sniffers, puffers and trace-detection



If your friend is a regular member of a trap & skeet club and drives you to the airport then you’re at risk of setting off the explosives detectors in the pre-boarding security area.   If a suspect is arrested and handcuffed by or rides in the car of a policeman who has recently fired a firearm, then any nitrocellulose based gunshot residue (GSR) to be collected as evidence has probably just been cross contaminated.   Actually GSR or other things that can be confused with it are so common place that police CSI (Crime Scene Investigators) seldom even test for it any more.  Instead they usually look for priming chemicals like barium nitrate, antimony sulfide, lead styphnate and magnesium.    In recent times some instruments used by airports and by crime scene labs to detect illegal drugs and explosives, have both expanded in capability and shrunken in size.   These instruments are extremely sensitive; sensitive enough to detect the minutest particles of residue on clothing from nitrate explosives, toxic chemical gasses, biological pathogens or illicit drugs.  This post proposes to cut through some serious techno-babble, but still give the reader a casual understanding of what happens when he or she gets “sniffed” by airport security.


photo by Dominikmatus

The name chromatography {Gk: color / to write} comes from a Russian botanist who a century ago was trying to separate chlorophyll, carotene and xanthophyll plant pigments.  Chromatography is a laboratory process of separating mixtures to determine their composition.   It is an examination usually preformed upon very small samples.   During separation one component of the sample remains stationary and stays put while another becomes mobile and moves away.  Preparative chromatography sort of reduces or purifies a sample before analytical chromatography might take over to identify individual constituents on a molecular scale.   Column, planar and displacement chromatography focus on the stationary component of a sample and might quantify movement through a medium.   Gas, liquid and affinity chromatographic techniques focus on the mobile components or mobile phase of separation. There are many types of detectors used in mobile (gas and liquid) chromatography.   A detector (either a destructive or non-destructive type) is a device used to visualize components of the mixture being eluted from a sample.  A mass spectrometer is a destructive detector that excites or ionizes vaporized particles – perhaps with an electron beam, and then separates or sorts out these ions in an electromagnetic field (analyzer).  A flame photometric detector is destructive also because it burns things up in a hydrogen flame, reading the light emitted through an optical filter to get its results.   A flame ionization detector works in much the same way but measures the conductivity of the flame.    Evaporative light scattering, atomic-emission and nitrogen phosphorus detectors are also destructive of the eluent (solvent) and analyte (subject in question).   Non destructive type devices would include photoionization, electron capture, refractive index, fluorescence, UV and thermal conductivity detectors.

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Traditionally chemical analyzation by chromatography in a laboratory has been time consuming and expensive.   This situation is much changed today as better technology has become available.   As some detectors are sensitive only to specific types of substances, modern compact instruments might incorporate multiple gas chromatographic detectors.  The mass spectra collected by those detectors is  analyzed by a logic unit running programmed software.   Not all of this equipment is created equal; sensitivity ranges from detection at particles per million – to particles per trillion.

 9892_FebToday thousands of people per minute and separately their luggage, can be scanned in an airport.   Not all airports can afford ‘sniffing’ equipment but the large International ones are likely to be well equipped.   By 2007 about 95 “puffer” machines were installed in 34 large airports in the U.S.   A “trace portal machine” (or “trace-detection portal machine”) detects compounds on a molecular level using either ion mobility spectrometry or mass spectrometers, to detect extremely small “traces” of explosives and illegal drugs.  These machines got the nickname “puffer” from the fact that they shoot little jets of air at passengers, freeing particles from clothing that can then be sampled.   (Airports where these were installed include: ABQ, DEN, PHX, DTW, JFK, MIA, SFO, SAN, PBI, LAX, SLC, DFW, IND, PIT, DCA, LAS, TPA, PDX  and BOS).   Not nearly as many puffer machines were purchased by the TSA as was expected.   At $160,000 apiece these puffers were power hungry, unreliable / maintenance demanding and loud but most of all – slow (screening only about 3 passengers per minute).

