Measuring alcohol in the body

Evidential breath-alcohol analysis with the Alcotest® 7110 and Alcotest® 7110 Evidential

Alcoholand society

In many countries around theworld, the results of breath-alcoholanalysis are already admissable asevidence in court. As laws change,other countries are also going thesame way. Due to technologicaladvances, today's instruments arehighly accurate in measurement,simple in operation and virtuallytamper-proof.

Alcohol, loved by some and cursedby others, is appreciated by mostpeople as a means of stimulation andrelaxation. We all know that consump-tion of alcohol has a negative impacton our perception and impairs ourperformance.

However, this change in state doesnot necessarily need to be unplea-sant, and it is not without reason thatalcohol plays an important part insocial situations in some countries.Alcohol stimulates, inspires, liberatesand exhilarates. It removes inhibitionsand makes establishing contacteasier. Alcohol is missing at no cele-bration, at no reception, at no ban-quet. Alcohol is a firm fixture of oureveryday life, and has been for manycenturies.

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Over the centuries, however, therequirements placed upon us in oursocial lives have changed considerab-ly. Today we live in a modern world inwhich speed and technology defineour daily life. Alcohol can be pleasantand fun, but the consumption of alco-hol also holds many dangers.

One draught above heat

makes him a fool, the second mads him and

a third drowns him !Shakespeare

(from "Twelfth Night")

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Accidents under the influence of alcohol

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Alcohol on our roadsWhen a person's consciousness isclouded by alcohol, this exposes usto many risks. Nowadays, we oftenencounter situations which demandour concentration and swift reactions.Who can tell how much alcohol is inhis or her blood after two glasses ofwine?

Only our conscience can help usdecide how much "too much" is, yet itis precisely our conscience whichbecomes increasingly unable to func-tion with each sip of alcohol.

In Germany, for example, more than60,000 road accidents involving peo-ple under the influence of alcoholwere recorded per year. The proporti-on of people killed and seriously inju-red in these accidents was particular-ly high, and for more than 1,000 peo-ple the accident was fatal. Everysingle accident which occurs due toexcessive consumption of alcohol isone accident too many!

Such accidents show us where thelimits are, making it clear what the dif-ference between moderate andexcessive can mean. Our sense ofresponsibility towards ourselves andothers decides how we answer thequestion "alcohol, yes or no?".

We all have a duty to accept this res-ponsibility to prevent risk situationsand dangers from occurring in thefirst place. However, only accurate,unmistakable proof of alcohol canshow where the limits are, and thisaccurate proof can be obtained onlyby means of technical apparatus.

19981999

20002001

64,368,1

69,971,3

Number of traffic accidents in Germany under the influence of alcohol (in thousands)

Slightly injured persons 64 %

Fatalities 3 %

Severely injured persons 33 %

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Alcohol screening test When determining a person'sbreath-alcohol concentration, adistinction is made between a preli-minary screening test and an evi-dential analysis. A screening test isused by the police officer at theroadside to help decide objectivelywhether, if a particular limit isexceeded, an evidential breath-alcohol analysis needs to becarried out afterwards orwhether a blood samplewill be taken.

Alcohol screeningtests are performedusing Alcotest tubes, in whichchemicals are discoloured by thealcohol in the breath, or using theelectronic Alcotest 7410 hand-heldinstruments.

The familiar Alcotest tube with thesample bag is probably the oldestmethod of obtaining proof of alcoholin a screening test. An anecdotalaccount of how this breath-alcoholtest was invented at the beginning ofthe 1950s goes like this: in the mor-ning after a party, the chemists atDräger's test tube department eachaccused the next of smelling mostintensively of alcohol. To clarify thematter for once and for all, an objec-tive and accurate method of measure-ment had to be found, which is howthe breath-alcohol test tube came intoexistence.

However, require-ments with regard toaccuracy, speed, testfrequency and effec-tive and economicuse rose considerab-ly over the years. Ascreening test mustbe able to be perfor-med swiftly and supp-ly accurate results,and today mainlyelectronic devicesare used.

