PM400 Multi-Gas Personal Monitor
REV – 2.0
[34-2900-0206-2 ]
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P a g e
1.3
Difference Between PM
400
P and PM
400
IR
The PM
400
P and the PM
400
IR are identical units with one exception: The Combustible gas (LEL) sensors are different
in each model. The PM
400
P is equipped with
a Catalytic Bead (Pellistor) sensor
. The PM
400
IR is equipped with a
Non-Dispersive Infra-Red (NDIR) sensor
. Be sure to understand the strengths and limitations of the sensor that’s
inside the unit (see below). They directly affect the usage and the lifespan of your detection device.
1.3.1
Over Range Alarm Function
Because of the nature of each sensor, the device will behave differently when exposed to high gas levels which
exceed their sensor ranges this is known as an Over Range Alert.
1.3.1.1
PM
400
P
In the event of an Over Range alarm, the Catalytic Bead sensor will prompt Over Range alarms and then turn off the
sensor to avoid damaging the sensor elements.
If an Over Range Alarm sounds, exit to a safe area immediately.
The alarm will continue to sound because the sensor is disabled. To silence the alarm, the monitor will need to be
turned off and back on again, thus re-enabling the sensor.
1.3.1.2
PM
400
IR
In the event of an Over Range alarm, the NDIR sensor continues to function normally.
If an Over Range Alarm sounds, exit to a safe area immediately.
A simple press of the [Function] key acknowledges and silences the alarm. The sensor continues to stay active even
though the level has exceeded 100% LEL.
1.3.2
Catalytic Bead technology (PM
400
P) Overview
1.3.2.1
Advantages of Catalytic Bead technology
•
The Catalytic sensor detects a wide range of combustible (LEL) gasses:
The PM
400
P is the device that should
be used if hydrogen and acetylene are among the gases in your environment that require detection.
Make careful note of the disadvantages of this sensor listed below; they have a direct effect on user safety and on
the function of the device.
1.3.2.2
Disadvantages of Catalytic Bead technology
•
The Catalytic sensor can be “poisoned”:
Certain chemicals will damage the internal elements and cause the
sensor to lose sensitivity. Common poisons are chemicals which contain silicon (found in hand lotions and
industrial lubricants) and Sulfur compounds, which can be released with gases. Chlorine (found in many
cleaning products) and heavy metals can also poison a catalytic sensor. This list is by no means
comprehensive.
•
The Catalytic Bead sensors require oxygen to detect gases:
Because a Catalytic Bead sensor burns the
sample of gas, oxygen is required for the monitor to detect the presence of combustible gases.
•
The Catalytic Bead sensor can burn out:
Exposure to high concentrations of gas can completely disable the
sensor. See section 1.3.1 Over Range Alarm Function.
