Talk:Laser safety

What is safe?

There seems to be considerable disagreement on reasonable safety guidelines. The initial version of this article seemed to justify (or try to justify) practices which include systematic breaching of laser safety regulations. In particular, it was considered safe to routinely work without safety glasses, even when dealing with class-IV lasers, provided that some guidelines are followed. Surely such practices would be allowed by safety regulations if it could be convincingly shown that they are safe. However, for many reasons (some of which are now given in the modified article), they are not safe. A former colleague of mine worked exactly in this style (no glasses, but keep out of the experimental plane) with a 500-mW Nd:YAG laser. He was later told by a doctor that peripheral regions of both his retinas are burned. He had not noticed that, but with somewhat less luck it could have hit the central portion of the retina, blinding him for ever. He then changed his style; at earlier times, I had been unable to convince him to use his glasses.

Even though most laser operators have probably at least sometimes breached some safety regulations, there is an important difference between occassionally breaching a rule oneself and publicly recommending such breaches to others as allegedly reasonable practices. The latter can hardly be considered responsible. Therefore, I strongly recommend not to return to a relaxed version before laser safety experts can be convinced to include such practices into official rules and guidelines.

RPaschotta 13:38, 30 Oct 2004 (UTC)

---

I think that after your edit, the article is reasonably NPOV, discussing both common practice and objections against it. (As opposed to earlier versions that could be read as promoting dangerous behaviour and then as moralizing).

By the way, I think most operators are actually more careful with class 4 lasers. I haven't found a table that lists the exact tresholds for the different classes at various wavelengths, but the treshold for class 4 seems to be around 500 mW. Diffuse reflections from pieces of paper with 500 mW visible light are definitely unpleasant to have within your field of view -- and likely harmful as well, so people tend to be more careful with those.

More philosophically, one could wonder where one should put the boundary between acceptable and unacceptable risks. The chance of dying from head injury is about the same for an hour of car driving as for an hour of cycling (quite low compared to other risks in either case). However, few find it reasonable to recommend helmets to car drivers. Laser accidents happen, but are not very common, and I have not heard about anyone who actually completely lost sight in an eye. The worst I know of is someone who damaged 30% of the central view area of one eye due to a reflection from a mixing crystal.

Han-Kwang (talk) 15:54, 30 Oct 2004 (UTC)

It appears to me that the recommendations made in 2004 have not been implemented. The text still appears to condone unsafe behavior. Eyewear must be worn when engineering or other controls are inadequate to eliminate the potential exposure in excess of the applicable MPE. There have been dramatic improvements in eyewear coatings in the past few years. Eyewear can now be tailored to block only the harmful wavelengths produced by a given laser. The eyewear is also lightweight and comfortable, so the old excuses no longer apply. In the US, your employer is mandated by law to provide you with the safety equipment mandated by the ANSI Z136.1-2000 standard. In the case of Class 4 lasers, this applies to the purchase of eyewear, signage, viewing aids and laser access control systems.

1sciguy 18:25, 6 April 2007 (UTC)

It's an open encyclopedia: go ahead and edit it. However, if you update it, make sure that it's NPOV - something that already lacks now. The article is really not supposed to tell the reader what to do and what not to do - but rather explain what are common practices and what official regulations are. Han-Kwang 19:23, 6 April 2007 (UTC)

disputed

It says most laser pointers are class II. Where's the evidence for this? They're class IIIa or IIIb. Class II lasers have minimal output intensity, like that from an LED. Also see my counterclaims at Talk:Laser. lysdexia 21:25, 21 Dec 2004 (UTC)

Laser proof curtain is necessary

Blink reflex does not work when you look at sun behind a curtain. It also applies when we exposed to a laser behind a curtain however, it is still dangerous it will burn points where the picture of light holes focus in the retina. All fabric curtains have these direct holes. --Mahdig 31 October 2006 (UTC)

I'm not sure what you mean. Of course, a laser curtain should be made of a material that doesn't transmit any light, but not for the reason you mention. The images of the holes on your retina are too low in intensity to cause harm (For the record, I regularly hold pieces of tissue paper into multi-watt beams and watch them without any harmful effects). However, typically part of the beam will propagate into the same direction after going through the tissue or open fabric. If your eye is in that beam path, it will of course be very unhealthy, since that beam will be focused onto a single spot on the retina. Han-Kwang 23:59, 31 October 2006 (UTC)

You said, "The images of the holes on your retina are too low in intensity to cause harm". It will be true only when the harm of light is thermal. However, in visible light region, the harm of laser to retina is photochemical and the size of picture in retina does not change harm effect. about the test you have done that I think you mean that when you look at a lamp behind a tissue the flash blindness does not occur however it occurs but in the points with distance to each other so it is not so noticeable. The problem exists with ordinary plastic curtain, too. Because you can see bright light behind them that it means that, it has holes. --Mahdig 14:06, 1 November 2006 (UTC)

