1.
June 2004
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Draeger Safety
Entrada a espacios confinados

2.
June 2004
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Draeger Safety
Confined Spaces
 Que es un espacio confinado?
 American National Standards Institute (ANSI Z-117.1-1989)
– An enclosed area that has all the following characteristics: its primary
function is something other than human occupancy, has restricted entry
and exit, and may contain potential or known hazards
– Que su funcion primara se para otro uso y no para la ocupacion humana
que tenga entradas restringida como salidas y que puede tener conetener
sustancias potenciales riesgosas
 American Petroleum Institute
– Confined spaces are normally considered enclosures with known or
potential hazards and restricted means of entrance or exit
– Los espacios confinados normalmente se consideran los recintos con sabido o
peligros potenciales y medios restringidos de la entrada o de la salida
 OSHA (29 CFR 1910.146) General Industry
– A space that is large enough that an employee can bodily enter and
perform assigned work, has limited means for entry or exit, and is not
designed for continuous human occupancy
– Un espacio que es bastante grande que un empleado puede entrar en persona y
realice el trabajo asignado, ha limitado los medios para la entrada o la salida, y
no es diseñado para la ocupación humana continua

3.
June 2004
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Draeger Safety
Confined Spaces
 What is a confined space?
 OSHA (29 CFR 1915.4) Marine
– A compartment of small size and limited access such as a
double bottom tank, coffer dam, or other space which by its
size and confined nature can readily create or aggravate a
hazardous exposure (an enclosed space on the other hand is
any space other than a confined space which is enclosed by
bulkheads and overhead; it includes cargo holds, tanks,
quarters and machinery and boiler spaces.
– OSHA (29 CFR 1926.21) Construction
– Any space having limited means of egress, which is subject to
accumulation of toxic or flammable contaminants or has an
oxygen deficient atmospheres

4.
June 2004
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Draeger Safety
Confined Spaces
 What is a confined space?
 NIOSH
– A space which by design has limited openings for entry and
exit; unfavorable natural ventilation which could contain or
produce dangerous air contaminants, and which is not intended
for continuous human occupancy. NIOSH also classify confined
spaces:
– Class A spaces: those that present situations which are
immediately dangerous to life or health; includes deficient in
oxygen or contain flammable or toxic atmospheres
– Class B spaces: do not present an immediate threat to life or
health; however, they have the potential for causing injury or
illness if protective measures are not used
– Class C spaces: where any hazards posed are so insignificant
that no special work practices or procedures are required

5.
June 2004
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Draeger Safety
Confined Spaces
 OSHA also classifies confined spaces as permit-
required or non-permit required; a permit-required
confined space has one or more of the following
characteristics:
 contains, or has the potential to contain, a hazardous atmosphere
 contains a material that has the potential to engulf an entrant
 has an internal configuration such that an entrant could be
trapped or asphyxiated by inwardly converging walls or by a
floor that slopes downward and tapers to a smaller cross-section
 contains any other recognized serious safety or health hazard

6.
June 2004
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Draeger Safety
Simply put, a confined space is:
 Limited Access and/or Egress
 Able to be entered by humans
 Not designed for continuous human occupancy
 Real potential for life threatening
circumstances
Confined Spaces

7.
June 2004
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Draeger Safety
Confined Spaces
 Typical examples
Sewers
Underground
cable/electrical vaults
Water/storage
tanks
Aircraft wings during maintenance Process/mixing vessels Grain silos
Cargo holds
Construction and
excavation
Tunnels and pipes
Mobile tankers

8.
June 2004
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Draeger Safety
Confined Space Entry
What needs to be determined prior to entry, during
confinement and upon re-entry?
• Oxygen (19.5 to 23.5 % by vol.) 20.9% ambient
• Combustible Gas (Below 10% LEL)
• Toxic Gases (Known to be present)

9.
June 2004
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Draeger Safety
Dangers
• Oxygen - Too much or too little
• Toxic - Bodily Damage
• Combustible - Explosions