*Added April 2015

 The puffer machines were soon junked or retired as much superior spectroscopy machinery became available.   Much more affordable, robust and exponentially faster technology exists today that performs its function without a spectrometer.  Almost instantaneous molecular spectroscopy is now accomplished using fiber optics and PC controlled synchronized programmable laser detectors.  Using (IR) wavelengths in the mid to far- infrared range between 3 and 20 um, rapidly tunable lasers can scan up to 100,000 wavelengths per second.   This means that a simple scan for a particular substance can be preformed in milliseconds or a very high resolution scan can be preformed in microseconds.

Of course airports are just one example of demand for snifters or gas chromatography analysis.   Customs officials at ports of entry, chemical factory employees, Coast Guard, military and law enforcement alike, all benefit from improved trace-detection capability.

If humans had superb sight then we might be able to see the little aurora or cloud of gas and dust particles surrounding us, that we permeate perpetually.  Some of the newest and most promising threat detection already uses lasers to identify gasses that surround humans as they stand in a booth.  Fluorescent polymer technology using ultraviolet light to test for reflection, absorption or excitation of another electromagnetic wavelength, is making bold strides these days also.   It probably won’t be long before x-ray metal detection and chromatography are simultaneously and expediently accomplished by the same piece of scanning equipment.



According to ‘’ dogs still have by far the most developed ability to detect concealed threats.   A trained dog can walk through a crowd of a thousand people and easily find a piece of contraband.  Some dogs can smell disease in people.  Digital gadgetry simply cannot match that ability yet.   Sure some machinery has the sensitivity to trace molecules in miniscule parts per trillion amounts, but samples for the instruments must usually be collected very carefully. A dog must have both a disposition for police work and a very good nose.   Scientist in South Korea have decided that only 30% of the dogs cloned from “Chase” (a famous contraband sniffing Golden retriever) have the level of smelling capability required for the job.   Dogs can’t work continuously.   Like their human handlers they need water, meals, toilet breaks and sleep.  It takes time, money and effort to train a dog.  Sniffer dog training involves using behavior modification techniques on a positive reinforcement schedule.  The dog handler as well must be skilled.

In Israel some instruments that look like airport metal detectors or full-body scanners might actually house a bunch of mice.   Apparently mice have a developed sense of smell also.  As air blowing past transient passengers is pumped into their chamber,  the trained mice will respond to threatening (qualifying) odors.   When several mice flee to their safe chamber an alarm goes off.  Presumably the teams of mice are conditioned to react to individual odors by using a negative reinforcement conditioning schedule, where perhaps they learn to associate trace odors of common explosives with a mild but unpleasant electric shock from the floor of the primary cage.   These machines that mimic full-body scanners are actually mouse hotels that are home to 3 trained teams of 8 mice each, that work in 4 hour shifts.   The machine is programmed to blow air samples into an alternate chamber on a 4 hour schedule, giving the off-duty mice 8 hours to eat, sleep and relax.

Some interesting video links:

Safran ‘Advanced CTBased Explosives Detection’ :

FLIR ‘Fido NXT launch video’ :

POC video :

One wonders what the contraband detection repertoire of dogs, mice and digital snifters might actually be.   There are a large number of illicit drugs including: psychedelics –like PCP, DMT, LSD, mescaline and cannabis; depressants -like inhalants, barbiturates, tranquilizers and narcotics; stimulants –like amphetamines / methamphetamines, ecstasy (MDMA) and cocaine.   Many if not each of these examples might require a separate trace detection profile, meaning that the animal has to be conditioned to a unique stimulus, or chromatographic instrument be equipped with specialized detector and programming.   There are about 800 uniquely identifiable explosive compounds.  Trace detection here can be simplified somewhat because many but certainly not all explosives are nitrate based.   Additionally, nitrate based explosives like PETN, RDX, HMX and Semtex are hard to detect because they have very low vapor pressures (meaning here that, they surrender detectable molecules to the atmosphere very slowly).   Liquid explosives likewise, can be very hard to sniff.   Then, on top of all of this there is a long list of chemical and biological threats for security to be on watch for.

If not already then in the near future airports may employ both passenger profiling and tracking of passengers in terminals by means of cell phones and Bluetooth wireless technology.   Whereas old fashioned electronic lie-detectors use galvanic skin responses to make a determination, new technology promises to achieve the same feat from a distance using thermal-imaging cameras.