Although in recent years the number of

traffic accidentsunder the influence

of alcohol has been falling constantly,

it is stillalarmingly high !

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The physiologyof alcohol

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After drinking, the alcohol, or to giveit its more accurate chemical name,ethyl alcohol or ethanol, is taken upby the blood in the gastro-intestinaltract and transported, via the heartand the lung, to the arteries of thebrain. From the heart the blood is cir-culated around the rest of the body,into the arteries of the arms for exam-ple. From there it is distributedthroughout the tissue and, finally,flows back through the veins.

Effects on reaction speed Once alcohol reaches the arteries ofthe brain, it affects our speed of reac-tion and, in sufficient quantities,instantly causes unusual, alcohol-rela-ted behaviour. The extent to which thespeed of reaction is affected determi-nes whether a person can still safelydrive a car or whether there is anincreased risk of accident.

To judge whether or not a person isfit to drive would require a method ofdirectly measuring this reduction inreaction speed at the roadside, butas yet this is too expensive to be aviable option.

To obtain nevertheless a useable pro-cedure, "auxiliary variables" are usedwhich permit an indirect conclusionto be drawn about a person's speedof reaction: a sample of air from thelungs or a sample of venous bloodfrom the inside of the elbow is takenand its alcohol concentration determi-ned.

Measurement using air from the lungs (breath-alcohol concentration BrAC)

Measurement using venous blood (blood-alcohol concentration BAC)

Diagram of alcohol distribution in the body

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Henry‘s lawThe alcohol concentration is measu-red using air from the lungs orvenous blood.

In accordance with Henry's law, diffu-sion processes, which are also whatcauses oxygen to be taken up in thelungs, achieve a balance between thealcohol concentration in the blood inthe lungs and the alcohol concentrati-on in the air in the lungs. The breath-alcohol measurement involves directlydetermining this concentration.

From the heart, the blood is circula-ted around the rest of the body, intothe arteries of the arms for example.

From there the blood is distributedthroughout the tissue and, finally,flows back through the veins. A sam-ple of this venous blood is taken fromthe inside of the elbow and used todetermine the blood alcohol concen-tration indirectly by means of a furthermultistage procedure.

Alcohol in the arteries of the brain

Physiological degree of alcoholization

Alcohol-related odd driving behaviour

Variable for reduced speed of reaction

No direct measurement available for road traffic use

Only measurement of auxiliary variables possible

Collection of a breath sampleof air from the lung

Sample of venous bloodfrom the inside of the elbow

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Measurement methods in comparison

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Evidential measurementAfter a positive screening test an evi-dential alcohol analysis must be per-formed. Lawmakers in different coun-tries have set appropriate limit valuesfor the two procedures, i.e. breathand blood alcohol analysis.

The breath-alcohol concentration(BrAC), a gas concentration, isexpressed for example in milligram-mes of ethanol per litre of exhaled air(mg/l). The blood alcohol concentrati-on (BAC), a liquid concentration, isexpressed for example in per mille (‰)and refers to the amount of ethanol ingrammes in each litre of blood.

In many countries the lowest limitvalue which constitutes an offence isa blood alcohol concentration of 0.5per mille (‰), the corresponding limitfor breath-alcohol concentrationbeing 0.25 milligrammes per litre(mg/l) of exhaled air.

Breath-alcohol concentration – a more accurate measureEven though the limit values for bothprocedures may be equivalent from alegal viewpoint, the breath-alcoholconcentration nevertheless offers amore direct measure of actual impair-ment of driving ability.

This is because of the path that alco-hol takes through the body. From theplace where the breath sample istaken from the lung, the blood trans-ports the alcohol via the heart to thearteries of the brain, where the rapidincrease in alcohol concentrationimpairs speed of reaction. Before theblood sample can be collected fromthe venous blood inside the elbow,however, the blood containing thealcohol is first distributed in tissuethroughout the body.

