RKI Instruments GasWatch 2 User manual

www.rkiinstruments.com
GasWatch 2
Operator’s Manual
Part Number: 71-0065RK
Revision: F
Released: 2/2/11

GasWatch 2 Operator’s Manual
WARNING
Read and understand this instruction manual
before operating instrument. Improper use of the
gas monitor could result in bodily harm or death.
Periodic calibration and maintenance of the gas
monitor is essential for proper operation and cor-
rect readings. Please calibrate and maintain this
instrument regularly! Frequency of calibration
depends upon the type of use you have and the
sensor types. Typical calibration frequencies for
most applications are between 1 and 3 months,
but can be required more often or less often
based on your usage.

GasWatch 2 Operator’s Manual Warranty
Warranty RKI Instruments, Inc. warrants the GasWatch 2 sold by us to be free from
defects in materials, workmanship, and performance for a period of two
years from the date of shipment from RKI Instruments, Inc. This includes
the instrument and the original sensors. Replacement parts are warranted
for 1 year from the date of their shipment from RKI Instruments, Inc. Any
parts found defective within their warranty period will be repaired or
replaced, at our option, free of charge. This warranty does not apply to
those items which by their nature are subject to deterioration or
consumption in normal service, and which must be cleaned, repaired, or
replaced on a routine basis. Examples of such items are:
Warranty is voided by abuse including mechanical damage, alteration,
rough handling, or repair procedures not in accordance with the instruction
manual. This warranty indicates the full extent of our liability, and we are
not responsible for removal or replacement costs, local repair costs,
transportation costs, or contingent expenses incurred without our prior
approval.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ANY AND ALL OTHER WARRANTIES
AND REPRESENTATIONS, EXPRESSED OR IMPLIED, AND ALL OTHER OBLIGATIONS
OR LIABILITIES ON THE PART OF RKI INSTRUMENTS, INC. INCLUDING BUT NOT
LIMITED TO THE WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. INNO EVENT SHALL RKI INSTRUMENTS, INC. BE LIABLE
FOR INDIRECT, INCIDENTAL, OR CONSEQUENTIAL LOSS OR DAMAGE OF ANY KIND
CONNECTED WITH THE USE OF ITS PRODUCTS OR FAILURE OF ITS PRODUCTS TO
FUNCTION OR OPERATE PROPERLY.
This warranty covers instruments and parts sold to users only by
authorized distributors, dealers, and representatives as appointed by RKI
Instruments, Inc.
We do not assume indemnification for any accident or damage caused by
the operation of this gas monitor and our warranty is limited to replacement
of parts or our complete goods.
Absorbent cartridges
Filter elements, disks, or sheets
Pump diaphragms and valves

Table of Contents GasWatch 2 Operator’s Manual
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Wristband . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Sensor Cap/.Sensor Cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Charcoal Filter Disk in GW-2C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
LCD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Control Buttons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Printed Circuit Boards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Alarm Lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Buzzer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Vibrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Lithium Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Start Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Start-up Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Performing a Fresh Air Adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Turning Off the GasWatch 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Measuring Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Displaying the Peak, STEL, & TWA (GW-2C & GW-2H) . . . . . . . . . . . . . . . . . . 11
Displaying Min and Max (GW-2X). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Displaying and Setting the Alarm Points. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Setting the Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Setting the Fresh Air Reading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Setting the Span (Zero for GW-2X). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

GasWatch 2 Operator’s Manual Table of Contents
Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Replacing the Lithium Battery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Replacing the Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Replacing the Sensor Cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Replacing the Charcoal Filter Disk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Replacing the Wristband. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Appendix A: MRI Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
WARNING: Understand manual before operating. Substitution of
components may impair intrinsic safety. To prevent
ignition of a hazardous atmosphere, batteries must only
be changed in an area known to be nonhazardous. Not
tested in oxygen enriched atmospheres (above 21%).