10.
June 2004
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Draeger Safety
What is Oxygen?
- Required to support life and support combustion
- 20.95% in ambient air
How is it Measured?
- Typically in % by volume scale
- Safe range from 19.5 to 23.5% by volume
Gas Detection Basics

11.
June 2004
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Draeger Safety
What is Toxic?
- Corrosive or poisonous or both
- Danger varies with each type of toxic in ambient air
How is it Measured?
- Typically in parts per million (ppm) scale
- Safe range determined by NIOSH for each gas
- Can be measured in Time Weighed Averages
(TWA). Typically 8 hour shifts.
- Can be measured in Short Term Exposure Level
(STEL). Typically 15 minutes
Gas Detection Basics

12.
June 2004
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Draeger Safety
What is a Combustible Gas?
- Explosive with ideal conditions
How is it Measured?
- Typically in % by vol. (%vol.) or
Lower Explosive Limit (LEL)
- Safe range determined by NIOSH for each gas
- Alarm warning set to 10 % LEL
Gas Detection Basics

13.
June 2004
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Draeger Safety
FIRE TRIANGLE
EXPLOSIVE
Fuel Oxygen
Spark / Ignition
Source

14.
June 2004
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Draeger Safety
Mixtures of Flammable Gases and Air
 It is a commonly held misconception that any
mixture of flammable gas and air is highly
dangerous and explosive. This is not the case
 For most flammable substances there is only a
relatively small range of gas-air mixtures which
are explosive (see below)

15.
June 2004
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Draeger Safety
Explosive Range, Some Examples
 Only the red ranges for the below substances are
explosive, the green regions will not sustain burning
and exhibit no danger of explosion!
Explosive Range
0% 20% 40% 60% 80% 100%
Pentane
Methane
Hydrogen
Acetone
% Vol. of Gas in Air

16.
June 2004
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Draeger Safety
The beginning of the red explosive
range is called the lower explosion limit (LEL)
Explosive Range
0% 5% 10% 15% 20% 25%
Pentane
Methane
Hydrogen
Acetone
% Vol. of Gas in Air
 Note that each of the substances listed below has a different LEL,
for example, methane’s LEL is 5% by volume and pentane’s is
1.4% by volume
Explosive Range
0% 20% 40% 60% 80% 100%
Pentane
Methane
Hydrogen
Acetone
% Vol. of Gas in Air

17.
June 2004
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Draeger Safety
The end of the red explosive
range is called the upper explosion limit (UEL)
Explosive Range
0% 5% 10% 15% 20% 25%
Pentane
Methane
Hydrogen
Acetone
% Vol. of Gas in Air
 Note that each of the substances listed below has a different UEL, for
example, methane’s is 15% by volume and pentane’s is 6.4% by volume
Explosive Range
0% 20% 40% 60% 80% 100%
Pentane
Methane
Hydrogen
Acetone
% Vol. of Gas in Air

18.
June 2004
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Draeger Safety
An Alternate Terminology for the
Red Explosive Range
 The explosive range of a gas is between the
LEL and the UEL of a gas
Explosive Range
0% 5% 10% 15% 20% 25%
Pentane
Methane
Hydrogen
Acetone
% Vol. of Gas in Air

19.
June 2004
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Draeger Safety
The % LEL Scale
 Since one normally references flammable-gas measurements to pure air, a
special set of units has been adopted called the %LEL scale
 This set of units is useful when the goal is to avoid explosive dangers by
staying under the LEL of the gas
 Pure air (without any flammable gas content) is assigned a value of 0%
LEL, the LEL of the gas is assigned a value of 100% LEL. Using
methane as an example, 5% by volume corresponds to 100 %LEL
Explosive Range
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15%
Methane
% Vol. of Gas in Air
0 – 100% LEL

20.
June 2004
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Draeger Safety
The %LEL Scale
 When working with the %LEL scale, you try to stay in the green
range, that is, between 0 and 100% LEL
 Over 100% LEL, there is a danger of explosion
 Remember, the % LEL scale corresponds to different absolute %
Vol. gas concentrations for different substances because the LEL of
each gas is different
Explosive Range
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15%
Methane
% Vol. of Gas in Air
0 – 100% LEL

