What would make for the most useful light in thick smoke?

I would like to gather ideas about how to create a light that would cut through thick smoke and give an edge to any fireman lucky enough to have one. My uncle is a volunteer firefighter, and he was showing me his 'smoke cutter', which is a 4xAA light with a standard incandescent bulb and an amber LED. The amber LED is what he was excited about, because with only that LED lit he was able to see much better in smoky areas than with other lights. Of course, right away I thought, "There must be a way to make a better one...".

I have been thinking about a multiple LED light, but I suspect that one could have too much light in this application, kind of like using high beams in a blizzard. And a wider spectrum of color seems like it would aid in depth perception and could penetrate even better if it was of a longer wavelength. Shorter wavelengths like green or blue scatter in smoke and restrict vision. A red-orange LED (or two or three ) would provide a lot of visible light that meets these criteria. So, besides knowing how many LEDs is too much, there must also be some ratio of amber to red-orange LEDs that would be the most effective. Perhaps someone has suggestions or knowledge of this sort of thing?

Sorry if this belongs in General Flashlight Discussion, I'm not sure which is most appropriate.

I'm thinking there's no "too many" LEDs, but the tighter the beam the better. With less spill there is less backscatter.

Cyan coloured lights are sold on the basis that they perform well in fog/smoke. I do not own one but a search in this area may give some useful info.

I was hoping to have more of a floodlight on the basis that it would be used primarily indoors in situations where awareness of your surroundings is of paramount importance. But if spill causes a backscatter problem then perhaps there is a good reason why a light like this is not in use. :shrug:

After reading through this thread I found following Hodsta's advice, I think flood is bad for shorter wavelengths that scatter in fog and smoke, but may be OK for long wavelengths. Posts 10 and 14 are particularly relevant. My uncle's 'smoke cutter' had no optic or reflector for the amber 5mm LED, and he said it worked great. That means it probably has a 15 degree beam at the low side with lots of spill.

The most effective way to use such a light is to hold it as far away from your body as possible. (Not that you will be able to see anything in thick smoke.)
Much of the loss of vision is because of the light reflecting back from the particles in front of you.
The best way to do that in a fire is to hold it as near the ground as possible since there will be a bit less smoke down there.

But even in a wildland situation, in broad daylight, in thick smoke you can't see past the front of your googles.

Any professional/volunteer firemen out here to give their professional experience?

Karl

Mike Painter said:

The most effective way to use such a light is to hold it as far away from your body as possible. (Not that you will be able to see anything in thick smoke.)
Much of the loss of vision is because of the light reflecting back from the particles in front of you.
The best way to do that in a fire is to hold it as near the ground as possible since there will be a bit less smoke down there.

But even in a wildland situation, in broad daylight, in thick smoke you can't see past the front of your googles.

Click to expand...

A telescoping body could assist in holding a light away from your body.

Welch Allyn patent description

Kohler LightHawk light sent for Utah miners vs. dust Here it is shown at BrightGuy's site. ? Hype or real fog/smoke/dust benefit ?

I would say that you are going in the right direction.

I would also add that a set of 'optics' worn by the rescuer might also aid in their vision in such conditions.

In particular, I am thinking of the eyewear (shades) with the brand name Ambervision. (I believe these are sometimes sold in local Walgreen's)

I have noticed that these glasses help not only with sunlight, but during rain, or foggy weather. They cut right through the haze and glare that are normally encountered.

I also know it sounds crazy... but... try it.

Regards,

James Jackson

smoke and fog are kinda different things, IMO anyway, but you ever notice on a lot of cars with true fog lights that they are amber? I too am toying with the idea of making some lights for the FD as both my brothers are there, one paid and the other a volunteer. I really want to make a couple lights and hand them off to folks on the next big house burn they do. could be really fun. Just wish they would let me mooch a suit and go in, but they wont as I am not a volunteer :mecry:.

This line added because a reply can't be entirely a quote.

There is no good reason why fog lights are yellow. Here is an
excellent explanation provided by Professor Craig Bohren of Penn State
University:


"First I'll give you the wrong explanation, which you can find here and
there. It goes something like this. As everyone knows, scattering (by
anything!) is always greater at the shortwavelength end of the visible
spectrum than at the longwavelength end. Lord Rayleigh showed this, didn't
he? Thus to obtain the greatest penentration of light through fog, you
should use the longest wavelength possible. Red is obviously unsuitable
because it is used for stop lights. So you compromise and use yellow
instead.


This explanation is flawed for more than one reason. Fog droplets are, on
average, smaller than cloud droplets, but they still are huge compared with
the wavelengths of visible light. Thus scattering of such light by fog is
essentially wavelength independent. Unfortunately, many people learn
(without caveats) Rayleigh's scattering law and then assume that it applies
to everything. They did not learn that this law is limited to scatterers
small compared with the wavelength and at wavelengths far from strong
absorption.


The second flaw is that in order to get yellow light in the first place you
need a filter. Note that yellow fog lights were in use when the only
available headlights were incandescent lamps. If you place a filter over a
white headlight, you get less transmitted light, and there goes your
increased penetration down the drain.