A further advantage of the breath-alcohol analysis is that the alcoholcontent can be determined directlyand documented immediately, evenon site, for instance at the roadside.

Blood alcohol analysis – a laborious process Blood alcohol analysis first requires adoctor to take a sample of venousblood from the inside of the elbow –this may even involve a trip to thenearest hospital. The blood sample isthen submitted to a forensic labora-tory for analysis. The blood must firstbe prepared by separating its solidconstituents and then analysed.Finally, once the concentration in theobtained blood serum has beendetermined, the alcohol concentrati-on in the whole blood can be calcula-ted, indirectly, using a mean value.

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Breath-alcohol concentration - a more

accurate measure !Comparison with limit value

Calculation of whole blood concentration (‰) based on blood

serum using mean divisor 1.2

Determination of alcohol concentration (‰)

in blood serum (liquid concentration)

Blood serum

Separation of the solid constituents

Transport

Sampling of venous whole blood

Veins of the arms

Arteries of the armsArteries

of the brain

Capillary blood in the alveoli

Blood / heart

Alcohol in the gastro-intestinal tract

Heart Lung air (Henry's law)

Direct comparison with limit value

Collection of a breath sample of lung air

In each case direct determination of alcohol concentration (mg/l)

in lung air (gas concentration)

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SERIAL NO. :

ARGA001

SAMPLE NO.:

11

CALIBR. NO.:

65287

*************************

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0 1 2 3 4 5 6 7 8 9

PROTOCOL NO:

0007

DATE:

07 / 12 / 98

START:

23 :03 W

END :

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Alcotest 7110

10

Following the introduction of thelegal framework, the Dräger Alcotest7110 and the Dräger Alcotest 7110Evidential, devices capable of satisfy-ing the strict requirements for eviden-tial breath-alcohol analysis in manycountries, were developed.Sophisticated technology preventsincorrect measurement results to thedisadvantage of the car driver concer-ned (e.g. in the case of mouth alco-hol), detects any attempt to manipula-te the measurement and, in suchcases, immediately aborts the measu-rement and states the reasons for theaborted measurement.

Reliability with two individual mea-surements The Dräger Alcotest 7110 Evidentialalways requests two individual mea-surements, each with a separatebreath sample. The second breathsample is to be delivered by the sub-ject two to five minutes after the firstbreath sample. Only if both individualresults are successful and the resultscorrespond within very close limits isthe valid final result printed in a proto-col by a printer. Once the breathingair enters the instrument for analysis,different parameters are determinedsimultaneously by two mutually inde-pendent sensors: the breath tempera-ture, exhalation flow rate, the blowingvolume and the breath-alcohol con-centration.

Reliability with two separate mea-suring systems The Dräger Alcotest 7110 Evidentialdetermines the breath-alcohol con-centration using two different measu-ring systems: an infrared sensor andan electrochemical sensor. Both mea-suring systems use their respectivesensors to independently measurethe alcohol concentration in air exha-led deeply from the lungs, and assuch each system monitors the other.The measurement is only accepted ifthe results provided by both sensorscorrespond to within very narrowlimits.

By using two measuring systems withdifferent analytical specificity, thedevice is able to reliably detect anyinterfering substances which may bepresent in the exhaled air and whichmight influence the result in any way,such as petrol or paint vapours, ace-tone or solvent vapours.

Cross-sectional diagram of theDräger Alcotest 7110. The breath hose, two sensorsystems, electronics, display and internal printer can be seen.

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Side of the detector

Flow sensor

Infrared optical sensor with electrochemical sensor and flow sensor

Electrochemical sensor with sampling unit

Side of the light source

Light source

Gas

DetectorInterference filter

Window Window

Diagram showing the measurement in the infrared optical sensor

Spectrallines

Infrared spectrum

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The infrared measuring systemA light source in the infrared opticalsensor emits light at different wave-lengths (colours) in the infraredrange of the spectrum (i.e. not visibleto the human eye). In the schematicdiagram, the colours of visible lightare used rather than the invisibleinfrared spectrum. The light passesthrough two windows and an interfe-rence filter which only allows penetra-tion of certain wavelengths (thegreen light in the diagram). A detec-tor measures the intensity of the inco-ming light and transmits a correspon-ding signal to the device's electronicssystem. If a gas (ethanol, for example)which absorbs part of the light at aparticular wavelength (the green lightin the diagram) is present betweenthe two windows, the light intensitymeasured by the detector will drop,as will its electrical output signal.