21.
June 2004
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Draeger Safety
Lower Explosive Limit
 LEL is expressed as a percentage of the
volume needed to create combustion
Methane LEL = 5% methane by volume
0.5% methane by volume = 10% LEL
1.0% methane by volume = 20% LEL
2.5% methane by volume = 50% LEL
4.0% methane by volume = 80% LEL
+ =
5% CH4
= 100% LEL

22.
June 2004
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Draeger Safety
The %LEL Scale
 The LEL scale has the advantage that it focuses
on the explosion danger associated with the gas
 Under 100% LEL is safe
 Over 100% LEL is dangerous
 This is true regardless of the specific gas in
question

23.
June 2004
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Draeger Safety
FIRE TRIANGLE
EXPLOSIVE
Fuel Oxygen
Spark / Ignition
Source

24.
June 2004
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Draeger Safety
How can gases be detected?
With Draeger Safety Gas Detection Instrumentation
Using Draeger Safety Sensor and Glass Tube*
Technology
* Not discussed in this presentation

25.
June 2004
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Draeger Safety
DSensor Technology

26.
June 2004
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Draeger Safety
Sensor Technology
 Electrochemical Sensors (EC)
 Filter Media
 Catalytic Oxidation Sensors (Cat)
 Thermal Conductivity Sensors
 Infra-red Sensors (IR)
 CO2 & Ex Versions

27.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors

28.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 Based on a chemical reaction that
produces an electrical response/signal.
 The more gas that is present, the larger
the signal that is generated by the sensor.
 This signal is directly proportional to the
gas that is present.

29.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
1.) Gas to be Measured
2.) Dust & Mist Filter
3.) Diffusion Membrane
4.) Measuring Electrode
5.) Electrolyte
6.) Reference Electrode
7.) Counter Electrode

30.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 How are the sensors made specific to one particular
gas or vapor?
 Choice of Diffusion Membrane, Electrolyte,
Electrodes, and Bias Voltage
 Draeger’s patented Three-Electrode Technology
maximizes response to the gas of concern and
minimizes the response to other chemicals.
 Gases with similar elements, chemical properties,
or chemical bonds may produce similar reactions.
 Gases with opposite chemical properties may
produce a negative reaction.

31.
June 2004
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Draeger Safety
Display
Circuitry
Current
Potential
Control
Sensor
Gas
The sensor produces a current proportional to the gas concentration.
EC Sensor Principle Overview

32.
June 2004
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Draeger Safety
Filter Media
 Chemical Filters
 D3T for CO Sensor
 OV’s and H2S
 B2T for Odor Sensor
 H2S
 K1T for SO2 Sensor
 H2S

33.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 What is the expected life of a sensor?
 This varies with the type of sensor.
 The Draeger XS Sensors for CO, H2S & O2
have Three or Five-year Warranties, the
longest in the market.
 The XS stands for “eXtra Stability”, this
design allows the sensor to operate longer
and more stable over it’s life.
 Life is NOT determined by exposure to gas,
but is more dependant on time.

34.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 How does Temperature effect the sensor?
 In general; these chemical reactions occur
quicker and stronger at higher temperatures and
slower and weaker at lower temperatures.
 A temperature compensation circuit inside the
sensor accurately compensates for changes in
ambient temperature.
 This internal compensation is better than PCB
mounted compensation, a feature exclusive to
Draeger-Sensors®

35.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 Does Pressure make any difference on the
measurement by the sensor
 Higher ambient pressures will “force”
more gas into the sensor and thus
produce higher readings.
 The Draeger XS sensor have a pressure
compensation port which minimizes the
effects of pressure.

36.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 Does Humidity effect the Sensor?
 Humidity by itself has minimal effect on
the sensor reading.
 However, should condensation occur, and
a layer of water covers the sensor, this will
prevent the gas from entering the sensor.

