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LSO-- Laser Safety Officer- a tutorial--


Well-known member
Apr 2, 2009
~40 more pages in the workbook




the max accessable emission level or collateral radiation within a particular class

Accessible radiation= lasers which humans can have access to.

Angular radiation= the apparent visual angle, a, as calc. from a soure that is accessaible to humans

Apeture+ the PJ opening - any radiation from there to which humans arte accessible

Apeture stop+ means an opening serving to limit the beam size. and thus the area exposed

******************Certified laser product= product is 'maker' certified to be compliant -- not all sellers who claim to be doing this are being truthful.

CDHR= Center for Devices and Radiological Health (of the FDA)

Classes of lasers= from Class 1 to Class 4- high number higher hazard and power

Collateral radiation= electronic product radiation (except laser) emmitted by a laser as a result of operation. again CFR 1040.10

Continous Wave or CW- Not pulsed

Cosmetic procedure protocol= delegated written authorization to select specific laser or IPL settings , initiate, -for procedures and conduct necessary follow-up.

Demonstration laser= any made, designed , intended, or used for purposs of demo-entertainment, advertizing display or artistic.

Embedded laser= enclodsed laser with higher class number than the inherent capibility --where the system's lower capability of the laser system in which it is incorperated.
(engineered features that limit accessible emission).

Enclosed laser= contained within its own protective housing or
laser made- designed, intended or used

'Federal performance standards for light-emitting products'
= the regulations in 21CRF 1040... incorp. by refernece, published by the Off. of Fed. Reg. Nat. Archives & records W D.C.

Human access= capasity to intercept laser or collatreal radiation by any part of the human body.

Incident= an event or occruance that results in actual or suspected exposure to laser radiation (light) that has caused or likely to cause damage.

Intergrated radiance= rad. energy per unit area of a radiating surface per unit solid angle of emission, expressed in joules per sq. cm. per steradian.

Irradiance = tme ave. radiant power incident on an element of a surface divided by the area of that element, expressed in watts per sq. cm.

Laser energy source= any device intended for use in conjunction with a laser to supply energy for the operation of the laser.
Gen. energy sources like mains or batts are not considered by the Agency

Laser facility.= place where one or more lasers are used. class of laser matched class of facility. highest prevails.

Laser product= any manufatured product or assembledge of componenets that constitutes, incorps., or intended to become a laser.

Laser protective device= any used to reduce or prevent exposure like eyeware-garments-engineering controls and op. controls.

Laser radiation= all electromag. rad. emitted by laser within range spect. range specified in def of laser-- result of controlled stim. emission or that is detectable eith radiation so produced through the appropiate apeture stop and within the approp. solid angle ofacceptance.

More definations; (paraphrased and (at times) crude abbreviations plus typos sry:eek:)

LSO- ..with combined experience (w/control & evaluation of laser hazards) & training any may be designated by the 'registrant' and has authority /responsibility to 'administer a program for a particular class of facility'.

Laser systems- = a laser with appropriate energy source w or w/o
additional incorperated components/

Limited exposure duration or Tmax= the exposure is limited by design or use.

Maintenance= self service intended by the maker- to ensure preformance. (more later on this)

MPE- (max permissible exposure)-the level where no harm or hazard.
for both eyes and skin as per ANSI Z136.12000.

Medical laser product- med device lasers- any body part and for purpose of diagosis, surgery, therapy, or relitive position of the human body. Like the red laser that used to aim the X-ray by some.

Operation= preformance of the laser product over the full range of its function. (But not maintenance or service.)

Protective housing= portians of laser product that are designed to prevent human access any radiation.

Pulse duraton = time increment measured between half-peak- power points.(at leading & trailing edges)

Pulse interval= period between identical points in two pulses.

Radiance= "time-averaged radiant power per unit area of a radiating surface per unit solid angle of emmission, expressed in watts per sq centimeter per steradian",

Radiant energy= energy emitted, transfered, or recieved in the form of radiation expressed in joules.

Radiant power= time-averaged power emitted , transferred, or recieved in the form of radiation expressed in watts.

RULE of the nines= when you hear of someone having 40% burns ..this is how they figure this using regions of the human body-
like head & neck 9%--

Safety interlock= system that prevents exposure by removing parts.
a protective housing .Not easily accessed.

Sampling interval= presented by the symbol "t" (in seconds) the time interval of sampling by measurement the radiation in the process.

Secured enclosure -area where causal access is impeded by various means like door locks, latch, or screws to secure.

