SKC 225-390 IMPACT Sampler - Manual (Page 2)

2
Principle of Operation
Inertial impaction is employed to separate airborne particles according to their
aerodynamic diameter. A sample pump draws particle-laden air at a fl ow rate of
10 L/min through an inertial impactor to separate airborne particles according to
their aerodynamic diameter. Airfl ow enters 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 substrate. The airfl ow, containing smaller
particles, makes a sharp turn, passes through the openings in the top of the fi lter
cassett e, and follows through to a 47-mm fi lter where the smaller particles collect.
The top of the fi lter cassett e accommodates the impaction disc. For optimum impactor
performance, a 37-mm oiled porous plastic disc is recommended as disposable
impaction substrate. If chemical analysis of the larger particles is desired, a 37-mm
fi lter (quartz or PTFE) may be used.
To sample PM Coarse
(PM10-2.5)
, a coarse ring accessory can be added to an IMPACT
PM10 Sampler or an IMPACT PM Coarse Sampler may be selected (see Ordering
Information). Additional impaction and collection media are required for PM Coarse
sampling.
Media Preparation
Collection Filters: Equilibrate and preweigh fi lters in a clean environment according
to appropriate procedures. Record the weight as the pre-sample weight.
Impaction Disc: Ready-to-use pre-oiled disposable plastic impaction discs are available
as SKC Cat. Nos. 225-395 (qty. 25) and 225-395A (qty. 50). Using an oiled impaction
disc reduces particle bounce.
37-mm fi lters (quartz or PTFE) may be used if chemical analysis of larger particles
is desired.
PM10 inlet
PTFE
O-ring
37-mm
impaction
disc
Filter
cassette
BUNA-N
O-ring
Exhaust
Collection
fi lter
Stainless
steel
support
PM10 inlet
37-mm
impaction
disc
Filter
cassette
top
Filter
cassette
bottom
Exhaust
PM2.5 inlet
(
coarse ring)
37-mm fi lter
Filter cassette
top
Stainless steel
support
Filter
cassette
bottom
Exploded view of IMPACT PM10 Sampler Exploded view of IMPACT PM Coarse Sampler
(O-rings not shown)
47-mm fi nal
collection fi lter