Biohazards, select agents and chemicals

All toxins or “biotoxins” are understood to be the product of plants, animals or microorganisms (like bacteria, viruses and fungi).  The term “toxin” is reserved for poisonous substances that are produced by living cells or organisms but the term “toxicant” is applied to poisons not produced by living organisms.   Hemotoxin might come from the venom of a rattlesnake or neurotoxins from Black Widow spiders, scorpions or jellyfish but these toxins are not on the “select agent” list.  When pathogenic viruses, bacteria or fungi are deliberately dispersed by human activity then these “biological agents” are a tool of “bioterrorism“.   There are about 70 or so select agents and toxins on the National Select Agent Registry.  Familiar sounding biotoxins would include the names: anthrax, botulism, cholera, ebola, E.coli, hantavirus, plague, ricin, salmonella, smallpox, tularemia, typhoid and typhus.



Poisonous Gasses – Added April/ 27/2015

Weaponized chemicals began making their debut a century ago during “the Chemist’s War” or “the Great War”.   Advancements in modern chemistry brought poison gases to the battlefields of WWI.   Easily more nefarious than the machine guns, tanks, aircraft and submarines also introduced during this conflict; gas was responsible for only about 4% of the total causalities in the epic slaughter.   An estimated 88,500 to 100,000 deaths and 1,241,000 non-fatal casualties were caused by gasses.  The greatest numbers of victims appear to have been Russian.  Many gas victims that survived the war would later succumb to tuberculosis due to scar tissue on their lungs.  In 1914, France, not Germany was the first to use a weaponized gas.  It was a non lethal lachrymatory irritant (tear gas).   Germany was to respond later in the same year with a similar irritant, neither side in conflict yet with the 1899 Hague Treaty that prohibited the use of toxic, asphyxiating gas.  At least twenty different chemical compounds were used as weaponized gas during the war; several of them were less than lethal.   The five most famous gases of WWI were chlorine, chloropicrin, cyanide, mustard and phosgene.

Repelled by the consequences and unpredictably of gas warfare, opponents in later conflicts predominately avoided its use but maintained large, ready to use stockpiles of gas nonetheless.

* The Italians used mustard gas in Libya in 1930 and from 1935 to 1940 they dropped about 500 tons of mustard, arsine and phosgene bombs on Ethiopia.

* Japan used phosgene and other gases against China in WWII.

* The Germans might have used some mustard agent against the Poles and Russians in a couple of incidents in WWII.  Hitler himself was a victim of gas during WWI.

* The Allies maintained gas munitions and the aircraft needed to deliver in a constant state of readiness throughout WWII.

* Iraq deployed poisonous gas against Iranians and Kurds between 1980 and 1988.

Weaponized chemicals are generally classified in one of four categories: blistering agents, blood agents, nerve agents and pulmonary agents.  A brief introduction to some of these follows.

Chlorine was the first potentially deadly gas to be used (by the Germans in 1915) but it was importantly a powerful irritant to the eyes, nose, throat and lungs.   Visible from the trenches, the gas made green smoke clouds when released.   Chlorine was also the most produced gas of the war, followed by phosgene.

Chloropicrin is not especially deadly, but it makes a good teargas and causes victims to vomit profusely.  Chloropicrin is made by mixing picric acid with a chlorinating agent.  The Germans used it against the Italians on the Italian front but it was a Scottish chemist that discovered it in 1848.  Today chloropicrin is used on soil as a fungicide and pest killing fumigant.

Cyanide was the least produced but one of the most lethal gases used in WWI.  Hydrogen cyanide is generally made by mixing methane and ammonia using oxygen and a platinum catalyst.  Although it was first created around 1706 by a German chemist in Berlin, the British were the first ones to deploy it (in 1915).  Twenty years later the Nazis did murder many Jews with non-weaponized Zyklon B.   Zyklon B itself was an odorant removed version of the common commercial pesticide Zyklon.  Zyklon contained liquid prussic acid (hydrogen cyanide) which vaporizes when mixed with water.  Respected as a poison since Napoleonic times, prussic acid in useful forms like Zyklon was normally applied as a fumigant used in ships and buildings to kill rodent and insect pest.

