10
remote location to the sensor
compartment. Allow one squeeze of
the bulb for every one foot of sampling
hose for the sample to reach the
sensors. Continue to squeeze the bulb
for an additional 45 seconds or until
readings stabilize.
6. Note the gas measurement readings.
CAUTION: Hand aspirated remote
sampling only provides continuous gas
readings for the area in which the probe is
located when the bulb is being
continuously squeezed.
Note: Each time a reading is desired, it is
necessary to squeeze the bulb a sufficient
number of times to bring a fresh sample to
the sensor compartment and to continue
to squeeze the bulb until readings
stabilize.
3. Calibration
The ToxiPro features fully automated fresh
air/zero and span calibration functions. The
MODE button is used to initiate the automatic
calibration sequence. Calibration
adjustments are made automatically by the
instrument.
3.1
Verification of accuracy
3.1.1 Verifying accuracy and response:
ToxiPro O
2
To verify the accuracy of the ToxiPro O
2
, take
the ToxiPro O
2
to an area where the
atmosphere is known to be fresh and check
the readings. If the readings differ from those
expected in fresh air (oxygen monitors should
read 20.9% in fresh air), then a fresh air/zero
calibration adjustment must be made as
discussed below in section 3.3. If fresh air is
not available, see section 3.7 below for
instructions for calibrating the ToxiPro O
2
in
contaminated air.
Sperian Instrumentation also recommends
that the response of the oxygen sensor be
regularly verified by any of these methods:
•
Expose the O
2
sensor to a known
concentration of gas containing less than
19.0% oxygen. If the descending oxygen
alarm is set to 19.5% the instrument
should go into alarm a few seconds after
the gas reaches the sensor face.
•
Process the ToxiPro O
2
in an IQ Express
Dock that has a cylinder of calibration gas
containing 18.0% oxygen (or less)
connected to the gas port and proceed
with the oxygen bump test.
•
Breath test: Hold your breath for 10
seconds, then
slowly
exhale directly onto
the face of the sensor (in the same way
you would to fog up a piece of glass). If
the descending oxygen alarm is set to
19.5%, the instrument should go into
alarm after a few seconds.
3.1.2 Verifying accuracy: ToxiPro with
toxic gas sensor
Verification of accuracy is a two-step
procedure for ToxiPro instruments equipped
with a toxic gas sensor:
Step one is to take the ToxiPro to an area
where the atmosphere is known to be fresh
and check the readings. If the readings differ
from those expected in fresh air (instruments
equipped with a toxic sensor should read 0
PPM in fresh air), then a fresh air calibration
adjustment must be made as discussed
below in section 3.3.
Step two is to test sensor response by
exposing the sensor to a test gas of known
concentration. This is known as a functional
(bump) test. Readings are considered to be
accurate when the display is between 90%
and 120% of the expected values as given on
the calibration gas cylinder. If readings are
accurate, there is no need to adjust your gas
detector. See section 3.4 for further details
concerning the functional/bump test.
If the readings are inaccurate, the instrument
must be span calibrated before further use as
discussed in section 3.5.
The accuracy of
ToxiPro instruments equipped with toxic
gas sensors should be checked
periodically with known concentration
calibration gas. Failure to check accuracy
can lead to inaccurate and potentially
dangerous readings.
See Appendix C for a discussion of
calibration frequency recommendations.
3.2
Effect of contaminants on ToxiPro
sensors
The atmosphere in which the ToxiPro is used
can have lasting effects on the sensors.
Sensors may suffer losses in sensitivity
leading to degraded performance if exposed
to certain substances.
The ToxiPro O
2
uses a galvanic oxygen
sensor, while toxic sensor versions of the
ToxiPro use an electrochemical toxic gas
sensor. Different types of sensors use
different detection principles, so the
conditions that affect the accuracy of the
sensors vary from one type of sensor to the
next.
3.2.1 Effects of contaminants on O
2
sensors
Oxygen sensors may be affected by
prolonged exposure to "acid" gases such as
