still, one wouldn't want to look at it for an extended period of time.) Caution labels (yellow) should be placed on the laser equipment. No known skin exposure hazard exist and no fire hazard exist.
Class IIIa laser products
Power output between 1 milliwatt and 5 milliwatt. These lasers can produce spot blindness under the right conditions and other possible eye injuries. Products that have a Class IIIa laser should have a laser emission indicator to tell when the laser is in operation. They should also have a Danger label and output aperture label attached to the laser and/or equipment. A key operated power switch SHOULD be used to prevent unauthorized use. No known skin hazard of fire hazard exist.
Class IIIb laser products
Power output from 5 milliwatts to 500 milliwatts. These lasers are considered a definite eye hazard, particularly at the higher power levels, which WILL cause eye damage. These lasers MUST have a key switch to prevent unauthorized use, a laser emission indicator, a 3 to 5 second time delay after power is applied to allow the operator to move away from the beam path, and a mechanical shutter to turn the beam off during use. Skin may be burned at the higher levels of power output as well as the flash point of some materials which could catch fire. (I have seen 250 mW argon set a piece of red paper on fire in less than 2 seconds exposure time!)  A red DANGER label and aperture label MUST be affixed to the laser.
Class IV laser products
Power output >500 milliwatts. These CAN and WILL cause eye damage. The Class IV range CAN and WILL cause materials to burn on contact as well as skin and clothing to burn. These laser systems MUST have:
A key lockout switch to prevent unauthorized use Inter-locks to prevent the system from being used with the protective covers off, emission indicators to show that the laser is in use, mechanical shutters to block the beam, and red DANGER labels and aperture labels affixed to the laser.
The reflected beam should be considered as dangerous as the primary beam. (Again, I have seen a 1,000 watt CO2 laser blast a hole through a piece of steel, so forget your eye, imagine what it would do to your head!)
References (local files)
I have uploaded several files that I found very useful in this research. Here are the files and a short description (click on the name to view the file):

ASEM SLAS Laser Presentation.pdf:

PDF of power point presentation at both SLAS and ASEM meetings. General overview of current (2010) state of the art of green lasers and issues.
Web page image with nice overview and citations
Good overview of available models and operation.
Very detailed and comprehensive document covering laser safety for the lay person and hobbyists. Focuses on lasers used for astronomy.
Title: A Green Laser Pointer Hazard
NIST technical paper (easily understood) covering the following
  • The basic operation of a green laser pointer
  • Harmful Infrared emission hazard
  • Description of a simple "CD" based test and test setup to detect IR emissions from regular hand held green laser pointers..
Extract from OSHA manual regarding how OSHA treats laser hazards. This is the contents of the document:
I. Introduction
II. Nonbeam Laser Hazards
III. Biological Effects of the Laser Beam
IV. Laser Hazard Classifications
V. Investigational Guidelines
VI. Control Measures and Safety Programs
VII. Bibliography
Appendix III:6-1. FDA-CDRH Requirements for Laser Products
Appendix III:6-2. FDA-CDRH Federal Laser Product Performance Standard Evaluation Outline
Appendix III:6-3. The American National Standards Institute (ANSI)
Appendix III:6-4. Warning Signs
Appendix III:6-5. Glossary of Laser Terms 
A highly technical paper conducted for the US Air Force research laboratory. Contains a vast amount of research results with regard to human eye operation and sensitivity to various amounts and types of IR and visible radiation. 

Report of live tests conducted on individual with cancer propr to removal of the eye. These tests were conducted using a 5mw green laser on a patient who fixated the gaze for periods of 1 minute to 15 minutes. 

Web based References and Links as of Jan 2011 
(As always, these links can go stale so my apologies ahead of time)
The best first order reference is Wikipedia:
And here’s another good web site that covers the Laser spectrum:
This subsection on safety and the ramifications of various power levels is particularly good:
OSHAs’ perspective: These are probably the best I've found after a few hours of research
Air force research laboratory
Grant Martin,
Jan 31, 2011, 12:06 AM
Grant Martin,
Jan 31, 2011, 12:07 AM
Grant Martin,
Jan 31, 2011, 12:32 AM
Grant Martin,
Jan 31, 2011, 12:09 AM
Grant Martin,
Jan 31, 2011, 12:07 AM
Grant Martin,
Jan 31, 2011, 12:08 AM
Grant Martin,
Jan 31, 2011, 12:07 AM
Grant Martin,
Jan 31, 2011, 12:08 AM