Mustard gas was a vesicant or blistering agent, effective against troops wearing gas mask because it was absorbed through the skin.   Its effect was agonizingly painful.  Not particularly lethal, the incapacitating agent only killed about 1% of the victims exposed to it.   It did however spell the demise for 56,000 Russian soldiers on the Eastern Front that were caught unprepared and ill equipped to handle it.   Developed well before the war, mustard gas wasn’t deployed until late in the war (1917).  It was often made with sulfur dichloride and ethylene, but several other chemicals could be used to make a similar vesicant.   Mustard gas gets its name from its smell which is similar garlic, horseradish or mustard.   Mustard gas condensates to a heavy oily residue that puddles up on the ground and stays for a long time; this persistence makes it a useful battlefield denial tool.   Several mixtures of sulfur mustard were to be deployed by both sides.  Allied designations for mustards made by different processes were H, HD, HL, HQ and HT.   The later variants called mustard gas were frequently based on nitrogen rather than sulfur.   Until recently the U.S. maintained huge stockpiles of mustard gas.  Iraq used it against Iran between 1983 and 1988.   

Phosgene was first synthesized by a chemist some 200 years ago.  A deadlier gas than chlorine it was sometimes mixed with chlorine which assisted in its dispersal.   Introduced to the war by the French (1915) and used by both sides in the conflict phosgene was much deadlier than the more notorious mustard gas.   On the Western Front it was responsible for perhaps 85% of the battlefield deaths attributable to gas.   Phosgene is very easily made from carbon monoxide and chlorine with exposure to sunlight.   Ultraviolet light can slowly convert chloroform into phosgene.   Heating carbon tetrachloride makes phosgene.   Phosgene is said to smell like musty hay.   An irritant to the skin and mucous membranes the corrosive agent becomes toxic when it causes suffocation by disrupting the blood-air barrier in the lungs where oxygen and carbon dioxide are exchanged.  The Japanese used phosgene (as well as mustard gas and lewisite) on many occasions against the Chinese between 1937 and 1945.

Lewisite was invented by an American chemist and soldier.   A vesicant more dangerous than mustard gas, the arsenic containing agent was produced in volume by 1918 but not delivered to the battlefront before the singing of the armistice.   The Japanese who used gasses against the Chinese on at least 880 separate occasions in WWII apparently dispatched 3,500 Chinese troops with lewisite in Oct 1941.   In the 1960’s the U.S. neutralized much of its Lewisite and dumped it in the Gulf of Mexico.   Some lewisite may remain, awaiting disposal in the Desert Chemical Depot in Utah.   In 2010 some old leftover WWI era lewisite was discovered in a munitions dump in Washington, DC.  Arsine like Adamsite and Lewisite is a gas built upon a simple compound of arsenic.

Adamsite or DM was a riot control gas that was developed during WWI but used for the first time probably in downtown Washington, DC in 1932.    Some 43,000 Depression era-impoverished war veterans and their families were camped out in the center of the capitol, demanding immediate payment of their service certificates by the government.  President Hoover had the squatting protesters removed by force.  Two veterans were killed by bullets and several children were severely injured or killed by the Adamsite gas.

The two decades between WWI and WWII saw the development of a new class of gases called nerve agents.   Nerve agents are organophosphates (phosphorus containing organic chemicals) and attack the nervous system by disrupting nerve communication to human organs.   Generally a victim looses control of bodily functions, becomes epileptic and dies from respiratory depression.   Nerve agents were discovered for the most part by chemist looking for ways to control crop destroying insects.   It was only later appreciated that such compounds might make useful weapons for war.   Nerve agents fall into two broad classifications: the so called “G-series” (developed by German chemist) and the “V-series” (mostly developed by British chemist and at a later date).

The G-series organophosphate nerve gases include tabun (GA – 1936), sarin (GB – 1938), soman (GD – 1944) and cyclosarin (GF-1949).

