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Do BLUE lights cut through smoke better?
Has anyone heard about BLUE LED helmet lights?
The local FF shop has them in stock on the theory (from the salesman) that the blue cuts through smoke better than white light... the store was waiting to test them out in a smoke house (the store is owned by firefighters) but they haven't been able to try it out yet.
Is this true?
Or is the flashlight supplier blowing smoke? (pun intended)
I looked for a previous discussion on this but couldn't find it.
Replies to This Discussion
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Permalink Reply by Steven Fox on
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I know from Search and Rescue that blue lights help illuminate blood. I never heard it cutting through smoke. Be intresting to test though :)
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Permalink Reply by Matthew Powers on
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I have a helmet mounted flashlight that has 3 blue LEDs and 1 xenon bulb. I can select between them. I prefer the LEDs in smoke because the xenon is too bright. More light gets reflected and it is like using high beams in the snow/fog. I have used other flashlights in the past and the white light on them tends to be the same as the xenon. Because you are reflecting light from across the entire spectrum, more gets reflected back to you in the smoke. In a dark environment this is bad for vision. The blue LEDs will only reflect blue wavelengths back. This means that not all smoke will reflect light back, in fact it will absorb your light. Your light will not make it past any particle that gets in its way, so as John said, nothing "cuts through" smoke, but the lower reflectivity of the blue lights will allow you better vision in a smoky environment.
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Permalink Reply by Jack/dt on
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Matthew,
It might be that the xenon bulb is a more concentrated beam, which means that it would reflect back more strongly than a somewhat more widely distributed beam (LED's). (Your analogy of highbeams confirms this since highbeams (higher candlepower) are designed to throw light further out (illuminate at a greater distance) while low beams (lower candlepower) are designed to illuminate a wider, closer area.) Or it may be that the xenon light has a stronger candlepower.
As for reflectivity, smoke is comprised of particulate matter that tends to be dark/black by nature, which has an albedo near 0, in other words it doesn't reflect light, it absorbs it. Compare the difference between real smoke and theatrical smoke, theatrical smoke has a higher albedo and the reflected light is nearly as bright as the flashlight itself.
As for blue, take a look at the blue light on police (or vollies), it can be as bright as white light. It's really a matter of candle power as opposed to color. A bright blue light can be as blinding as white.
In a smoke filled room, the particulate matter is going to absorb light waves, starting from the shortest (higher frequency) violet to the longest wavelength (lowest frequency) red (remember ROYGBIV?) . Crawl through a smoke filled room with zero visibility and you can be nearly on top of the fire before you see it (you'll feel it sooner since heat is infrared wavelength) and it appears orange/red. Since red has the longest wavelength it can travel further and has a greater ability to do so before being totally absorbed. (Thermal Imaging Cameras operate at the infrared range, above the wavelength of red which is why you can see through smoke.)
Based on this, white light (full spectrum) should penetrate a greater distance from you and be seen from a greater distance by you than just blue light, as blue is more readily absorbed.
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Permalink Reply by Bekks on
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I should clarify about the store... the "salesman" I refered to was the flashlight supplier for the store (not the FF/salesmen that own/run the store).
They stocked the blue (think it was a Streamlight) helmet light based on what the supplier said... explained to me why it's light was blue, and said they were curious themselves to see if it actually worked or not.
They didn't want to say it worked without testing it themselves - one of the good things about a store owned and run by firefighters... they didn't want to sell it without testing it themselves to verify the supplier's claim and risk another FF's safety.
That said, being busisnessmen, they put it on the shelf in case someone wanted a blue LED flashlight.
They did say they are going to test it (likely when their dept. has training in the local training tower).
I will check in with them in the future and see what their results were.
Until that time, I was curious to see if anyone else had seen this, heard of this, tried it, etc....
Interesting discussion so far, thanks for your posts!
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Yah, the Streamlight website says their blue LED lights are used by forensic investigators for that very reason.
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I've seen the Fox-fire helmet lights have all white LED and 2 to 4 green LEDs mixed in... not sure what the green ones are for... maybe to offset the colour of the "white" LED to boost it to a proper full spectrum??? (just a wild guess).
Yah, with smoke being a big cloud of particles, it's like a moving wall... unless you have x-ray vision (or a thermal image camera squished up against your mask) nothing is gonna "cut through" it.
I guess the best bet is to hope that you see in between the gaps or less-dense bits and the vent crew hits the right spots.
Sounds like "full spectrum" ("white") light is still the way to go...
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Permalink Reply by Rusty Mancini on
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My department issued every member with the Fox fury command 20 series. These lights have proven to be very affective in cutting through smoke. According to the manufacture the green LED's in their quote! Green LED's are most suitable for cutting through smoke, increasing detail in ones environment, and enhancing depth perception and color rendition.
I have personally used this light and so far..., it's been the best light I've have ever seen to cut through smoke. Their great for writing down info at night, sure beats having to hold a flashlight under your arm pit while trying to write. Their expensive, but what isn't in this business? Would I purchase another box full, you bet I would!
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Permalink Reply by lutan1 on
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I would have thought the only light to cut through smoke is daylight AFTER the place has been ventilated...
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That is the light I was thinking about getting when my department issues us our new helmets...
Good to hear you like them.
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You wont be disappointed. These lights are great for searching for victims, roof work, mva's, salvage and overhaul, and many more uses. Our members love them and thanked us repeatably for them.
Hands free is the thing as well. It eliminates one guy standing there holding a flashlight ,and adds one more set of hands. On mutual aid calls you can always tell where are folks are, you cant miss them from the lums. that the light puts out.
No I'm not a sales rep. for them, I'm just satisfied that the money we have spent on them was well worth it, and from the safety aspect as well!
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Permalink Reply by Derek R. on
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Hi Rusty.
Just wanted to ask you a couple questions. We have a "demo" at our dept. Noboby has tried it yet because we just aquired it. One question is: Did you, or do you, have any trouble with the access battery wire that hangs free? And My other question is, have you had any problems with the battery pack slipping off your helmet?
Right now I'm, using the Streamlight vantage led, and must say that I'm happy with this one. Mind you, it's a bit more pricey than the Fox Fury. but if I find a better light for less cost, then I'm for it.
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