The higher the alcohol concentrationand the longer the path travelled bythe light through the gas, the morethe signal will be reduced, which isthus a measure for the alcohol con-centration.

Alcotest 7110

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The electrochemical measuringsystemIn the electrochemical measuringsystem, which is also used in a simi-lar manner in the screening instru-ment Alcotest 7410, a piston drivenby an electric motor conveys a sam-ple of air with an exact volume into asampling chamber. Here the electro-chemical DrägerSensor selectivelyand highly accurately analyses thebreath sample for the presence ofethanol. The alcohol to be analysedwill be electrochemically oxidized onthe catalyst layer of the measurementelectrode. The electrons released bythe reaction at the electrode cause acurrent to pass through the connec-tion wires to the device's electronics.This current depends on the alcoholcontent in the sample chamber.

Piston

Electrochemical Sensor

Electric pump motor

Sampling chamber

Cross-sectional diagram of the electrochemical sensor

Development of the sensor current ofthe electrochemical sensor over timeduring analysis of a sample of breathcontaining approx. 0.5 mg/l ethanol

Electrochemical measuring system

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Pump drawsin sample

Sen

sor

curr

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μA]

Time [s]

10 20 30 4000

400

500

300

200

100

Pump drawsin sample

Connection wiresMeasurement electrode

with catalyst layer on both sides

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68XXXXX06 95 ARJF-0033

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Breath volumeThe volume of air which the test sub-ject blows into the instrument is mea-sured using one or two different flowsensors to ensure that the requiredminimum volume of breath - which insome countries depends on the ageand sex of the test subject - is rea-ched. This ensures that only deeplung air is analysed. Only deep lungair shows a clear correlation betweenthe alcohol concentration in the airand that in the capillary blood in thealveoli. If the breath sample does notreach the required levels with regardto volume and flow rate, the instru-ment aborts the measurement.

Minimum breath volume required in Germany [litres]

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WomenMen

Age groups [in years]

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Alcotest 7110Evidential

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Breath temperatureLike all other components of theinstrument which come into contactwith the test subject's exhaled air, theDräger Alcotest 7110 breath hoseand the handle of the breath hoseare heated to prevent any condensati-on of the breathing air.

At the mouthpiece end of the breathhose of the Alcotest 7110 Evidentialtwo additional temperature sensors,which project into the mouthpiece,record the temperature of the exha-led air flow. The alcohol concentrati-on in the exhaled air (BrAC) increa-ses as the body temperature andexhalation air temperature rise, due tothe fact that an increased body tem-perature causes more alcohol in thelungs to evaporate out of the arterialblood in the lungs into the lung air.This takes place in accordance with afixed physical principle known asHenry's law. Furthermore, as thebody temperature rises, the exhalati-on air in the upper airways loses lessof its alcohol concentration. Whencalculating the measurement result,therefore, the two breath temperaturesensors in the breath hose are usedto always relate the breath-alcoholconcentration to a fixed exhalationtemperature of 34°C, ensuring thatpersons with for example a higherthan normal body temperature are notdisadvantaged by a higher measure-ment result.

Ways to breathe Hyperventilation and hypoventilationHow the test subject breathes direct-ly before giving the breath sample,and the ambient temperature, alsohave an influence on the measure-ment of the breath-alcohol concentra-tion at the end of the exhalation. Forinstance, if the test subject hyperven-tilates (breathes excessively) or ifambient temperatures are low, thearea of the mouth and throat and thewindpipe are cooled to below normallevels. This causes the temperatureof the exhaled air to fall and, conse-quently, the uncorrected breath-alco-hol concentration is lower.

