OZONE MONITOR BMT 932 Manual, Rev. 02/2021
10
By means of a solenoid valve assembly, the sample gas is delivered directly to the cuvette, or via
an ozone scrubber with high selectivity to ozone alone. During this phase (with no ozone in the
cuvette) the photometric ozone signal is set to zero. The scrubber thus is the element which shall
give the zero ozone reference. From time to time, a solenoid valve switches an ozone generator
in front of the scrubber to check its ability to remove any ozone from the sample.
In case the utility scrubber fails to remove the ozone completely, another scrubber (the reserve
scrubber) is switched into the circuit, and SCRUBBER WARNING is activated to tell the user
that the utility scrubber has to be replaced soon. The OZONE MONITOR contains an ozone
destruct to remove any ozone from the sample leaving the instrument. But it does not contain a
sample gas filter. The reason is that any sample filtering should be performed at the inlet of the
sampling tube to protect the inner tube surfaces from becoming dirty. The sample gas filters
shipped with the instrument have to be provided at the inlets of the sample tubes, and have to be
replaced on a regular basis (see page 13).
8
Scrubber
The scrubber is one of the most important elements of an ambient ozone monitor. It shall re-
move any ozone in the sample gas whilst it shall not affect any other substances which could
produce an extinction of the UV radiation. Perhaps not any kind of scrubber really fulfills these
demands perfectly.
The non-ideal behaviour of a scrubber material of course depends upon the species and quanti-
ties of substances contained in the sample air which may be affected by the scrubber. In other
words: The optimal choice of a scrubber material always depends upon the situation in which the
ozone monitor is operated.
For ambient ozone monitoring (instruments with measurement range 1 ppm
v
) we are using the
scrubber material which seems to be the best choice today. But we are continuously looking for
the performance of our scrubber in order to eventually find even better solutions.
ATTENTION:
The ambient scrubber material is a consumable. Excessive ozone concentra-
tions can dramatically shorten the scrubber life. Therefore, during startup, if there are gross
ozone leaks, it may be necessary to replace the ambient scrubber several times.
For all applications of the OZONE MONITOR BMT 932 which are not for ambient monitoring
(TLV monitoring), and for all ranges higher than 1 ppm
v
, we are using a catalytic scrubber mate-
rial which is not a consumable, but eventually can be destroyed or deteriorated, of course.
9
Mechanical Installation
The OZONE MONITOR BMT 932 is in a 19'' rack mount enclosure, 132.5 mm high, 300 mm
deep (see Figure 3), or in a splash-proof wall mounted aluminium cabinet 357 x 440 x 133 mm.
Additional room for cables and tubing should be provided about 120 mm behind the back panel
of the rack mount instrument. Free air circulation should be provided around this instrument for
convection cooling. Temperature of the ambient air should be in the range of 0 to 45°C (non-
condensing).