Service= procedures or adjustments described in service manual

Uncertified laser product= laser NOT certified or meeting requirements -by 21CFR 1040.10 ( pretty much 95% (or more) of the PJs on Greedbay-

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Well-known member
Apr 2, 2009
TY Xman

I need to be ready for my do-over exam coming very soon.

so putting my notes etc here is good for me.

If people are going to do illegal shows at least they should learn enough to do a safe show- even if its for your friends at home--



Well-known member
Apr 2, 2009

The LSO needs to be familiar with many types ,wavelenghths , pulse shapes, modes, power and energy.

Common lasers
lasing medium----type--nm(common) --mode -- pwr/energy

Arg/K CW 454-457-476- TEM00 <30Watts
647-676( think B-G & R NOT LDs)


ND;YAG ND:YVO4 532 Multi-mode >6mJ per pulse

Copper Vapor Pulsed 578-510 Multi 1-2mJ per pulse
Laser Diosed (LD) CW 405-450-445 Multi >30Watts


Basic Radiometric units and measueement devices

Diff methods for type of laser-- also what measurements is being determinded.

ENERGY= (Rad E) the energy is the actual output of the laser, expressed on Joules(J)

POWER (Rad.Flux) PWR defined as energy per unit of time.
Example= 1Watt=1Joule for 1 second. Power is measured by a LPM.

IRRADIANCE Pwr on a surfgace , used to express the power density, defined as Watts per sq. m. or( W/m2)


Of these 2 concepts- Irrad. is most important for safety-

the absolute pwr does =not matter as much as how spread out the pwr is, when it enters the eye or falls on skin. a20W beam, spread out with a lens so it is 3 feet wide, may be perfectly safe to look at.

( BUT to be legal prior approval is needed on your variance. Conversely a 0.02 watt (2 mW) at close range and stared at, so all tyhe light enters the pupil, coul;d cause detectable changes in the retina.


MPE max permissible exposure

Laser calcs. rely ojn a concept called MPE-as the highest irradiance OR radiant exposure that is considered to be safe. It is expressed- in
W/cm2 or J/cm2.

there is no ONE number that is MPE- as that depends upon
object (eye or skin)

so its not a hard limit. going over a little will increase chance of damage but NOT certain..The MPE is set at 10% of the exp. that has a 50% probility of creating damage. or a that beam is 10 times the MPE
has a 50/50 chance of causing injury..

similair is AEL (acces. Emiss. Limit) its a product of MPE for worst-case acces emiss. and the area of the pupil of the dark adapted eye, which is taken to be *7 mm* for visible lasers.**
Thus the max light going thru 7mm NOT expressed in area (watts per sq cm)but simply watts.. ususally the AEL is seen in discussions of safety class limit--like class1 AEL is 1 mW.


time---- MPE (eye)
18usec -0.001 sec-----27mw/cm2
.001 -0.01 ---------10 mw/cm2
.01- 0.25 ----------5.6mW/cm2
.25- 1 sec-----------2.5mW/cm2
1 sec - 10 sec ----1.8mW/cm2

MPE for Skin

1 sec.exp--for vis and near IR= 1.1 W/cm2

even tho the skin is less effected all show need to be eye safe (NOT SKIN)

Even tho CDHR allows preformers to be exp. to class 2 (~2.5mW/cm2)
(if not required to view) its reccomended to limit to Class 1 for safety.

especially if ALL are not trained and aware of all risks.


Laser Haz. evaluations, range equations, & othher calcs.

the LSO is responsible for assessing any/all hazs with lasers. these CAN be performed based om=n manuf. info on lasers used. And the variance conditions under which the laser show is op. , actual measurements and clacs. of the laser. some useful haz. eval.eq. are NOHD ( Nominal Ocular Haz. Distance), O.D. of eye-ware. and soft pacakges on the market to aid the LSO w/ complex haz calcs. like
LaserSafe PC
Laserbee from Lucid Services LTD(UK)

indoor USA shows not aud. scan. have already (as part of the var.)
are done- no additional calcs. req. IF following all conditions of the var. .

OD of eyeware

that means
Optical Density- of the LSE (?laser safety eyeware or equip?)


be sure all three are correct-(found in laser manual)dont trust 100%)

Beam Diameter (a)

Beam Divergence (f)

Radiant Energy (Q) or radiant power (o with a vertical line)

they are in units of cm, radians,J and W respectively & in manuals.
however the central quantities in a laser safety calc. are the radiant exposure (H) (measaured in J/cm2)
AND the irradiance (E) ( measured in W/cm2) two values that are NOT common in the front of laser manuals.

There can be confusion on the profile of your beam..