There are two possible explanations for yellow fog lights. One is that the
first designers of such lights were mislead because they did not understand
the limitations of Rayleigh's scattering law and did not know the size
distribution of fog droplets. The other explanation is that someone deemed
it desirable to make fog lights yellow as a way of signalling to other
drivers that visibility is poor and thus caution is in order.


Designers of headlights have known for a long time that there is no magic
color that gives great penetration. I have an article from the Journal of
Scientific Instruments published in October 1938 (Vol. XV, pp. 317-322).
The article is by J. H. Nelson and is entitled "Optics of headlights". The
penultimate section in this paper is on "fog lamps". Nelson notes that
"there is almost complete agreement among designers of fog lamps, and this
agreement is in most cases extended to the colour of the light to be used.
Although there are still many lamps on the road using yellow light, it
seems to be becoming recognized that there is no filter, which, when placed
in front of a lamp, will improve the penetration power of that lamp."


This was written 61 years ago. Its author uses a few words ("seem",
"becoming recognized") indicating that perhaps at one time lamp designers
thought that yellow lights had greater penetrating power. And it may be
that because of this the first fog lamps were yellow. Once the practice of
making such lamps yellow began it just continued because of custom."


Also, take a look at the following web site:
http://www.gi.alaska.edu/ScienceForum/ASF5/593.html

Dr. Lawrence D. Woolf
General Atomics

Click to expand...

I remembered seeing this offering from Lumaray while back it designed for fog
http://www.lumaray.com/home_800.html. I wonder how well it would work?
Craig (LED museum) and Quickbeam have reviewed their products favorably, and their a CPF sticked dealer. maybe Craig will pop up and review this.

Some of the recent posts have made it clear to me that there is a substantial difference between the scattering properties of fog and smoke. So while fog may not be subject to Rayleigh's scattering law, smoke is comprised of much smaller particles and should be considered independently.

This abstract states that the most prevalent particle size in wood smoke is 0.1 to 0.2 microns. This puts the particles near the range of the shortest wavelengths of visible light (violet @ 400 nanometers=0.4 microns). Rayleigh scattering is only a major effect if the particles are smaller than the wavelength in question. So, even though the 0.1 to 0.2 micron particles are not major contributors to scattering, smoke also contains even smaller particles that would scatter to a greater degree. Rayleigh scattering occurs when x<<1 for x=2*pi*r/lambda where r=particle radius and lambda=wavelength of light. Also, the intensity of scattered light varies inversely with the fourth power of the wavelength, so shifting the wavelength has a big impact on the degree of scattering. Therefore, I think Rayleigh's scattering law should apply to smoke even if it does not apply to fog (which it evidently does not), and it is quite possible that a white LED comprised mostly of blue wavelengths could scatter heavily while a longer wavelength such as amber would not.

I am thinking of a maglite with 27mm reflectors and either 3 or 4 LEDs. I think amber should outnumber red-orange LEDs when building with an odd number. They could be 3 Watt Luxeons to give a lot of light. With Vf of about 3 volts per emitter and much more forgiving V vs. I curves for amber and red-orange luxeons, I could probably get away with direct drive from a 9.6V pack for 3 LEDs and a 12 to 13.2V pack for 4 LEDs.

I just wanted to chime in to say that 3 or 4 IMS 27mm reflectors will not fit in a C/D mag. You have to use atleast 20mm reflectors. Due to the small size of the reflectors you can use, your high power Luxeon III R/O and Amber may give you poor results. The die on the Luxeon III R/O is so large, that you get a pretty large moon shaped beam even when mated with a 27mm reflector. Things get worse when using the 20mm or even 17mm reflectors. A Lux I, a Lux K2, or even the Luxeon Rebel versions of the Amber and R/O have about the same sized die (and are much smaller in comparison to the LuxIII die). Sure these do not "handle" 1500mA, according to the specs sheets, but I am sure you can overdrive them to 1000mA, or you may be able to get away with 1500mA if you can just manage the heat. The K2 may perform the best since the package is more durable than the Luxeon I. The Rebel is another story. I have some R/O 0050 Rebels in front of me now (never powered them up yet), and I think that it is completely viable to use them.

You would have to buy different samples of each and experiment with different reflector combos. What if you got one of those cheap Chinese flashlights that have a really big head for hundreds of 5mm LEDs and mod it so it can fit 3 or 4 IMS 27mm reflectors easily. I seen it done before. I was tempted to do the same.

If scatter is a such a big deal, then why would you want a broad beam with a bright corona that you may get with the small reflectors like the IMS 20mm and 17mm? Is unwanted, excessive spill and corona any more important than enough lux? Why bother with the multi reflector approach when you can use one Amber or R/O emitter with the stock reflector. You may not have as many lumens, but dang you will have a very tight focused beam with little spill and barely any corona. You can even use the Luxeon III emitters since you have such a big reflector. You will get good battery life this way and you will only have one overdriven LED to heat sink on a beautiful O-Sink. Just a thought. I have a modified Cree P4 (without a dome and retaining ring) set in a 3C Mag that is slightly overdriven and it is focused so well that I have a super tight, and very bright spot that will out-throw every other light I have (including a ProPoly modded with a Seoul P4).

