Airport X-Rays

Discussion in 'Travel' started by arthur_gottschalk, Mar 29, 2020.

  1. I've done much of my photography abroad. I only shoot film and I'm worried about the latest scanners for carry-on bags and the reluctance of personnel to hand check film. So I've decided to buy film in-country and have it processed there. I'll either wait until it's done or have it sent to me. In some countries this will be easy, like France, but in others, like India and Morocco. less so. But I would think this creates an opportunity for professional labs to sell and process film for tourists. How can we encourage that?
  2. Film is costly , unreliable ( outdated, not kept cool, perhaps previously x-rayed), and processing is infrequent, and of greatly varying quality in the third world. IN the UK and europe, less risky.
    shoot digital and set the camera to process it as film, or set computer in postprocessing to process a film. Works for me.
  3. Modern gate security x-rays operate like an electronic flash - the x-ray tube emits only a flash of x-rays, and the sensor below the belt captures the image and displays it on a screen. The x-ray dose is so small it can't fog your film, even after multiple passes. These machines operate this way to make sure the security staff that work around them 8 hours a day don't receive risky exposure to x-rays. The older machines had a continuous beam x-ray tube, meaning the beam was on all the time, and keeping staff exposure low required a lot heavy shielding around the x-ray tube. When airport security ramped up after 9/11, putting a lot of those old machines close together like they are today caused floor weight-load issues, hence the development of the newer pulsed machines.

    Of course, there's a down side. The more modern countries wanted all airports everywhere to implement x-ray examination of carry-on bags. That led to the older continuous beam machines being sent to small, remote airports, those with low traffic. One of these machines might cause some fogging of film, especially if the film has to pass through several such airports. Flying only through major airports won't pose a meaningful risk to your film. The only risk from gate security x-rays would arise if you were flying into and/or out of remote airports in far flung parts of the world.

    BUT THERE IS A REAL X-RAY HAZARD! Never put your film in a bag that gets checked at the ticket counter. Most US and European airports today put checked bags through a CT scan that most definitely will ruin your film. NEVER PUT FILM IN A BAG TO BE CHECKED.
  4. david_henderson


    Interesting that you consider the risk of X-Ray damage to be greater than the combined risks/inconveniences of finding film in a place you don't know; finding processing in a place you don't know; maybe having to use a sub-optimal film; risks of processing error by a lab you don't know; risk of loss in transit to you by a lab/postal service; having to wait days for processing because many labs won't find it sensible to run processing every day. I think many would disagree with you - and I certainly would.

    I would not hold my breath waiting for the number of film sellers and labs on a world scale to increase dramatically unless there is a very large increase in film usage globally. I doubt whether there are enough photographers thinking/behaving as you describe to drive film & lab availability.
  5. Both Ilford and Kodak have issued warning about the effects of the new scanners. If anyone needs a further warning, I suggest looking at a recent test posted on the EMULSIVE website, which concluded "these scanners lead to significantly fogged film" after one pass through the scanner at Amsterdam's Schiphol airport.

    Unfortunately, these warning lead me to conclude I will have to do most of my photography close to home or in places accessible by car without air travel. And yes, film is expensive, but so are hard drives, scanners, computers and digital cameras and lenses. At any rate, I don't enjoy computers and would give up photography if that was all that was available to me.

    Perhaps it will eventually be possible to widely establish hand checking of film, but I'm not holding my breath.
  6. OK - here's more than you wanted to know. :^)

    I'm not surprised at the EMULSIVE article. I ran measurements at McCarran Airport in Las Vegas a number of years ago. I managed the radiation measurements program at the Nevada Test Site until I retired, and we were finding employee's dosimeters designed to monitor occupational exposure to radiation showing x-ray exposures that shouldn't happen at the site (no x-ray sources at the time). We traced it to the CT scan system at the airport - people were traveling for business and taking their dosimeters with them (the dosimeter was usually attached to the lanyard used for the employee's ID, which was needed during the travel). I got permission from TSA to run test dosimeters through the gate security machines and the checked baggage scanners, although they would not tell me the voltage settings they used for each kind of x-ray machine. When I was done, I told them what the voltages were - they were not pleased, but I agreed to keep it confidential. We found that we had to put a single dosimeter through the gate security scanner almost 50 times to get an x-ray measurement that could be identified as different from natural background with reasonable confidence. A single pass, or several passes associated with long distance travel wouldn't deliver a high enough dose to make a visible difference in film performance, even for quite high ISO film.