37.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 Can Dust and other Particulate matter make a
difference?
 Should enough dust cover the sensor
inlet, it could slow down or block gas from
entering the sensor.

38.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 What exactly is a “Smart” Sensor?
 Typically this means that when plugged
into a monitor, the instrument recognizes
what the sensor is designed to measure.

39.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 What is special about the Draeger-Sensor?
 The XS,R and PS2 Sensors contain much
more data; Gas ID, Calibration Data,
Operating Parameters, Temperature
Compensation, Measuring Ranges, Alarm
Values, etc.
 This information stays with the sensor when
installed in another instrument.
 Transportable Calibration !!!

40.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors
 How often do you need to calibrate the
Draeger XS Sensors?
 Per our specifications the CO, H2S and
O2, XS Sensors only require calibration
every 12 months (once a year)!
 Other XS Sensors, once every six months.

41.
June 2004
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Draeger Safety
Draeger-Sensor® Advantages
 Three or Five-year Warranty on CO, H2S, O2!!!
 The XS O2 sensor is NOT based on a
consumptive reaction.
 Interchangeable with other Draeger
Portables.
 Transportable Calibration Data.
 Long periods (up to 1 year) between routine
required calibrations.
 Widest variety of gases and vapors detected.

42.
June 2004
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Draeger Safety
• Oxygen
• Carbon Monoxide
• Hydrogen Sulfide
• Hydrogen Sulfide 1000
• Sulfur Dioxide
• Organic Vapors
• Organic Vapors - A
• Hydrides
• Hydrogen Peroxide
• Nitrogen Dioxide
• Nitric Oxide
• Phosphine 1000
• Hydrogen Cyanide
Available DrägerSensors XS EC
• Mercaptans
• Chlorine
• Carbon Dioxide
• Amines
• Hydrogen
• Hydrazine
• HF/HCl

43.
June 2004
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Draeger Safety
Electrochemical (EC) Sensors

44.
June 2004
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Draeger Safety
Catalytic Oxidation (Cat) Sensors

45.
June 2004
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Draeger Safety
Explosive Gas Measurement
Lean Explosive Rich
0-100 % LEL Explosive UEL Range
> 100%LEL

46.
June 2004
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Draeger Safety
Catalytic Oxidation (Cat) Sensors
 Metal Sinter Disk
 Compensating
Element
 Detection Element
 Wheatstone Bridge

47.
June 2004
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Draeger Safety
Lower Explosion Limits
Example: Methane 100% LEL = 5% Volume
Pellistor
Signal
Level
UEL
LEL
Gas concentration too
low to sustain flame
Explosive
region
Oxygen concentration too
low to sustain flame
Concentration of hazardous gas ( % Volume)
Possible source of danger: Same readings for two different concentrations ( A & B)
A B
0
Catalytic
Thermal

48.
June 2004
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Draeger Safety
Catalytic Oxidation (Cat) Sensors
 A catalyst facilitates the reaction between oxygen
in the air and combustible substances.
 This oxidation reaction produces heat.
 The heat of this reaction increases the resistance
of the element in the catalytic bead.
 The increase in resistance changes the flow of
electric current in the electrical bridge.
 More gas, causes more heat, causes a large
deflection of signal which is displayed as an
increase %LEL signal.

49.
June 2004
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Draeger Safety
Catalytic Oxidation (Cat) Sensors
 A compensation element negates
variations in temperature and humidity.
 Sensor reacts to any gas that is readily
oxidized by the catalyst.
 Methane, Propane, Gasoline, NH3, CO, etc.
 Sensitivity to any gas is dependant on the
chemical bonds within the substance.