& the choice of beam diameter common profile is a Gaussian profile.
The diameter (a) of a Gaussian beam be specified accordng to the 1/e oe 1/e2 point.
Laser makers may often use the 1/e2 definition since the area encompasses 90% of the total beam energy.
however , safety calcs use the 1/e diameter , so check which one you are using. ... the two diameters have a simple relation:



To calc for ocular or skin exposure you need nm-duration and size of source(whether its assumed to be a point source or not) When the 3 are known simly look up the MPE in reference tables. Working out the correct duration time depends on whether the exposure is intentional or accidental.

easy for intentional
but for accident one needs to know if a visible or non visible beam (IR)

for visible= it is asssumed that the blink reflex will protect the subject from exposure times longer than .25 sec.

for invisible+ a suitable durationtime is open to discussion. normally people do not stay still for very long and an exposure time of 10sec is a good compromise for oclur exposure and between 10 & 100 sec for skin.

MPE Table for visible CW at diff. exposure times

EXPOSURE ------------MPE for EYE

18usec-0.001 sec-------27mW/cm2

0.001 sec - 0.01 sec----10mW/cm2


That covers about half..

BBL with much more-

I have found MANY great links for LSO's ..these make the math much easier.
so you may want to place one or more on your desktop shortcuts or save as fav.

Some sites also have a quiz on laser safety- I will post some of those and we can look for the answers as they do not grade or give answers to these unless you register and send the completed quiz back.
I am also posting them at the show forum and those guys can help with getting her correct answers..

On-line free calcualtors are in several places- you just plug in the correct numbers---

IMO & AFAIK ... MPE is most important when the now hardly done 'Audience Scanning'-- so if a show has none of that there is no reall neeed to worry as the variance for both the projectors and the OP are covered in the variances. AND EVERY time you want to do audience scanning you MUST file a show plan and report-IF you do NOT audience scan your variance covers all you will do so you only need to keep a show plan on hand.

you must own very SPENDY LPM
AND take accurate readings from the closest place to the viewers-all this must be in your FDA report

Thus the reason for several pre show safety checks-- before each show-

the rest of the manual coming soon

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Well-known member
Nov 28, 2012
Greatly informative Len. Realize it takes a lot of time to do this. Can't REP you yet but the REP is insignificant compared to this information anyways.
Keep trying to reiterate to people just how strong those cheapo $4-5 pen lasers are but it seems like it's hard to get it through peoples heads. A 532nm 50mW cheapo pen will light a match easily when focused and the focused dot is EXTREMELY bright. See people over and over state they are familiar with the dangers and then in their next sentence show how ignorant they are. Just have to keep plugging away at safety.


Well-known member
Apr 2, 2009
well time to get back on track and finish this..

next month I will take the exam- so I need to finish the rest of the manual in this tut.
They tell us many questions will NOT be covered in the course as some knowledge is assumed to be learned elsewhere-in the field or by study- any search of 'laser safety' or LSO get more hits than you have time to read- any good links- practice exams etc PLEASE link them here.

- I see the need for trained LSO's incresing.
It would be a for sure a plus on your resume when looking for a job with a lasershow company. or on your own when dealing with LDs et al who have no clue about safe lasering.



Well-known member
May 14, 2011
well time to get back on track and finish this..

next month I will take the exam- so I need to finish the rest of the manual in this tut.
They tell us many questions will NOT be covered in the course as some knowledge is assumed to be learned elsewhere-in the field or by study- any search of 'laser safety' or LSO get more hits than you have time to read- any good links- practice exams etc PLEASE link them here.

- I see the need for trained LSO's incresing.
It would be a for sure a plus on your resume when looking for a job with a lasershow company. or on your own when dealing with LDs et al who have no clue about safe lasering.

Great series of posts---all good things for people who want to know what and LSO must know.

You should post or PM a link over the the Illinois guy who needs to become and LSO to own a class 3b or 4 laser. Here: http://laserpointerforums.com/f37/confused-about-illinois-law-93728.html


Well-known member
Apr 2, 2009
I did .. BUT the OP NEVER logged back in- but may have read our replies on a public computer not logged in.

Maybe a TROLL maybe he did not like our help--who kmows or cares..



time to finish the training manual and take the exam--

I now have a complete manual having been accidently shorted about 20 pages (another also got a short manual) and since we were allowed to use that during the exam I have been offered a free at-home exam( no $100 whew!)