Likewise, hypoventilation (shallowbreathing) or high ambient temperatu-res can increase the temperature ofthe breath and thus result in a higheruncorrected breath-alcohol concen-tration. If on the other hand the actualmeasured breath temperature is usedto correct the final result and relate itto an exhalation temperature of 34°C,the way the test subject breathes andthe ambient temperature will notaffect the result of the measurement(Source of diagrams: Prof. Slemeyer,University of Applied SciencesGiessen-Friedberg, Germany).

without temperature correction

with temperature correction

How different ways of breathingaffect breath-alcohol concentration(BrAC)

Breath temperature sensors

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BrA

C [m

g/l]

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0,25

0,2

0,15

0,05

Expiration time [s]

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HypoNormalHyper

BrA

C [m

g/l]

Expiration time [s]

HypoNormalHyper

0

0,1

0,25

0,2

0,15

0,05

0 3 6 9 12 15

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Mouth alcoholIf shortly before the breath sample istaken the test subject consumes asubstance containing alcohol(liqueur-filled chocolates, for example,or an alcohol containing mouthspray),the exhaled air absorbs alcohol notonly from the lungs, but also fromthese substances in the upper part ofthe mouth and throat. As a result, thealcohol concentration detected in theexhaled air will be higher than theconcentration in the lung air.However, within a few minutes thiseffect is completely cancelled out asthe remaining alcohol in the mouth istaken up by the saliva or absorbedinto the body. Waiting for at least 10minutes before the measurement isperformed and comparing the resultsof two individual measurements atintervals of several minutes excludesthe possibility of residual alcohol inthe mouth influencing the final result.(Source of the diagram: Prof.Slemeyer, University of Applied

Sciences Giessen-Friedberg,Germany).

Reliability of the measurement results For all measurements of alcohol con-centration, breath temperature andbreath volume, the Dräger Alcotest7110 Evidential - as used for examplein Germany - uses two mutually inde-pendent measuring systems whichmonitor one other. The results of thetwo individual measurements produ-ced by these individual measuringsystems, carried out at an interval ofseveral minutes, must correspond towithin very narrow limits. This doublesensor technology, together with thetwo individual measurements, ensu-res the high reliability of the measure-ment results.

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Cherry liqueur chocolateMouth sprayBrandy chocolate

0

The technology in the new evidential instruments

prevents falsemeasurements !

Heated breath hose of the Alcotest 7110 Evidential

Decrease in alcohol concentrati-on over time following consump-tion of alcoholic substances

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Traffic lawsNational regulations stipulatingappropriate limit values for breath-alcohol concentration, for example0.25 mg/l, establish the legal basisfor the application of the breath-alco-hol analysis. If these limit values areviolated an appropriate fine will beimposed and the driver may be ban-ned from driving for a limited period.

Type approvals The Dräger Alcotest 7110 and theDräger Alcotest 7110 Evidential satis-fy the requirements of different natio-nal and international standards andregulations, for example the DIN VDE0405 and the OIML R 126. Theyhave been approved respectively bydifferent national authorities such asthe Physikalisch-TechnischeBundesanstalt (PTB), the LaboratoireNational d’Essais (LNE) and theNederlands Meetinstituut (NMi), follo-wing an extensive series of tests. Inmany countries they can therefore beused for evidential breath-alcoholconcentration measurement for official monitoring of road traffic.

Legal bases

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VerificationAbove and beyond the technicalrequirements and type approval,every single instrument is regularlyverified in many countries by an offici-al verification authority or indepen-dent institution, in accordance withnational metrology and verificationlaws and respective regulations. Theresults are related to nationalstatutory metrology standardsby using for instance theDräger Alcocal. During theverification process theerror limits specified forthese instruments mustbe adhered to. Thisprocedure constitu-

tes an additional quality assurancemeasure which neither manufacturernor operator can influence.

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Approval andverification

as measures of quality control !