    On the other hand, the checked baggage scanners were different ballgame. The CT scan uses a rotating x-ray tube that encircles the bag using a continuous x-ray beam and digital imaging to "see" the bag's contents. Then a computer analyzes the image looking for specific characteristics that might indicate something that shouldn't go on the aircraft, and if detected, the bag would be opened and hand searched. The system allows a lot of bags to be scanned without opening them unless warranted, saving a lot of time and a lot of cost. But anything radiation-sensitive takes a hit in the process. We saw an average of about 75-100 millirem per airport baggage scan. A typical round trip between Las Vegas and Albuquerque or Las Vegas and Washington DC (most of our employee travel) resulted in about 175 millirem and was readily identifiable as not only caused by x-rays, but also by x-rays of the energy (voltage) we found the airport scanners used.

    Looking at the film fogging issue one way, one could conclude that taking film in a carry-on bag is safe; it's only necessary to avoid putting film in baggage to be checked. But that's only valid for travel around the US, western Europe, and probably plenty of other places I don't know of. But if you get off the beaten path, going through remote airports in places other than the US and western Europe, you are taking your chances. After 9/11, everyone agreed that gate security needs to be effective everywhere for the airline security system to be effective, but there were lots of places with no gate x-ray equipment and no funding to get them. The solution was for the major airports to deal with the floor loading issue caused by the old x-ray machines by replacing those machines with the new pulsed beam machines, and the old machines they replaced were given to smaller, remote airports all over the world. They are still out there, and it's difficult to predict where you might encounter them.

    Another bit of trivia, although it's not trivial. Anything mailed to any federal agency in Washington DC, or to any of a large number of people associated with the federal government, was put through a security system to guard against threats like anthrax. When I was still working, such mail was sterilized by irradiating the unopened mail using an electron accelerator to deliver megarad doses, way beyond fatal to a human being, enough to be fatal to any living material, without damaging the paper or ink on it. Even developed film wouldn't survive - at such doses, there'd be no recognizable image left on developed slides or negatives. I don't know that this practice is still used - technology may offer an easier way to accomplish the same security these days.
  7. Thanks for that Bob. Now my next question: Is film sent by mail internationally x-rayed? I can imagine buying film abroad and mailing it home for processing. That could be a solution.
  8. My knowledge about this is undoubtedly out of date. We used to send radiation-sensitive dosimeters to overseas locations routinely, but we never used mail. We shipped only by DHL because they were - AT THAT TIME - the only international shipper that did not accept shipments of radioactive materials. All of the others handled regular shipments of radiopharmceuticals and industrial devices containing radioactive material, and if your shipment happened to be placed next to one of them, your shipment would be irradiated. We learned this lesson the hard way - a Fedex shipment of ours spent a night in a terminal in Boston and showed clearly that it was irradiated. Fedex's tracking system was complete enough to be able to tell us that our package was in a room next to another room in which a radiography source was stored at the same time, both of them placed opposite each other against the wall that divided the two rooms. I do not know if DHL still declines radioactive shipments. One disadvantage to DHL is the extent of their service - they don't have DHL-operated pickup and delivery in anywhere near as many locations as the other carriers. It so happened we were shipping from a DHL-served city to another DHL-served city. If your shipment originates in or is delivered to a place not directly served by DHL, they will turn the package over to another shipper that does serve that location for pickup and delivery, and the radiation-free aspect is lost.

    It is my understanding that most (and maybe all) cargo carriers sometimes put their packages in unused cargo space in commercial passenger planes. I expect that such freight would have to go through the same security screening as the baggage that goes in the aircraft's cargo hold.

    I'm afraid there's no easy answer to getting film around the world these days.
  9. TSA claims that theirs are safe up to ISO 800.

    I have never tried taking TMZ or Delta3200 on a trip, but I understand that they are
    especially sensitive.

    Also, as I understand it, some of the instant films, such as Instax, are
    also more than usually sensitive and should avoid X-rays.

    As well as I know, TSA rules say that they will hand inspect, usually
    with the mass spectrometer test, if asked. Other countries don't seem
    to allow for that, at least for ordinary speed film.

    If asked, and they usually don't, I tell them that I use a special developer
    that increases the speed to more than 800. (I commonly use Diafine.)

    Also, color films should be more sensitive, at the same ISO rating.
    Each layer only gets about 1/3 the light, so has to be somewhat more
    sensitive than it would for a black and white film.

    I believe that the usual airport scanners use (at least) two different X-ray
    energies, to help separate different materials. I don't know that those
    energies are, though.
  10. Here is the data sheet for what looks like the usual carry-on scanner,
    though seems to be sold for other use, such as building entry:

    It mentions 100kV and claims safe up to ISO 1600.

    Also it claims to work through 14mm of steel.