I still have no clue what you are talking about. I see that you created an article Cutains and The blinking reflex containing the above comment. I strongly suggest that you add a diagram, remove the two spelling errors in the article, and add some context. As the new article is now it is non-encyclopedic and a very likely candidate for WP:AFD. Also please remember WP:NOR. Han-Kwang 14:42, 1 November 2006 (UTC)

May be you understand what I am saying if you use a cloth instead of a tissue (tissue holes is very small) and with dark color and put it in front of your eye when looking to a lamp. Mahdig 18:52, 26 November 2006 (UTC)

OK, you mean that a laser-shielding curtain should be absolutely light-tight. Agreed. But that doesn't have anything to do with the blinking reflex. Han-Kwang 19:36, 26 November 2006 (UTC)

Assenment scale

I'd say that this article definately needs an A-class or at least a GA-class rating on the assesment scale. I have nominated it for one of these ratings. G man yo 09:55, 28 February 2007 (UTC)

What do these classes mean? Pzavon 15:24, 28 February 2007 (UTC)

Reasons for GA Failure

Unfortunately I have failed this article as there are a few areas in which I would like to bring to attention to the editors of this article in order to hepefully bring it up to standaeds in the future.

1. The name of the article (Laser safety) is not mentioned in the introduction and not emboldened as mentioned in WP:MOS
2. Secondly, there are very few interwikis is the second half of the article, therefore once again it is not up to the standards of WP:MOS.
3. The different classes for the old system and the revised system should be in subcategories instead of just emboldened as mentioned in WP:MOS.
4. There are only 2 categories, I'm sure they could be a few more added.

If this article was improved in the ways mentioned above and any other areas in which editors bring to attention then it may pass in future months/weeks.Tellyaddict 13:00, 3 March 2007 (UTC)

Leakage of high-power IR pump beam from DPSS laser pointers?

Anything authoritative on this issue?

• [1] (scroll down to "Yet Another caution note on DPSS laser pointers")
• [2] "It's also possible for a misaligned green pointer to let out IR while still throwing a green beam; that can happen if you drop them and their internal alignment goes bad."

"(From The Physical and Theoretical Chemistry Laboratory Oxford University)"

Which makes the whole section a copyvio... ed g2s • talk 13:30, 9 August 2007 (UTC)

I'll try to rewrite the section one of these days. Han-Kwang 10:04, 10 August 2007 (UTC)

Excellent in general, but lacking some necessary details

The Class 1 and Class I limits are clearly stated in the abstract ==> laser exposure may not exceed the MPE. However, while Class 2 and Class II limits are correctly expressed the for *visible* light (which Class 2 and II are specific to) Class 3x and Class IIIx and higher classifications continue to assume visible light. For instance, I work with lasers which regularly emit powers greater than 10 mW but which are still Class 1 - according to this page they would only possibly be Class 3b and Class IIIb due to the clear statement for each that lasers emitting greater than 5 mW radiation are such. There is also a serious problem with an earlier statement (section titled Classification) that the relevant units for MPE are W or J, and switch to W/m^2 at wavelengths greater than 4 um. This is just wrong. The relevant units are always, specifically, radiant exposure (in J/cm^2) or irradiance (in W/cm^2) for both MPE evaluation and classification. Statements like, "output may not exceed 5 mW" are rules of thumb for point-source lasers (in this case for visible Class IIIa lasers) which have implicit assumptions about beam diameter, ocular aperture, aversion response time, etc. built in. Looking first for response. If I have time perhaps I'll try to improve this. 64.32.245.242mjd 2007-10-29 16:42 EDT

You don't indicate where you are located and which jurisdiction's laser safety regulations you are working with. On the issue of whether a 10mW laser could be Class 1, I believe the US FDA/CDRH regulations are structured so that such a laser could not be Class 1. Pzavon 02:16, 30 October 2007 (UTC)

According to IEC60825-1, the accessible emission limits (AEL) for class 1 are 0.39 mW for visible light (-700 nm), 10 mW for 1400-4000 nm, and 1 kW/m2 above 4000 nm. In the range 700-1400 nm, there is a wavelength dependence. However, the wavelength and pulse duration dependence is -not surprisingly- just as complicated as for the MPE plots, and I don't think it is very meaningful to specify it in so much detail. In principle, classifying a laser and sticking the correct warning labels on a laser is the duty of a manufacturer, who surely has a copy of the regulations. The user of the laser just has to read the label "class 1" and understand that it is safe to use without eye protection, or "class 3B" and understand that it is dangerous. The article just gives a few example AEL values for common types of lasers. I will clarify that a bit, although it is for example clearly mentioned that the 5 mW limit for Class 3R is for visible, continuous lasers. I don't have access to the old classification (the IIIa description in the article does not mention the wavelength range.) Pzavon, do you have a copy of the US and/or old regulations? Are the MPE/AEL numbers the same as in the IEC standard (I have the 2007 revision)? Han-Kwang (t) 15:42, 30 October 2007 (UTC)

Harm through eyelids

I removed this: **When picking up something from the floor, closing the eye may not give sufficient protection against multi-watt laser beams, as the eye's lid is partially transparent, particularly for infrared light. Closing both eyes when kneeling becomes second nature and automatic for workers in such fields.. Not only is the remark about the second nature a bit strange, but also the first part is not correct. Although the eyelid may not absorb near-IR light, it still scatters the laser light which prevents the light from being focused onto the retina. Of course, a 10 W beam with a 3 mm diameter will probably burn the eyelid and possibly damage the cornea underneath as well, but this is not a very likely situation in a research lab, where the smell of burning clothes, skin, and wall painting would have drawn attention before. Han-Kwang (t) 22:24, 1 November 2007 (UTC)

Burning sweater in my case. ;) --Chuck Sirloin 17:15, 2 November 2007 (UTC)

Suggestion for additional reference

I suggest to insert the following additional reference, which is a page of my own "Encyclopedia of Laser Physics and Technology": article on laser safety in the Encyclopedia of Laser Physics and Technology

RPaschotta 16:34, 5 Nov 2007 (UTC)

Edits on class 4 and treatment lasers

Regarding these edits, I think I agree with Pzavon, both on how a class 4 laser can damage skin and on the suitability of therapy lasers for this article (i.e., not suitable). Therapy laser treatment seems to be an interesting topic though, that would probably be suitable for an article of its own with a bit more background on what kind of medical conditions this laser treatment would deal with. Han-Kwang (t) 00:46, 16 December 2007 (UTC)

Old/new classification

I think the sections on the old and new classifications should be merged. Most of the specifications overlap. I think there should be a small intro about the differences between the schemes, and then Class 1/I can be discussed together. IN the current version there's too much duplicate info. Han-Kwang (t) 18:01, 12 February 2008 (UTC)

I disagree. The systems are distinct and separate in that the old system has regulatory force in the US and not elsewhere. The "new" system is a revision developed primarily in the EU and being adopted elsewhere, including the US. The purpose of two sections is to make it clear and easy to see the range of each system and to recognize the differences. In the US, symbols and phrases from both can be encountered at the same facility. Even the use of Arabic vs Roman numerals is easier to show clearly with a separate listing. And the new classes (1M, 2M, and 3R) do not have a precise one-to-one relationship with the replaced classes (IIA and IIIB). Perhaps some text can be combined, but the Hazard Class numbers should be displayed as two separate sequences. Pzavon (talk) 03:28, 13 February 2008 (UTC)

I will think about how to combine some text. The problem is that I am not familiar with the details of the old system to really be able to give an overview of the philosophies behind the two systems.

Something else: your recent edit summary: The definition of Class 4 is based upon determinations of what will damage skin. I looked it up, thinking that it was "skin damage OR dangerous diffuse reflectios", but indeed, The IEC standard says about class 4: "...for which intrabeam viewing and skin exposure is hazardous and for which the viewing of diffuse reflections may be hazardous. (emphasis added) Apparently, also from the description of class 3B, a laser can be dangerous in diffuse reflections without causing skin damage, and vice versa. I'll clarify this. Han-Kwang (t) 13:05, 13 February 2008 (UTC)

Your assessment of the basic criteria for Classes 3B and 4 is correct. Pzavon (talk) 03:21, 14 February 2008 (UTC)

Problem with Class 2 Caution label text provided at line 90

This illustration of a label claims that eye damage could result if a Class 2 beam is directed at the eye for more than 10 seconds. such a label seems "off" to me. I am not aware of any labels containing explicit time limits. Can anyone really familiar with practice in the EU say whether such a label is actually in wide use? Pzavon (talk) 23:42, 16 March 2008 (UTC)

Laser pointer safety

I have edited the laser pointer section to reflect that, although red laser pointers appear to be safe and this shouldn't be denied, the overall tone of the article should still emphasise laser safety and the dangers of lasers in general. The paragraph removed consisted solely of an implication that people who complained over laser pointer exposure were liars, fraudsters or crybabies, which isn't too value adding above a simple statement of the fact that damage is unlikely to occur.217.154.66.11 (talk) 19:41, 14 April 2008 (UTC)

In research enviroments

I just rewrote the section about conventional practice in research labs because I felt it was too much POV-, essay- and howto-like. Unfortunately, this is a subject that everybody who works in this area seems to know, but nobody writes down, probably because of legal consequences, so it still looks a bit like original research. I know many people who have had laser-related eye injury in a lab. The worst case is someone who damaged 30% of one fovea, meaning he can't use that eye for reading. And then there are many people who have a small burn. I did once have the opportunity to visit the R&D department in a laser factory, and the procedures were pretty similar to what I've seen in many university labs (goggles are available but only worn during very specific high-risk procedures). Any suggestions for references? Han-Kwang (t) 18:07, 6 July 2008 (UTC)