Casella CEL Airborne bacteria sampler - Manual (Page 10)

Once selected, slits in the sampling head should be closed to leave the
appropriate number of slits open for the desired flow rate, as presented in
the table. The slits are closed by placing the metal blanking-off strips into the
slit grooves in the top of the sampling head and securing them with adhesive
tape. To place the blanking-off strips in the slits, remove the inlet nozzle on
the top of the sampler and replace after the strips have been positioned.
When sampling begins the pump speed control F (Figure 3) should be
adjusted, so that the needle of the vacuum gauge points to the correct
indicator for the desired flow rate.
5.6 Commencement of Sampling
To commence sampling airborne bacteria, depress switch G (located at the
top right hand corner of the sampling unit’s control panel, Figure 2), so that it
switches from single rotation to continuous rotation as indicated on the
panel.
If continuous rotation of the turntable is required leave the switch in that
position, however if only a single rotation is required return the switch back
to the single rotation position after three seconds.
The pump and turntable should have started when the switch was depressed
and the time at which sampling commenced should be recorded.
Remember to set the flow rate, by adjusting the pump speed controller to
achieve the desired reading on the vacuum gauge as described in Section 5.5
above, when sampling starts.
During sampling and when a single rotation of the turntable is used over a
sample period of up to five minutes, events which may result in high airborne
bacteria concentrations can be marked on the surface of the agar, by the
quick depression of switch H on the front of the sampling unit control panel.
Depression of the switch causes a solenoid to be momentarily energised,
which makes a lever press into the surface of the agar so that the area of the
plate on which bacteria are being deposited can be identified later, allowing it
to be linked to subsequent counts.
Note that the switch should only be depressed momentarily to avoid the
lever jamming in the agar and preventing plate rotation.
5.7 Sampling Times
The sampling times employed are at the discretion of the operator and are
dependant on the expected level of bacteria present and the flow rates used.
Operation
Page 10 of 16
BACTERIA SAMPLER
User Manual