1 • Introduction GasWatch 2 Operator’s Manual
Introduction
Using an advanced microprocessor controlled detection system, the
GasWatch 2 Personal Single-Gas Monitor detects the presence of either
carbon monoxide (CO), hydrogen sulfide (H2S), or oxygen (O2). The
GasWatch 2’s compact size and easy-to-use design makes it ideally suited
for a wide range of applications, including sewage treatment plants,
tunnels, hazardous waste sites, petrochemical facilities, oil fields, mines,
and chemical plants. The GasWatch 2 is even small enough to be worn
comfortably on the wrist like a watch. The GasWatch 2 offers a full range of
features, including:
• Hands free gas monitoring
• Compact “watch type” design
• Fast, accurate response with digital liquid crystal display (LCD)
• Visual, audible, and vibration alarms
• Microprocessor control for reliability, ease of use, and advanced
capabilities
• Peak, STEL, and TWA indication for GW-2C & GW-2H
• Minimum and maximum indication for GW-2X
• STEL, TWA, and over range alarms
• Sensor fail alarm
• Displays current time
• Over 3,000 hours of operation from 1 battery
• CSA classified for Class I, Division I, Groups A, B, C, and D hazardous
atmospheres
WARNING: The GasWatch 2 detects carbon monoxide, hydrogen
sulfide, or oxygen deficiency and elevated levels of
oxygen, all of which can be dangerous or life threatening.
When using the GasWatch 2, you must follow the
instructions and warnings in this manual to assure
proper and safe operation of the unit and to minimize the
risk of personal injury. Be sure to maintain and calibrate
the GasWatch 2 as described in this manual.

GasWatch 2 Operator’s Manual Specifications • 2
Specifications
Table 1: GasWatch 2 Specifications
GW-2C GW-2H GW-2X
Target Gas Carbon Monoxide
(CO) Hydrogen Sulfide (H2S) Oxygen (O2)
Detection Range 0 to 500 ppm 0 to 100.0 ppm 0 to 40.0% vol.
Display Increment 1 ppm 0.5 ppm 0.1% vol.
Detection
Principle Electro Chemical Electro Chemical Galvanic Cell
Alarm Points Low 25 ppm
High 50 ppm
TWA 25 ppm
STEL 200 ppm
Low 10.0 ppm
High 30.0 ppm
TWA 10.0 ppm
STEL 15.0 ppm
Low 19.5% vol.
(decreasing)
High 23.5% vol.
(increasing)
Sampling Method Diffusion Diffusion Diffusion
Response Time T90 in 30 seconds T90 in 30 seconds T90 in 20 seconds
Accuracy ±5% of reading or
± 5 ppm CO
(whichever is
greater)
±5% of reading or
± 2 ppm H2S
(whichever is
greater)
± 0.5% O2
Safety/Regulatory
C US
186718
CSA classified, “C/US”, as Intrinsically Safe. Exia. Class I,
Groups A, B, C, & D. Class I, Zone 0, Group IIC.
Temperature Code T4.
Power Two AAA size Alkaline Batteries Standard, Duracell MN2400
or PC2400, Eveready Energizer E92 or EN92
Continuous
Operating Hours Approximately 3,000 Hours With No alarms or Backlighing
Case High-impact Plastic, Dust Proof and Weather Resistant
Standard
Accessory Wristband

3 • Specifications GasWatch 2 Operator’s Manual
Optional
Accessories • Belt Clip
• Hard Hat Clip
• Lapel Clip
Dimensions and
Weight Dimensions: 2.5 (H), 1.7 (W), 0.9 (D) inches Weight: 2 oz.
OperatingTemp.&
Humidity -10°C - 40°C, below 85% RH (non condensing)
Table 1: GasWatch 2 Specifications
GW-2C GW-2H GW-2X

GasWatch 2 Operator’s Manual Description • 4
Description
This section describes the components of the GasWatch 2. These
components include the GasWatch 2’s case, wristband, sensor cap and
sensor cover, charcoal filter disk (in the GW-2C), sensor, LCD, control
buttons, printed circuit boards, alarm lights, buzzer, vibrator, and lithium
battery.
Sensor Diffusion
Port
LCD Display Window
Alarm LED Lens
Buzzer Opening
Wristband
Control Buttons
Sensor Cap
AIR
POWER
MODE
Figure 1:Components of the GasWatch 2