    I did one time have a FilmShield bag in my carry on luggage.
    After going through the scanner, when they noticed it, they then ran the FilmShield
    bag though alone, and were satisfied with what they saw.
  11. "I would think this creates an opportunity for professional labs to sell and process film for tourists. How can we encourage that?"

    The bottom line is that not many people shoot film anymore. I use to have a metal case that was x-ray proof, but even that became a hassle at the airports.
  12. Note from the above links, the scanners claim to work through 35mm of steel.

    I suspect that cases aren't very X-ray proof.

    I didn't look up X-ray absorption numbers, though.
  13. The most valuable characteristic the gate security scanners have for film users is the short duration of the x-ray exposure. The x-ray tube charges up, the operator moves an assortment of items on the conveyor belt into the machine, and then takes a snapshot of all that stuff using x-rays. The image is captured digitally and displayed on a screen for the operator to examine. The tube flashes the x-rays literally like an electronic flash on a camera - a burst lasting around 1/1,000 second.

    The energy of the x-rays used for the scans has to be high enough to penetrate the kinds of items the security system wants to detect, even if the items are hidden inside some sort of container. Any container too dense for the x-rays to get an interior image will be hand-inspected - opened by or in front of security personnel.

    The bottom line is that the dose RATE - the intensity of the x-ray field - is fairly strong. I estimated a dozen or so rad/hr (not a terribly precise estimate) - a dose rate no one would want to spend any time in. The key is that the dose rate exists for only a 1/1,000 second or so, meaning the total dose the scanned items receive is a fraction of a millirad, i.e., less than 1/1,000 of a rad. The digital image capture is what makes this all possible.

    As I said some time ago, these machines are the solution to a problem created when airports were required to increase security for passenger aircraft. Bringing a collection of the older types of x-ray machines to a central security checkpoint created a weight loading problem for air terminal floors that were never designed to carry that much weight. The weight came from all the lead and steel shielding necessary to reduce the dose rates around the machines for the people who worked at them all day. Going to the pulsed (flash-type) x-ray systems allows them to dramatically reduce the amount of shielding and still get the images they need without causing high doses among the gate security workers.

    Unfortunately, some of the old style x-ray machines are still in use. When the western world ramped up airport security, they wanted the rest of the world to do the same, since the security system is only as strong as its weakest entry point. Smaller, poorer countries were agreeable to joining the process, but didn't have the x-ray hardware or the budget to acquire some. The solution was to give the old machines being replaced across the US and Europe to the countries that had none at all. So taking film into and out of some countries includes the risk of it going through one of those old machines, and they are distinctly unkind to film.
  14. I found a discussion on Film-Shield bags, and added to it:

    Domke Film shield bags

    Ohterwise, mostly we should continue here.
  15. The US machines from not so many years ago were fairly safe for film.

    As well as I know, in some countries high dose machines were used for carry-on scanners.

    Additional data on newer ones is that they can detect AWG 39 (American Wire Gauge),
    and 4096 gray levels. ;

    If the difference between 0 and 1 is 35mm of steel, then between 4094 and 4095,
    and absorption being exponential in thickness, it should be able to
    see log2(4096) or 1/12 the thickness, so about 3mm of steel.

    I have to find a table of 160kV absorption coefficients for different materials.
  16. I think I understand a little better now.

    First, the usual way absorption works, for light and X-rays, is that there is more absorption close to a resonance, or in the more specific case, when there is an electron transition at the photon energy. Heavy metals have inner-shell electrons with binding energies close to traditional X-ray energies. Lighter elements have much smaller energies, and so are not strongly absorbed. This is for more traditional energies around 20keV.

    But now scanners are up to 160keV. The higher energy means that absorption is reduced.
    It is so much above the electron energies that all electrons look the same.
    Absorption, then, is pretty much on electron density, which equal proton density.

    Heavier atoms have more neutrons, so are heavier in proportion to atomic mass,
    but the increase in electron density is much lower.

    Note that this means less absorption by silver and bromine, too, so less cause to expose film.

    To image the result, though, the X-rays have to be absorbed, and converted to a visible image.
    I am not so sure how they do that, but that is the most important part.
    hjoseph7 likes this.
  17. Back in the good old days (you remember them, don't you?) I always used a lead bag to carry film. Worked perfectly for years but eventually they would spot a dark era of the scan and investigate. Now they always want to look closer and send the film through the scanner unprotected.
  18. If I am not in a rush, I ask (in the US) for hand scanning. But sometimes I do sent them through.

    As above, last year I had them put the lead back through with film. They didn't need to take it out,
    and I could see, just a little from the angle that I was at, that they do see through lead bags!

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