TIC and Glass

[backdraft663]

Anyone know why you cant see through glass with a TIC?

[SamsonFCDES]

Glass reflects and blocks the IR spectrum I believe.

[CrossBro1]

Glass reflects and blocks the IR spectrum I believe.

Sounds about right. Also polished metals like brass, aluminium, etc., will also reflect the IR spectrum.

[firenresq77]

I believe a pool of water does, also.........

[stm4710]

You see the heat of the glass not the image on the other side. In the IR world glass is no different than concrete. Same with water etc.

If your board one night and have a stainless steel pump panel stand infront of it looking at it with a TIC-----might see a ghost!

[torichardson]

This explanation could be very technical but I will keep it simple because all of that technical stuff is not going to do you any good on the street at 3:00 in the morning.

Fire Service TICs (Thermal Imaging Cameras) work by detecting LWIR (Long Wave Infrared) that has a wavelength of 8-14 Microns.

Based on this wavelength, LWIR is capable of cleanly passing through some things and it will be absorbed or reflected by others.

LWIR CAN cleanly pass through:
air, smoke, fog

LWIR can NOT cleanly pass through:
water, ice, glass, plastics, metals, and any most "solid materials"

I am going to post some pictures with additional info to demonstrate some examples.

I can't tell you the number of times I have seen firefighters misusing a TIC because they do not truly understand how they operate. Trying to use them to see through glass and water to locate victims is classic example.

For additional information on TICs here are some other recent discussions and websites that will help:

http://cms.firehouse.com/forums2/sho...threadid=56676

http://cms.firehouse.com/forums2/sho...threadid=55266

http://cms.firehouse.com/forums2/sho...5&pagenumber=1

www.safe-ir.com

http://thermalimager.bullard.com/index06.cfm

backdraft663, thanks for your question, I am sure there are many others out there who had the same question and will learn from the response.

If anyone has an experience with a TIC, good or bad, that everyone can learn from PLEASE share it.

Live & Learn, Learn So You May Live.

Good Luck, Stay Safe,

[torichardson]

Here is an example of how TIC works with water.

The visible light your eye uses will pass through the water to a certain extent so you can "see through" water with your eyes.

The LWIR the TIC uses will be absorbed or reflected by the water so the TIC can not "see through" water.

[torichardson]

Here is an example of how you can get a reflection or "Ghost" as stm4710 put it.

The LWIR is being reflected off of the side wall which is covered with a reflective aluminized insulating material.

This could be a very common scenario inside of a commercial building. Better hope you can figure out which door is really there!

If you are not sure if you are looking at a relfection with a TIC:

Wave, if the Firefighter waves back chances are it is a reflection.

Change your viewing angle, the reflection may go away or you may be able to pick up on it being a reflection.

Physically check it out, when all else fails you may have to physically check it out.

[torichardson]

Here is an example of plastics.

This is an example of a "plastic" door that you may encounter in a commercial building.

Once again, the visible light your eyes use will "pass right through it".

However, the LWIR the TIC is trying to use is being absorbed or reflected.

*Exception to the Rule*
LWIR can pass through some thin plastics. If you put a trash bag over your TIC, it will "see through it"

[ffemtreed]

Our new K90 TIC has an Overlay feature that is supposed to help with looking through glass. I personally havn't tried playing with it looking through glass so I can't comment on its effectivness. I persnally think its just another button to confuse people.

I would rather the camera have just one on/off button and thats it.

[CJMinick390]

Excellent pictures Capt. Richardson. They really show what you are talking about.

[captstanm1]

The heat is reflected back from the window. You can not see through the window (flames) but you can see what is also termed as a "halo" around the window.

[Fire304]

Originally posted by ffemtreed
Our new K90 TIC has an Overlay feature that is supposed to help...

The "overlay" in ISG cameras is simply a visible light camera which is mixed with the signal from the TI sensor. While it will "see" through glass and it will also add some texture to your TI vision, it only works when you would be able to see anyway, smoke will obscure it resulting in a TI image only.

Basically, if the overlay feature is working you don't really need the TI unless you are looking for hotspots. If you're in a place where you need the TI the overlay will not help you until visibility improves.

[Weruj1]

what great photos .........and good information !! thanks Capt !

[torichardson]

Here is some more info/examples on glass & TICs.

Remember, when it comes to glass basically 1 of 4 scenarios will come into play.

Scenario #1 - You can have objects and/or victims behind the glass in which case you will not see them with the TIC. However you may “see” reflections from the same side you are viewing from. There is one exception to that rule which involves old single pane glass, see Scenario #2 more info on that exception. (Photos for Scenario #1 Below)

[torichardson]

Scenario #1 - Can't see anything on the other side, getting a reflection from the side you are looking from.

[torichardson]

Scenario #2 – You have an old single pane glass window, due to its construction LWIR can pass through it. In the photo below you can actually see flames from a fire through an old single pane window. This obviously can be confusing if you are not sure what you are looking at.

[torichardson]

Scenario #3 – You can have a victim or object that is in direct contact with the glass, which will produce a "heat signature" on the outside glass surface due to heat or energy being physically conducted through the glass. This will produce some form of heat signature that may or may not be recognizable. Example: a victim is leaning against a window or glass shower door, after 2-5 minutes heat will pass through the glass to produce “an image” when viewed with the TIC on the other side.

Sorry don't have a photo handy for this one but I will get one and post it. I am sure you can get an idea of what it would look like from the description.

[torichardson]

Scenario #4 – You have a fire that is heating up the inside of a house or room. The fire will heat the glass/windows, the windows will get hotter which you should be able to detect with TIC. Remember you will not see the flames or fire directly but the heat that is being transferred to/through the windows. Also remember newer energy efficient double & triple pane windows will retain more of the heat and may actually hide a substantial heat condition.

Top Photo - Heavy heat condition behind both windows. Working Fire!

Bottom Photo - Minor? heat condition behind middle window. Not Sure!

[Jonathan Bastian]

Originally posted by backdraft663
Anyone know why you cant see through glass with a TIC?

Just like light doesn't go through most materials, neither does infrared. Remember that in general, your TI wants to see surface temperatures. Glass has a surface, and therefore, the TI tries to create an image of it. It also happens that glass is reflective of heat as well, and therefore can show nearby heat images.

The ability of different energies to penetrate different materials is based partially on wavelength. Just think about how AM and FM radio signals act differently, or how your FD radios work great in some situations and terribly in others. The IR wavelength that your TI uses penetrates just a few solid materials. In reality, that is not much different than your eyes...they only see through a few solid materials as well.

It's just that the solid materials are different for TIs and human eyes. The best way to adjust to this difference is to regularly use and train with your imager.