5 • Description GasWatch 2 Operator’s Manual
Case
The GasWatch 2’s sturdy, high-impact plastic case is suitable for use in
many environmental conditions, indoors and out. The unit is dust proof and
weather resistant. The case has two halves, the top case and the bottom
case. They are held together by four screws in the bottom case. The case
is a different color depending on the model. The GW-2C for CO is red, the
GW-2H for H2S is orange, and the GW-2X for oxygen is blue.
The digital LCD is visible through the top case. It displays gas
concentrations, battery level, time, and other readings including TWA,
STEL, and peak gas levels. Below the LCD are two black control buttons.
The button on the left is labeled POWER/MODE. The button on the right is
labeled AIR.
To the left of the LCD is the buzzer, which is located inside the unit. To the
right of the LCD is the sensor cap which retains the sensor. Above the LCD
is a frosted lens through which the alarm lights are visible.
A battery cover is located on the bottom case and is held in place by two
screws. The wristband attaches to the bottom case.
Wristband
The GasWatch 2 comes with a wristband as a standard accessory so the
unit may be worn as a watch and allow hands-free gas monitoring. The
wristband is held in place with the same type of spring bars that are used in
a watch. The spring bars are protected by hollow tubes which fit into the
wristband. Optional accessories are available from RKI Instruments, Inc.
that can be used in place of the wristband such as a belt clip.
Sensor Cap/Sensor Cover
The sensor cap snaps onto the right side of the case and retains the
sensor. It also retains the sensor cover which is a round hydrophobic disk
membrane which protects the sensor from dirt and weather. A gasket
installed on the sensor seals against the sensor, sensor cover, and sensor
cap.
Charcoal Filter Disk in GW-2C
The GW-2C includes a charcoal filter disk which is located in a recessed
area of the sensor gasket beneath the sensor cover. The charcoal filter disk
removes gases from the sampled air that will cause a response on the CO
sensor such as H2S and certain hydrocarbons. If false or elevated CO
readings are noticed, especially in the presence of H2S, change the
charcoal filter disk (see the Maintenance section for instructions).

GasWatch 2 Operator’s Manual Description • 6
Sensor
The GasWatch 2 uses either an oxygen, CO, or H2S sensor. The sensor is
protected by the white sensor cover which is held in place by the sensor
cap and sensor gasket. The sensor cover allows ambient air to diffuse past
it to the sensor. The three sensors used in the three GasWatch 2 models
use different detection principles as described below.
Oxygen Sensor
The oxygen sensor is a galvanic type of sensor. A membrane covers the
cell and allows gas to diffuse into the cell at a rate proportional to the partial
pressure of oxygen. The oxygen reacts in the cell and produces a voltage
proportional to the concentration of oxygen. The voltage is measured by
the GasWatch 2’s circuitry, converted to a measurement of gas
concentration, and displayed on the LCD.
CO and H2S Sensors
The CO and H2S sensors are electrochemical sensors that consist of two
precious metal electrodes in an acid electrolyte. A gas permeable
membrane covers the sensor face and allows gas to diffuse into the
electrolyte. The gas reacts in the sensor and produces a current
proportional to the concentration of the target gas. The current is amplified
by the GasWatch 2’s circuitry, converted to a measurement of gas
concentration, and displayed on the LCD.
LCD
The LCD is visible through the top case. Target gas concentrations, the
time, battery condition, and alarm indications are displayed on the LCD.
When either of the control buttons is pressed, the LCD backlight comes on
for 20 seconds.
Control Buttons
Below the LCD are the two control buttons. They are POWER/MODE and
AIR. They turn on the power to the GasWatch 2 and turn it off. They control
what is displayed on the LCD, including time, gas concentrations, peak,
TWA, and STEL readings, as well as other messages. They also allow you
to perform a fresh air adjustment, change alarm points, change the time,
and calibrate the instrument. The functions performed by the control
buttons are summarized in the following table:

7 • Description GasWatch 2 Operator’s Manual
Printed Circuit Boards
The primary function of the GasWatch 2’s two printed circuit boards are to
amplify the current or voltage signal sent to them from the gas sensor,
convert the signal to a meaningful measurement of gas concentration,
display the gas concentration on the LCD, store peak, STEL, and TWA
readings, and activate the alarm circuit if an alarm point has been reached.
They monitor battery level, battery failure, and sensor failure. They also
control the GasWatch 2’s time function and the various operating modes of
the unit.
NOTE: The printed circuit boards contain no user serviceable parts.
Table 2: The Control Buttons of the GasWatch 2
Button Function
POWER/MODE
• Turns the unit on and off.
• Turns the LCD back light on.
• Displays STEL and TWA readings (GW-2H & GW-
2C).
• Displays peak readings (high for GW-2H & GW-2C
and low & high for GW-2X).
• Resets the alarm circuit (gas alarms).
• Enters Calibration Mode with the AIR button.
• Enters Alarm Adjustment Mode with the AIR
button.
• Enters Time Adjustment Mode with the AIR button.
AIR
• Turns the LCD back light on.
• Adjusts LCD readings when a fresh air adjustment
is performed.
• Enters Calibration Mode with the POWER/MODE
button.
• Enters Alarm Adjustment Mode with the POWER/
MODE button.
• Enters Time Adjustment Mode with the POWER/
MODE button.
• Increases settings when the unit is in Alarm
Adjustment Mode, Time Adjustment Mode, or
Calibration Mode.

GasWatch 2 Operator’s Manual Description • 8
Alarm Lights
The GasWatch 2 has two alarm lights located above the LCD. The alarm
lights are two red LEDs that alert you to gas, low battery, and sensor failure
alarms. They are visible through a frosted lens.
Buzzer
A solid-state electronic buzzer is mounted inside the GasWatch 2. An
opening on the left side of the top case allows the buzzer’s sound to
resonate from the case. The buzzer sounds for gas alarms, unit
malfunctions, low battery voltage, and as an indicator during normal use of
the various display options of the GasWatch 2.
Vibrator
A vibrating motor (vibrator) is mounted inside the GasWatch 2. The vibrator
vibrates momentarily during the power-up sequence and for gas alarms.
Lithium Battery
A 3.0 volt coin type lithium battery powers the GasWatch 2. The battery will
run the unit for approximately 3,000 hours when no alarms have been
activated during that time period. The battery icon on the LCD shows the
charge remaining in the battery. When the GasWatch 2 detects a low
battery voltage, a low battery warning is activated. When the GasWatch 2
determines that the battery is too low for normal operation, a dead battery
alarm is activated. The battery can be replaced by removing the battery
door in the bottom case. See the maintenance section of this manual for
instructions about replacing the battery.

9 • Start Up GasWatch 2 Operator’s Manual
Start Up This section explains how to start up the GasWatch 2 and to get it ready for
operation.
Start-up Procedure
1. Press and hold the POWER/MODE button for one second to turn on the
GasWatch 2. The the buzzer sounds briefly, the vibrator vibrates briefly,
all elements of display are activated, and the alarm lights and LCD
backlight turn on for a few seconds.
2. The GasWatch 2 then displays the target gas and time before
displaying the battery voltage. The buzzer sounds again after the
battery voltage is displayed.
CAUTION: If the unit is in low battery warning, change the battery
immediately. If the unit is in dead battery alarm, change the
battery before attempting to use the unit.
3. The gas sensor inside the GasWatch 2 begins operating and the
concentration of the target gas is displayed on the LCD. The GasWatch
2 is now in Measuring Mode. The target gas is displayed in the
appropriate units (see specifications) and the current time is displayed
at the bottom of the LCD.
NOTE: When using the GasWatch 2 for the first time, check the current
time and verify that it is correct for your time zone. If it is not, set
the time as described in “Setting the Time”.
Performing a Fresh Air Adjustment
Before using the GasWatch 2, it is a recommended to set the fresh air
reading for the target gas to ensure accurate gas readings in the
monitoring environment.
1. Find a fresh air environment. This is an environment free of toxic or
combustible gases and of normal oxygen content (20.9%).
2. With the unit on and in Measuring Mode, press and hold the AIR button
for about three seconds to allow the GasWatch 2 to set the fresh air
reading.
While you are pressing the AIR button, the LCD displays “hold”, a
prompt for you to keep pressing the AIR button.

GasWatch 2 Operator’s Manual Start Up • 10
3. When the fresh air readings have been set, the LCD displays “Adj” for 2
seconds which prompts you to release the AIR button. The unit will set
the reading to 0 ppm for the GW-2C and GW-2H and to 20.9% oxygen
for the GW-2X.
4. The unit then returns to normal operation and the display indicates the
current gas concentration.
Turning Off the GasWatch 2
1. Press and hold the POWER/MODE button for about five seconds to
turn off the unit. The buzzer will pulse while the POWER/MODE button
is being pressed before the unit turns off.
2. Release the button when the LCD is blank. The unit is off.