Tabun was discovered by accident by a German chemist working on insecticides for the IG Farben chemical conglomerate.   Tabun is extremely toxic, smells like fruit and is fairly simple to produce.   The U.S. once produced tabun as did the USSR.   Iraq used mostly mustard gas and sarin, but also cyclosarin and tabun in its 1980’s war against Iran.

Sarin was discovered by different German chemists that were also involved with creating stronger pesticides.   Malathion in some modern day insecticides resembles sarin in action but does not threaten humans directly.   Sarin nerve agent is exponentially more deadly than cyanide for example.   The archetypical nerve gas, sarin elicits these progressive symptoms: running nose, tight chest, constricted pupils, nausea, drooling, vomiting, defecation, urination, spasms, unconsciousness, convulsions and final death.    In the 1950’s sarin munitions were standard chemical weapons for NATO, the U.S. and the Soviets.   The term “weapons of mass destruction” was popularized in the U.S. by President Clinton but its first use came from a 1991 UN resolution to condemn all chemical weapons (especially sarin which was being produced and used by Iraq).   The 1993 UN Chemical Weapons Convention called for the complete destruction of all chemical weapons.   Not long afterward (1994-95) sarin was produced and released on two separate occasions in Japan by some obscure religious sect.

Soman is said to smell like camphor and is stronger and more persistent than tabun or sarin.   Apparently never used on a battlefield, this organophosphate was very similar to sarin in its synthesis.

 Cyclosarin is said to smell like peaches or shellac.   Probably the most lethal of the German (G-series) nerve agents, it was first synthesized in a laboratory during the war but not really developed until the British and Americans found its recipe and began toying with it about 4 years later.   Iraq is the only country that has produced cyclosarin in quantity and the only country to have used it in battle.

The V-Series nerve agents were largely British in origin.  In the early 1950’s British chemist researching improvements in pesticides developed a new group of organophosphates that became known as the nerve agents VE, VG, VM VR and VX.   The main improvements over the G-Series is in the V-Series’ higher persistence and increased toxicity.   There was never much disclosure on these compounds and not much is known about them publicly.    Similar to viscous motor oil, droplets cling to things and do not degrade or wash off clothing easily.   Primarily intended as a battlefield denial weapon with high persistence, VX is highly lethal.   It apparently takes very little (< 750mg) of this organophosphate to kill a person.   The USA put VX gas in landmines, artillery shells, aircraft spray tanks and rocket cluster-bombs.   Similarly the Soviets also fielded equivalent V type gases.

* U.S. disclosures:  In the late 1960’s entire ships filled with VX warhead rockets and other toxic munitions were scuttled in deep water offshore of Atlantic City, New Jersey.  Before 1972 the U.S. had already dumped an estimated 64 million pounds of mustard and nerve agents into the ocean.   A 4,240,000 lb. stockpile of mustard agent at the Aberdeen Proving Ground in Maryland wasn’t completely destroyed until 2005.  The destruction of a similar stockpile in Utah did not begin until 2006.   In 2008 the DOD reported that more than 120 tons of VX had been dumped offshore – somewhere in the Atlantic between New York and Florida.  Much VX and other chemical agents were incinerated on Johnson Atoll (about 860 miles west and south of Hawaii) before that facility was cleaned up and shut down.  Supposedly VX was gone from the U.S.  arsenal by 2008.  In 2010 some fishermen dredged up some old lost mustard ordinance from the waters south of Long Island, NY and had to be hospitalized.

 The Chemical Weapons Convention (treaty) banned the development, production and stockpiling of such weapons since 1997.  Only thirteen states (Bosnia /  Herzegovina, China, France, India, Iran, Iraq, Japan, Libya, Russia, Serbia, United Kingdom & United States) ever officially declared chemical weapons production facilities.  If we are to believe and trust governmental disclosures (in some cases there may be no reason not to) then supposedly about 90% of these weapons have been destroyed by now.  The composition of some of these poisonous gases has been public knowledge for a very long time now however.  The need for vigilant toxic gas screening by chromatography, seems unlikely disappear in this complicated modern age.




7 thoughts on “sniffers, puffers and trace-detection

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