Tisch Environmental 1-TSP-AND-PM10 sales@tisch-env.com www.tisch-env.com Page 38 of 185
Take care that other filter media in the chamber does not contaminate the filters
such as quartz and glass filter fibers. Filters should be conditioned in their filter-
handling container such as a slide petri dish. Write the filter’s unique filter ID
onto the container’s label. During conditioning, place the lid so it partially
covers the open container.
Ensure with the use of lot blanks that the filter lot does not exhibit weight loss
of more than 15µg per week.
Pre-weighing of unexposed filters
The filters must be weighed in the same room as they were conditioned in.
Record the %RH and temperature and verify the mean temperature and %RH
for the last 24 hours has remained between 20-23ºC (with instantaneous
readings within ±2ºC) and 30-40% RH (with instantaneous readings within
Using clean forceps two working mass reference standards must be weighed as
a QC check such as 100mg and 200mg. Record these weights. If these weights
disagree by more than 3µg from their actual weight, they must be reweighed.
Weigh enough laboratory blanks to provide at least 10% or at least one
laboratory blank during the post sampling weighing session. Also, weigh
enough field blanks to meet 10% or at least one field blank during the post
weighing session.
Weigh each filter on the microbalance. Follow the microbalance
manufacturer’s operations manual for proper operation of the microbalance.
The filters should be handled with forceps and only held by the right. Pass the
filter, support ring side up near an antistatic strip for 60 seconds before
weighing. Immediately transfer the filter to the microbalance for weighing.
Record the filter ID, lot number and tare-weight (pre-weight).
After every 10 filters, reweigh one of the standards and record the data. These
standards should be within 3µg. Also reweigh one of the 10 filters. It must be
within 15µg of its original weight.
After all the filters are weighed, both working standards should be reweighed
and must be within 3µg of their standard. Also one random filter of the total
should be reweighed and it must be within 15µg of its original weight.
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