Just to be clear- there and MANY 'kinds' of LSOs here we address ONLY entertainment lasers. AND even that being said---there is a ton more needed to have(mostly by exxperiece) to be a real competent LSO . Until you 'know-it-all' its a must to know where to find the help needed for any situation that comes up.. WE were offered by our instructor Greg Makov help via email when he can reply.
Some help can be gotten quickly at laser forums as well.

A search of 'LSO' gets a mountain of hits as EVERY school using laserds has safety concens and rules/regs etc-- some quizzes are there but some of the Qs are not what we know--PLUS you need to find the answers as they do not always give them...



Well-known member
Apr 2, 2009
Four Hazard Zones (HZs)
Nominal Ocular Haz. Distance
..its the distance from the apeture, along which the beam is an eye haz.--like if from 3k feet then from apeture to 3,000 feet away, the laser's irradiance exceeds the MPE.

For the math impared , like me. these simplified equations are still scary and the need of a scienticif calculator would be a must- as well as on-line help and software that does this- Its best to find the answer in more than one fashion with hope that the are both about the same answer- if not the LSO needs to make sure which is correct.. It takes years of in field experience to know just by looking what is safe or not.

the modern LSO is not actually required to do the math but does need to know how the numbers are derived.
One way is a pre-calculated table like the power/range table showing from 1 W to 40 W each of the four .

The NOHD mentioned above.

in this table all are CW & visible & 1mrad only
for other divergance you multiply the result by the increased mrad.
from the table:
40W w/ divergence of 7 .0
you divide by 7 the NOHD of 1 mrad

from table 40W @ 1 mrad = 4592 feet
/ by 7 = 656ft NOHD.
Clearly this manual needs to be handy on every occasion to be a LSO.

The tool a LSO needs is the soft that performs these instantly--


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Well-known member
Apr 2, 2009
Due to loss of ISP connection at any time I need to make this tut into short posts.
Haz. Analysis soft--
Skyzan from Rockwell looks like a great one.
Some offer 'light' version free or cheap BUT the full blown soft is NOT cheap nor are the fancy LPMs one should have.
___________________________________FAA and distances of safe use.

again NOHD the beam is an eye haz. (above MPE) from the source to thid distance.

The other 3 FAA dstances are similar. referring to distance =can cause visual interference with a pilot.
SZED (flashblindness)
Sensititive Zone Exposure distance
Critical Zone Exposure Distance (glare) beam is bright enough to block pilot's vision=
beyond this falls below 5 uW/cm2

'Laser Free Exposure Distance ( distraction) beyond this the beam falls below 50nW/cm2

to make this simple to LPFers here is the 5 mW 532 pointer.
NOHD is 52 feet
SZED is 262 feet
LFED is 11,712 (the beam can be a distraction up to 11,712 feet away!!

Beyond this laser beams should appear indistingushable from other lights.

The FAA calls the straight-line distance between the beam & object the 'slant range' just a fancy way of saying hazard zone.

For many this & other factors/reasons the FAA has made outdoor shows, just like audience scanning and mirror balls, sadly a thing of the past.
so the 5mW green is an eye hazard at 52 feet-- temp flash blind at 262 feet and Glare/disruption haz. at 1,171 feet.


Laser damage to tissue.
all 'kinds' are to be taken very seriously-- so safety will always be first and formost.

THERMAL EFFECTS: Any wavelength & a function of the irradiance or radiant exposure & the blood flow cooling potential of the tissue.

Photochemical efffects:from 400 to 550 nm or 'blue light'the effects are related to duration as well as repetition of the exposure as well also to the radiance or radiant exposure.

Acoustical transient effects: related to pulse duration & may cause & can occur in short pulses up to 1 ms. It is poorly understood can cause retinal damage not accounted for by thermal alone. Literally it 'pops' holes in the retina and many say they heard it happen.

Primarily laser exposure to the eye. Due to the focus of the eye potential injury is directly related to the wavelength of the laser. And its orders of magnitude greater than 'normal light'

Thermal burns:
also called lesions in the eye-& pretty horrific.. the choroid layer blood cannot regulate the heat loading of the retina. Followed by bleeding which can obscure vision well beyond the area damaged.

Some minor injuries heal while others result in temp. or perma loss of visual
acuitor blindness. And that is very bad --potential loss of ability to focus(read) and colorblindness can happen.

Photochem injury by UV exposure may result in photokeratoconjunctivitis (welders flash or snow blindness) Its very painful & may last several days & can be debilitating. Can cause cataracts when long term exposure.

How the eye is effected by different wavelengths..

