EPA's Region 6 Office
Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations
Synchronous Canisters
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Collecting Synchronous Canisters
The following describes the synchronous sampling of two co-located canisters designed for sampling (i.e., the second unit is not a "field blank" or a "field spike).
Both canisters should have been obtained from the lab or coordinator together, their gauge readings should be at >-25 inches of mercury. Any canister whose pressure is below -25" Hg, for example -20" Hg, may be leaking and it should be returned to the lab or hub for a replacement before any sampling is done.
Note the identity number, including the letter prefix, on the Chain-of-Custody but wait until you get on-site before noting the gauge reading.
At the sampling site:
1. Remove the canisters from their protective cases. Note the gauge readings on the chain-of-custody.
2. Locate the two canisters at the same height and as close to one another as possible.
3. Remove the dust cover (1/4" brass plug) from both inlets. Observe that there is no dirt in the inlet. Make sure that no dirt gets in the inlet while the plug is off. Try to avoid getting water or rain droplets into the inlet, but if any of this occurs, please so note on the chain-of-custody.
4. Note your watch or timing device for the appropriate start time - reset
if needed.
5. Simultaneously, open the green valve slightly (1/4 turn) on both units
at the same time. If you remain on sight and can visually observe the
gauge, verify that the pressure is rising (i.e. going from 25 inches of
mercury toward 0 inches of mercury).
6. After three minutes, close the canister (green) valve on both canisters
finger tight and with no excessive force. Replace the dust covers.
6. Note the gauge reading on both canisters and record on the chain-of-custody.
7. Place the canisters into the protective box
8. Fill out the chain-of-custody and follow that procedure.