I have a quad white 2D Mag, and damn it is bright and it has a decently small hot spot, however, it has such a massive corona that using this thing in fog or light smoke (when neighbors are burning stuff) is horrible. Talk about not seeing your target very well... I wish that the beam was more throwy, but I had to deal with the fact that I am using IMS 20mm reflectors. Maybe, someday, I can upgrade to McR-20 reflectors.

Why is white LEDs so dang horrible if there are many firefighters using flashlights with super-tight spots like the Streamlight ProPoly 4AA and 3C, and the Streamlight Survivor? I am not a fireman either, but I know a few volunteer firefighters and I see one of them love their Survivor. I have seen it, and even though it uses the 'ol Luxeon III, the thing is very bright and it is nothing but throw! The reflector is ridiculous, as it is so wide and so deep. I want to get one of those and mod it with a better LED. It has to work atleast somewhat if it is sold to firefighters as a firefighting tool. If brightness is an issue, then one can modify them with the latest in high efficiency emitters. I have a thread where I modified the ProPoly 4AA to use the Seoul emitter. It is so much brighter, but I do not know if it is any better suited to be used for firefighting because the corona is a bit brighter. This is due to the way the Seoul P4 is made, though. It can be modded with the Luxeon Rebel 0100 or a Cree Q5 (with the lens and ring removed), and you will have a super bright hotspot without that bright corona that can scatter back. These white LEDs behind a big mag reflector may work even better! You can even throw an Amber or R/O emitter behind the big, deep reflector of one of those three mentioned Streamlight flashlights if you really desire the color.

What do you think? I am not trying to shoot down any of your ideas, I am just trying some ideas of my own. Those Streamlights must have been tested extensively in smoky rooms and environments before they were ever considered to be sold to firefighters. I am not just singling Streamlight, either. Other brands using big and deep reflectors would work equally as well.

-Tony

I certainly agree that corona and spill are counterproductive in smoke when using white LEDs. The question in my mind is if the same is true for amber or red-orange. If so, then your idea of using just one amber LED in a mag would make the most sense. Otherwise, I think the spill could serve to add peripheral awareness in a dangerous situation where it is highly desirable. It seems that real world experiments are in order...

from my experience, playing with RGB, with smoke fog and water (in a creek), just stay away from the blue. for some reason it causes more visable backsplash to the human eye when it hits the surface of the particals.
and the "amber" glasses, and amber lighting people mention is real life examples of such. (amber = -blue)

toss the math and science, build a fire ok a BBQ.

it should not be how well the light is seen in the smoke,
not how much light makes it past the smoke,
not how much light the smoke lights up,
but how well a human (with a adjustable iris) can see another human, THROUGH the smoke using the light. the answer is not in the smoke, but on the other side of it. its contrast and perception, not light meters.
green (not cyan because of the blue) leds are very bright, so testing with green and red to make the yellow/amber might be interesting. also fire is already kinda yellow/amber, so the green might be helpfull in offsetting that. an amber light aproaches a fire person, they might douse you
also water would exist in a situation like that too, with a mist wall in front of you penetration of the fog/water might be nessisary.

"white" leds, which are blue dies with yellow phospors, light up smoke and fog like crasy, making it great for beam shots and all, that is probably why the fireperson, avoids them. also the incandescent filiment is some 1200* already, a led doesnt like being heated.

mudman says:
It seems that real world experiments are in order...
and in the real world is where it will be used.

If you think a single-emitter amber light would do the trick, then you might want have a look at MSaxatilus' sale of his amber (D4F) Milky-modded Surefire L1:
https://www.candlepowerforums.com/threads/172405

Interesting discussion. Color of light and intensity make a difference. flood vs thrower may make a difference in smoke.

I shot two beam shots tonignt during a dust storm. the first a 64625 13.2v pak and HD set 12.8V. second 64430 substitute Tungsram 56580 35w, 6v pushed to 9.63v at the pins = over 70w and looks to punch through.

https://www.candlepowerforums.com/threads/172505

afraidofdark said:

If you think a single-emitter amber light would do the trick, then you might want have a look at MSaxatilus' sale of his amber (D4F) Milky-modded Surefire L1:
https://www.candlepowerforums.com/threads/172405

Click to expand...

Thats a floodmaster reflector and you'd get too much backscatter.
Have you seen Pelican Recoil LED lights?
You could swap out the white LED for an amber. Its all beam and no sidespill and made for cutting through smoke. Not powerful enough to go thru dense smoke but an idea to build on perhaps.

Working through college I sold public safety equipment, 30+ years ago. A product made then by Optronics was a sealed beam spot that had a mask on the face to block certain portions of the reflected light. The filament was covered with a half sphere mirror so no light went foward, it all was reflected back to the reflector. The center of the face was masked and so were the edges in an elliptical pattern. The beam did penetrate better than an unmasked bulb of this type. The mask was opaque and colored blue for the consumer (that had no bearing on the optics) and it was called the "blue eye." Apparently this was a focused beam with the stattered side spill removed.