3
PRINCIPLE OF OPERATION
A sample pump draws particle-laden air at a
fl
ow rate of 10 L/min through an iner-
tial impactor to separate airborne particles according to aerodynamic diameter.
See
Figure 2.
Particles enter the impactor through eight nozzles on top of the sampler.
The inlet nozzles are sized to operate at a 10 L/min
fl
ow rate, causing eight airjets
to impinge onto the impaction disc positioned below the inlet nozzles. Particles
larger than the sampler cut-point with enough inertia to cross the airstream lines
impact on the impaction disc. The air
fl
ow, containing smaller particles, makes a
sharp turn, passes through the openings in the top of the
fi
lter casse
tt
e, and follows
through to a 47-mm
fi
lter where the smaller particles collect.
The top of the
fi
lter casse
tt
e accommodates the impaction disc. For optimum impac-
tor performance, a 37-mm oiled porous plastic disc is recommended as disposable
collection substrate (supplied with system). If chemical analysis of larger particles
is desired, a 37-mm
fi
lter (quar
tz
or PTFE) may be used.
Inlet
PTFE O-ring
Impaction disc
BUNA-N O-ring
Exhaust
The two main components of the DPS System:
IMPACT Sampler and Leland Legacy Sample Pump
Exploded view of IMPACT Sampler
Rain cover
Air
fl
ow
Air
fl
ow
Air
fl
ow
Air
fl
ow
Air
fl
ow
Filter cassette top
Collection
fi
lter
Stainless steel support
Filter cassette bottom
Figure 2.
IMPACT Sampler and Leland Legacy Sample Pump
