Carbon Monoxide Alarm User Manual

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instrument must be manually reset before the alarms are
silenced.
1.1.5 Atmospheric hazard alarms
The PhD2 personal, portable gas
detector has been designed for the detection of
dangerous atmospheric conditions. An alarm
condition indicates the presence of a potentially life-
threatening hazard and should be taken very
seriously.
In the event of an alarm condition
it is important to follow established procedures. The
safest course of action is to immediately leave the
affected area, and to return only after further testing
determines that the area is once again safe for entry.
Failure
The combustible gas alarm is activated when the percent
LEL (Lower Explosive Limit) gas concentration exceeds
the pre-set alarm point.
A rapid up-scale reading followed
by a declining or erratic reading may indicate a
hazardous combustible gas concentration that
exceeds the PhD2’s zero to 100 percent LEL detection
range.
Two oxygen alarm set points have been provided; one for
low concentrations associated with oxygen deficiencies,
and one for high concentrations associated with oxygen
enrichment. Three alarm set points have been provided
for each toxic gas monitored; TWA (Time Weighted
Average), STEL (Short Term Exposure Limit), and
Ceiling.
Appendices A and B discuss choosing alarm levels.
The procedures for adjusting alarm set-points are
given in Chapter 4.
1.1.6 Low battery alarms
Alarms will be activated whenever battery voltage is too
low to allow the safe operation of the instrument. When
the battery voltage is reduced to 5.65 Volts, an audible
alarm sounds, and the display screen indicates a low
battery condition exists. At this stage, the low battery
alarms may be silenced for a fifteen minute period by
pressing the large black Mode push-button. The alarm
will continue to sound every fifteen minutes until the
voltage reaches 5.55 Volts.
When the battery voltage is reduced to 5.55 Volts, the
battery alarm will sound every 30 seconds. At this point it
is no longer safe to continue to use the instrument until
the battery has been recharged, and it is necessary to
leave any hazardous area in which the instrument is
being used immediately.
When the battery voltage is reduced to 5.45 Volts, the
PhD
2
will display a "Dead Batt" message to warn the user
of imminent shut down. The instrument will then
automatically turn itself off, protecting the battery from
deep discharge.
After any low battery alarm the PhD
2
battery must
immediately be recharged.
1.1.7 Other alarms and special
microprocessor features
Combustible sensor “over-limit” alarm latch:
Protective software “latches” the combustible alarm when
the sensor is exposed to 100 % LEL combustible gas.
The alarm sounds continuously until the instrument is
manually reset. (Discussed in detail in Section 3.2.2.)
Missing or failed combustible sensor: Display shows
“X” instead of normal combustible gas reading. (This
alarm will not be triggered when sensor failure is due to
poisoning.)
Over-limit or failed toxic gas sensor: Numeric toxic
gas readings of affected sensor blink.
Downscale or negative reading alarm: Audible and
visual alarms for the affected sensor are activated when
negative readings equal one-half of TWA alarm value.
(As an example, if the TWA alarm is set at 15 PPM,
readings of minus 7.5 PPM would activate this alarm.)
Several automatic programs prevent tampering and
misuse of the PhD
2
by unauthorized persons. Each time
the detector is turned on, an electronic self-test is
performed that assures the user of proper performance.
The sensors, the LED alarm lights, and audible alarm are
automatically tested, and the battery is monitored
continuously for proper voltage. A diagnostic routine for
advanced PhD
2
users or service technicians provides a
means for technical evaluation of sensor performance.
The PhD
2
automatically remembers (logs) gas readings,
as well as other important information such as turn-on /
turn-off times, temperature, battery condition, and
whenever the instrument is calibrated.
The PhD
2
can store up to 3,000 data points, enough for
the storage of up to 50 hours of four gas monitoring
broken into as many as 36 individual monitoring
"sessions." User selectable data-logging intervals allow
the collection of data for monitoring projects of even
longer duration.
This information may be downloaded to a computer to
create a permanent record, or directly displayed on the
PhD
2
meter screen. A PhD
2
Gas Detection Database
program and Computer Link Kit is optionally available,
and recommended for users wishing to interface their
PhD
2
with a computer.
Chapter 5 describes PhD
2
advanced technical
features in greater detail. Chapter 6 describes record
keeping and datalogging.