| Step 1: |
Sample the air as per standard method.
|
| Step 2: |
Open cassette so as to free the filters,
replace the top of the cassette loosely in the bottom part and place the
entire cassette in a 40° Celsius oven or a dessicator for 20-25 minutes.
This warming will help separate the two membranes and make it easy to remove
the top filter.
|
| Step 3: |
Remove the cassette and let it acclimate
to the laboratory's environment. (about 20 minutes).
The filter must be at room temperature and at the ambient relative humidity
of the laboratory before weighing, other wise the filter will be shedding
or absorbing a slight amount of moisture causing drift in the weighing
step.
|
| Step 4: |
Be sure you have removed the cassette's
bottom plug, proceed to place the cassette on
the Filter Popper tm (Cat # APFLTPR-M),
gently lowering it so the post raises the pad with the two filters,above
the lip of the cassette. The filters are now accessible to be removed.
|
| Step 5: |
Using a pair of norrserrated blunt nose
forceps (Cat# APFORCEPS), separate and remove the top filter carefully
so as to maintain it as level as possible.
|
| Step 6: |
Pass the Filters over a static elimination device to remove static charges that build up on all membrane filters.
|
| Step 7: |
Gently place filter on the pan of your
microbalance and weigh the filter.
|
| Step 8: |
Record the weight of the top filter.
|
| Step 9: |
Remove bottom filter from support pad.
|
| Step 10: |
Repeat Step 6 through 8
with the bottom filter.
|
| Step 11: |
Subtract the weight of the bottom filter
from the weight of the top filter. The
difference is the weight of the contaminant, within
plus or minus the matching differential of the Matched Weight filters. |
Note:- Under certain conditions,
a negative weight can be obtained if the amount of contaminant collected
less than the weight differential
of the matched weight filters and the bottom filter happens to be the heavier
filter of the pair. This
does not indicate an error but rather that too little a contaminant has
been collected. Low
contaminant levels can occur if too short a sampling time has lapsed or
the environment is very clean. Consult the specifications of the particular
matched weight filter being used to determine the limits.
|