50.
June 2004
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Draeger Safety
Catalytic Oxidation (Cat) Sensors
 In general, the heavier the compound, the lower the response
the catalytic sensor.
 CH4, C3H8, C5H12, etc.
 Relative Sensitivities of Common Compounds*
 **** Referenced to Methane Calibration ****
 Methane, CH4 100%
 Propane, C3H8 70%
 Pentane, C5H10 50%
 Gasoline, CxHy 55%
 Benzene, C6H6 33%
 Hydrogen, H2 100 %

51.
June 2004
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Draeger Safety
Catalytic Oxidation (Cat) Sensors
 Poisoning Compounds
 Sulfur-bearing compounds (H2S, SO2, etc.)
 Halogenated (CL2, F2, etc.) Hydrocarbons
 Inhibiting Agents
 Heavy-Metals Containing Compounds
– Leaded Gasoline (Pb)
 Silicone-bearing (Si) Compounds
 Long-Chained Polymers
 High Concentrations of Combustible Gases

52.
June 2004
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Draeger Safety
Draeger-Sensor® Advantages
 Poison Resistant Design
 Measures Heavier Hydrocarbons.
 Measures many compounds in ppm.
 Unambiguous Measurement of LEL
 With Thermal Conductivity Element

53.
June 2004
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Draeger Safety
Thermal Conductivity (TC) Sensor
Ambiguous Ex Sensor Operation
 As more combustible gas is present in the
ambient atmosphere, it displaces the
available oxygen needed to carry out the
catalytic oxidization reaction.
 Less oxygen to carry out the catalytic reaction
causes the sensor signal to drop.
 There will be a point at which the sensor will
produce the same signal for concentrations
over the LEL as under the LEL.

54.
June 2004
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Draeger Safety
Thermal Conductivity (TC) Sensor
0% LEL
Lean Explosive Rich
100%LEL
0 Vol. % 5 Vol. % 15 Vol. %
Sensor signal decrease due to lack of O2
thermal conductivity
catalytic oxidation

55.
June 2004
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Draeger Safety
Thermal Conductivity (TC) Sensor
 Different compounds have different thermal
conductivity (heat of transport) and will carry
away more heat from a heated source.
 Increased concentrations of methane (or
other combustibles) will conduct more heat
away from the thermal conductivity element in
the catalytic sensor. (vs. air).
 The Draeger Ex Sensor (thermal) prevents
ambiguous measurement and can accurately
measure CH4 up to 100 %Vol.

56.
June 2004
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Draeger Safety
Infrared (IR) Sensors

57.
June 2004
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Draeger Safety
Infrared (IR) Sensors
 Various compounds absorb infrared
energy.
 They absorb different wavelengths of IR
light energy in different degrees.
 Higher concentrations of gas will absorb
more IR light energy.

58.
June 2004
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Draeger Safety
Infrared (IR) Sensors
 1.) IR Light Source
 2.) Lens
 3.) Cuvette / Chamber
 4.) Mirror
 5.) Lens
 6.) Beam Splitter
 7.) Light Filter
 8.) Measure Detector
 9.) Light Filter
 10.) Comp. Detector

59.
June 2004
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Draeger Safety
Infrared (IR) Sensors
 Gas is pumped, or diffuses into a chamber
with an IR light source.
 The targeted gas(es) absorb the IR energy.
 The detector on the other side of the
chamber measures how much light is
absorbed by the targeted compound(s).
 A compensation detector corrects for
blockage by dust, water and other
physical factors.

60.
June 2004
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Draeger Safety
IR-Ex versus Cat-Ex
 Operates in environments with Low or No
Oxygen concentrations
 Completely Immune to Poisoning and
Inhibiting Compounds that affect Cat-Ex.
 Measures %LEL, ppm, and %Volume
Concentrations of various gases.
 Different responses to different
compounds vs catalytic sensor
(specifying).

61.
June 2004
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Draeger Safety
Draeger-Sensor ® Advantages
 Available for Ex or CO2.
 Can be coupled with a Cat-Ex.
 Qualified for more than Methane
 Does not require a Pump for operation.
 Compensation detector.
 Not affected by temperature, dirt, or
vibrations.
 Easily cleaned measurement chamber

62.
June 2004
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Draeger Safety
Questions?
Thank you.