11 • Operation GasWatch 2 Operator’s Manual
Operation
This section describes the normal operation of the GasWatch 2. It explains
how the unit can be used to display peak, STEL, and TWA readings for the
GW-2C and GW-2C, and minimum and maximum readings for the GW-2X.
It also covers alarm indications.
Measuring Mode
After you have powered up the GasWatch 2 and performed a fresh air
adjustment following the instructions of the previous section, “Start Up”, the
GasWatch 2 is in Measuring Mode.
In Measuring Mode, the battery level, time, and target gas concentration
are displayed on the LCD. The battery icon has four bars visible when the
battery is full. As the battery charge decreases, the bars will disappear. On
the GW-2C, CO is displayed in parts per million (ppm). On the GW-2H, H2S
is displayed in ppm. On the GW-2X, oxygen is displayed as volume percent
(%).
NOTE: The time is displayed in military format with the hour going from 0
to 24.
Displaying the Peak, STEL, and TWA (GW-2C & GW-2H)
You can display the Peak, STEL, and TWA readings on the GW-2C and
GW-2H when the GasWatch 2 is in Measuring Mode using the POWER/
MODE button. STEL is an acronym for short-term exposure limit, and it is
the average reading of the target gas (H2S or CO) during the last 15
minutes. TWA is an acronym for time-weighted average, and it is the
average reading for the target gas (H2S or CO) during the last eight (8)
hours. If eight (8) hours has not elapsed since the unit was turned on, the
TWA is still calculated over eight hours, with the missing time assigned a
zero (0) value for the readings. Similarly, if the unit has not been on for 15
minutes, the missing time is assigned a 0 value and the STEL is calculated
over 15 minutes. The Peak, STEL, and TWA readings are cleared when
the unit is turned off.
0
21:19
Battery
level
Gas concentration
Time
Figure 2: LCD in Measuring Mode
ppm

GasWatch 2 Operator’s Manual Operation • 12
1. Make sure the GasWatch 2 is in Measuring Mode. The current gas
concentration should be displayed on the LCD.
2. Press and release the POWER/MODE button to enter Peak Display
Mode. This will activate the LCD backlight and display the Peak
reading. A small Peak symbol is displayed in the upper left corner of the
LCD.
3. Press and release the POWER/MODE button again to enter STEL
Display Mode. This will display the STEL reading. The word “STEL” is
displayed in the middle of the LCD above the reading.
4. Press and release the POWER/MODE button again to enter TWA
Display Mode. This will display the TWA reading. The word “TWA” is
displayed in the middle of the LCD above the reading.
5. Press and release the POWER/MODE button once again to return to
Measuring Mode.
NOTE: If you do not press a button for 20 seconds while displaying the
Peak, STEL, or TWA readings, the unit will return to Measuring
Mode automatically and the backlight will turn off.
Displaying the Min and Max (GW-2X)
You can display the minimum (Min) and maximum (Max) readings on the
GW-2X when the GasWatch 2 is in Measuring Mode using the POWER/
MODE button. The Min and Max readings are cleared when the unit is
turned off.
1. Make sure the GasWatch 2 is in Measuring Mode. The oxygen
concentration should be displayed on the LCD.
2. Press and release the POWER/MODE button to enter Min Display
Mode. This will activate the LCD backlight and display the Min reading.
A small Min symbol is displayed in the upper left corner of the LCD.
3. Press and release the POWER/MODE button again to enter Max
Display Mode. This will display the Max reading. A small Max symbol is
displayed in the upper left corner of the LCD.
4. Press and release the POWER/MODE button once again to return to
Measuring Mode.
NOTE: If you do not press a button for 20 seconds while displaying the
Min or Max readings, the unit will return to Measuring Mode
automatically and the backlight will turn off.