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Interlock

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Withdrawal of driving licenceThe result of a measurement conduc-ted by an evidential breath-alcoholanalyser may lead to a person's dri-ving licence being withdrawn. Thissuspension is regarded not as a pen-alty but rather as a road safety mea-sure. However, many of the offenderswho depend on their car for workregard the revocation of their licenceas a severe punishment. Losing one’sdriving licence can be life-shattering.Social isolation or the resulting lossof one's job can lead to intensifiedalcohol abuse.

The aim of licence suspension is notto prevent a person driving a car ingeneral, but to prevent driving whileunder the influence of alcohol and toencourage a change in drinkingbehaviour. This may be achieved byinstalling an interlock to the ignitionsystems of the vehicle. The drivermust blow into the mouthpiece of thehandset – only if the breath-alcoholconcentration is below a pre-determi-ned value will it be possible to startthe engine.

Measurement technologyThe Dräger Interlock measures thedriver's breath-alcohol concentrationusing the same type of electrochemi-cal measuring system as the scree-ning instrument Alcotest 7410 andthe evidential instrument Alcotest7110. Special software prevents tam-pering and circumvention of thesystem. All events, such as delivery ofor refusal to provide a breath sample,motor starts and stops, date and timeas well as the breath-alcohol concen-tration are recorded by a data logger.

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Dräger Interlock -a road safety measureAn alcohol ignition interlock is an aidfor a driver whose driving licence hasbeen suspended. The use of this aiddoes not eliminate the impairment,but ensures safe driving of thevehicle. A person with defective visi-on must wear eyeglasses when dri-ving, and an alcoholic should use aninterlock before being allowed tostart a car. The interlock is designedto modify behaviour patterns, to edu-cate and to prevent irresponsibleoperation of motor vehicles, trucks,machinery or equipment when theoperator is under the influence ofalcohol.

The interlock can also be used byparents to make sure that their child-ren do not drink and drive. It allowspeople to learn new behavioural pat-terns with regard to drinking and dri-ving.

The interlock helps in the rehabilitati-on process while promoting roadsafety.

Interlock

a safe start !

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DrägerServiceDräger equipment must alwaysbe fully operational and safe.DrägerService offers a regularinspection service and isquicklyavailable in the event of mal-function. Your equipment willbe repaired and back in opera-tion as quickly as possible.DrägerService facilitates the vitalflow of information betweenclient and manufacturer.

Dräger WorldwideThe Dräger sales and serviceorganisation is spread through-out the world. It comprises morethan 25 subsidiaries and associ-ated companies to ensure thatDräger is always within easyreach of its clients and in closecontact with all importantmarkets. Dräger's ever increas-ing market share demonstratesthe company's internationalcompetitiveness and strength.

Dräger Safety AG & Co. KGaARevalstrasse 1D-23560 LuebeckGermanyTel. +49 451 882 - 0Fax +49 451 882 - 20 80www.draeger-safety.com

Dräger ExpertiseSince 1889, Dräger has had an outstanding reputationfor solving problems in the field of human breathing.Dräger has been deeply involved in the handling ofgases, in particular hazard protection and the savingof life in medical and industrial emergencies.Many of the company's 9.800 employees are active inresearch and innovation to ensure that the latesttechniques and scientific advances are fully testedbefore their inclusion in new equipment.

Dräger has subsidiaries in the following countries:Australia, Austria, Belgium, Bulgaria, Canada,China, Croatia, Czech Republic, Denmark, France,Great Britain, Hungary, Indonesia, Italy, Japan,the Netherlands, Norway, Romania, Singapore,South Korea, Slovenia, Slowakia, South Africa, Spain,Sweden, Switzerland, Thailand, Yugoslavia, USA.Additionally, Dräger is widely represented inCentral and South America, Africa, the Middle East,the Far East and Eastern Europe.

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Quality and Environmental ManagementOur mission includes the continuousimprovement of our Quality andEnvironmental Management Systemsin accordance with ISO 9001 andISO 14001.

Represented by: