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gas. Failure to check accuracy can lead
to inaccurate and potentially dangerous
readings.
Calibration is a two step procedure. In the
first step the Toxi Plus is taken to an area
where the atmosphere is fresh and a "zero"
adjustment is made. The second step of
the calibration procedure is the sensor
response or "span" adjustment. In this
step the toxic sensor is exposed to known
concentration calibration gas. If the
instrument notes there is a deviation from
the expected response, it will automatically
adjust itself so that the readings match the
concentration of the gas being used.
Calibration procedures are discussed in
detail in Chapter 3.
1.5 Display backlight
A manually activated display backlight
allows the LCD to be read in dim light
conditions. Pressing the on/off MODE
button once at any time during normal
operation causes the backlight to be
activated for 10 seconds. In the event of a
gas alarm the backlight turns on
automatically and remains on until the
alarm condition clears.
1.6 Alarm logic
Toxi Plus alarms are user adjustable and
may be set anywhere within the range of
the sensor. When an alarm set point is
exceeded a two-toned audible alarm
sounds, a bright red LED alarm light
flashes, and (if equipped) the optional
vibrator type alarm is activated.
Toxi Plus alarms are normally self-
resetting. When readings drop back below
the pre-set alarm levels, the instrument
returns to normal operation, and the visual
and audible alarms cease.
Toxi Plus alarms may also be set so that
they "latch." With the alarms latched, once
an alarm occurs both visual and audible
alarms continue to sound even after the
atmospheric hazard has cleared. The
instrument must be manually reset to
silence the alarms.
Procedures for latching Toxi Plus alarms
are given in Chapter 4.
1.6.1 Atmospheric hazard
alarms
The Toxi Plus 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 to
immediately leave the area may result in
serious injury or death.
Three alarm set-points have been provided
for Toxi Plus detectors: TWA (Time
Weighted Average), STEL (Short Term
Exposure Limit), and Ceiling. Toxi Plus
alarm settings are set at the factory in the
most conservative way possible.
The procedures for adjusting alarm set
points or restoring the factory default
settings are given in Chapter 4.
1.6.2 Low battery alarms
The Toxi Plus uses 3 AAA alkaline
batteries for power. A fresh set of batteries
should provide up to 1,500 hours of normal
operation.
When it is time to replace the batteries a
"B" will appear in the lower left hand corner
of the display screen, and the audible
alarm will “beep” once per minute until the
battery is replaced. The user should have
approximately one to two weeks of useful
life remaining. Batteries should be
replaced as soon as possible after any low
battery message is displayed.