The Cornea absorbs shorter than 400nm or longer than 1400nm.
The aquous humor, iris lens and vitreous humor absorbs 300 to 400 nm. those between 400 & 1400 are focused onto the retina.

severe injury can result due to local magnification (your eye's own lens). as low as just 1 mW/cm2 entering the eye- will be effectivly increased to 400 W/cm2.
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Well-known member
Apr 2, 2009
The length of exposure also effects eye injuries.
no injury would be expected by a visible wavelength (400 to 710nm) with beam power <1 mW &bstandard exposure of .25v sec (adversion response time) no injury expected from interbeam exposure. (classes 1, 2a and 2) .. but class 3a or higher for interbeam or specular reflection may cause injury before the .25 seconds is met. AND class 4 with 1ms pulse can cause substantial damage & bleeding & acoustic transient with substantial bleeding
if the MPE is exceeded the chances of an eye injury increase dramatically.



Two categories of skin injuries---thermal from acute exposure to high power and photochemically from cronic exposure by UV laser. And can range from minor to severe sunburn to skin cancer.

Skin burns are caused by any wavelength when the blood's cooling no longer keeps tissues cool. Results are a 'laser burn'.

Photochemical damage happens mostly in the blue-green range.
This can be seen as fuzzy vision when exposed to long durations of UV or blacklights.

Some meds may increase sensitivity. & again mostly with the blue-green lasers.


Well-known member
Apr 2, 2009
nearly done+++++++++

IMHO it just makes sense to completely avoid any lasers that expose the audience to laser radiation.

and there is this: No MPE for eyes or skin at ALL except specifically allowed by your FDA Variance.-quote from the class.

Non-laser hazards (likely more from these than the lasers) include the worst high voltage power.. so the LSO or his delegate must use all safety measures for these risks. Such as Cap systems -w/o safely done discharge. (Several times w/ mains off)and even then its a risk to not use qualified personel, plus, a working knowledge of CPR and keeping in mind at ALL times-it does not take super high voltage to kill-and its recommended that a 24 hrs stay at the hospital as on some occasions --- the worst happens even the next day and until that time most felt that they were OK..

The 'buddy system' needs to be used for this and many other tasks. OSHA makes a visit when the mandatory accident reports are filed..
The other chem. hazards involve flammable cleaning solvents.. adequate ventilation and storage needs attention of the LSO. Some of these cleaners have been linked with cancer.

Fire Hazard in Class 4.
any CW >500 mW can start a fire. ABC fireextingushers are required and must be up to date-fully charged etc. Bedam termination places must be fire proof. Like curtains-stops-barriers windowless brick or other fire proof material on buildings.

+++++++++++++++++ next we spent some time on the very strict 'rules' our poor friends in Arizona must obey while 'trying' to make a living with laser shows.

Lets just say they are VERY picky and have levied fines that IMHO are suspect. A full ten pages of codes w/o any pictures (lol)

Pretty sure its the most restrictive of any place anywhere ...

One fear I have is the laser 'pranks' (a misnomer if I ever saw one) may cause other states to go the way of Arizona- which DUH! will have no positive effect on the perps. BUT very bad for every one else.

IMO we should be reading twice as much advice about this issue as we do about safety glasses-- that is perhaps a vain attempt to protect one or a few --while NOT doing all we can to stop this. Positive peer pressure- its working on Bullies-- and doing our best to stop ALL lasers on people-aircraft animals, and vehicles goes right along with my refusal to label any laser 'eye safe'
as that is one of the most common excuses those arrested use- '5 mW! cant hurt a pilot' 'got it on EEKbay --must be legal'-- ' since the beam stopped I knew it was not reaching that far' etc
OK put away your books and get out a piece of paper QUIZ TIME!!!

I do have some more to add from my notes and other books etc-
So as you can see LSO is no simple occupation-great responsibilities.
I have requested a exam date-- I cannot provide you with the questions but there are many on-line laser safety quizzes. Some do not provide answers but you can look them up or send to the quiz provider for grading.

Any members with kiddos in school-- I hope you are asking them just what is being taught there about lasers in general and especially about safety and the aircraft thing.. it would be great if any member volunteered to speak to a class -show some basic lasers and answer their questions-but they must take away the fact that lasing at the wrong place and time must stop.

====if anyone has questions please post them here..


Well-known member
Apr 2, 2009
TY +rep
yes it took considerable time to write/copy all this. safety is too important to just skim the info.

anyone considering a career in laser shows needs to read.....


Well-known member
LPF Site Supporter
Jun 12, 2015
You’re welcome Len. :)
Has it been stickied yet, come to think of it? :thinking:
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Well-known member
Sep 10, 2014
Older post.. but great info... looks like I got some reading to do! Gotta hop out of hobby mode sometime