13 • Operation GasWatch 2 Operator’s Manual
Alarms
This section covers alarm indications. It also tells you how to reset the
GasWatch 2 after an alarm has occurred and how to respond to an alarm
condition.
Alarm Indications, GW-2C & GW-2H
The GW-2C and the GW-2H will sound an alarm and the unit will vibrate
when the target gas concentration, CO or H2S, rises above the low alarm
point. The GasWatch 2 also sounds an alarm and vibrates when the high
alarm point, the STEL alarm point, or the TWA alarm point is reached. It
also has a low battery warning, a dead battery alarm, an over range alarm,
a sensor failure alarm, and a system failure alarm. See Table 3 below for a
description of each alarm indication.
Alarm Indications, GW-2X
The GW-2X will sound an alarm and the unit will vibrate when the oxygen
concentration falls below the low alarm point or rises above the high alarm
point. It also has a low battery warning, a dead battery alarm, an over
range alarm, a sensor failure alarm, and a system failure alarm. See
Table 3 below for a description of each alarm indication.
The table below summarizes the types of alarms produced by the
GasWatch 2.
Table 3: Alarm Types and Indications
Alarm Type LCD Indications Other Indications
Low Alarm
Concentration of gas
rises above the low
alarm point, or for the
GW-2X, falls below
the low alarm point.
• Gas reading
flashes.
• Back light turns on.
• Pulsing tone once
per second.
• Unit vibrates once
per second.
• Alarm lights flash
once per second.
High Alarm
Concentration of gas
rises above the high
alarm point.
• Gas reading
flashes.
• Back light turns on.
• Pulsing tone twice
per second.
• Unit vibrates twice
per second.
• Alarm light flashes
twice per second.

GasWatch 2 Operator’s Manual Operation • 14
TWA or STEL
(GW-2C & GW-2H
Only)
Concentration of CO
or H2S risesabovethe
TWA or STEL alarm
point.
• Back light turns on.
•TWA or STEL
blinks to the left of
the battery icon.
• If the unit is in both
TWA alarm and
STEL alarm, both
TWA and STEL will
be displayed.
• Pulsing tone once
per second.
• Unit vibrates once
per second.
• Alarm light flashes
once per second.
Over Range • Gas reading
replacedbyblinking
brackets.
• Back light turns on.
• Pulsing tone once
per second.
• Unit vibrates once
per second.
• Alarm light flashes.
Low Battery Warning • Last remaining bar
on the right in
battery icon
flashes.
•None
Dead Battery Alarm • Gas reading
replaced by FAIL.
• Battery icon
flashes.
• Double Pulsing
Tone (two pulses in
quick succession)
once a second.
Sensor Failure • Gas reading
replaced by FAIL.• Double Pulsing Tone (two pulses in
quick succession)
once a second.
System Failure • Gas reading
replaced by FAIL.
• Time replaced by
SYS below FAIL.
• Double Pulsing
Tone (two pulses in
quick succession)
once a second.
Table 3: Alarm Types and Indications
Alarm Type LCD Indications Other Indications

15 • Operation GasWatch 2 Operator’s Manual
Resetting Gas Alarms
To reset a gas alarm, press the POWER/MODE button after the gas
reading falls below the low alarm point (or above for the GW-2X). If a TWA
or STEL alarm has been activated, it cannot be reset unless you turn off
the unit.
NOTE: Even though the gas concentration may have returned to normal
or may have fallen below the alarm point, the alarm indications will
continue until you have reset the alarm using the MODE/POWER
button.
Responding to Alarms
This section describes response to gas, over range, battery, sensor failure,
and system failure alarms.
Responding to Gas Alarms
1. Follow your established procedure for an increasing gas condition or a
decreasing oxygen condition.
2. Reset the alarm using the POWER/MODE button once the alarm
condition has been cleared.
Responding to an Over Range Alarm
WARNING: An over range condition may indicate an extreme toxic
gas or oxygen concentration. Confirm the gas
concentration with a different GasWatch 2 or with another
gas detecting device.
1. Follow your established procedure for an increasing gas condition.
2. Reset the alarm using the MODE/POWER button once the alarm
condition has cleared.
3. Calibrate the GasWatch 2 as described in the calibration section of this
manual.
4. If the over range condition continues, you may need to replace the
sensor.
5. If the over range condition continues after you have replaced the
sensor, contact RKI Instruments, Inc. for further instructions.