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that the various pieces of equipment, when assembled, cannot be rotated by hand. • Verify Gauge Operation: If the indicator does not read "zero" upon arrival, the gauge either needs to equilibrated or the gauge may be damaged and unusable. Equilibrate the gauge by "cracking" the rubber plug on top of the gauge. For more details on the equilibration procedure, see instructions included with the gauge or call Client Services at 800-985-5955. • Verify Initial Vacuum of Canister: Prior to shipment, each canister is checked for mechanical integrity. However, it is still important to check the vacuum of the canister prior to use and record the initial vacuum on the chain-of.-custody. The initial vacuum of the canister should be greater than 25 in. Hg. If the canister vacuum Is less than 25 in. Hg, do not use it. Call Client Services at 800-985-5955 and arrange for a replacement canister. If sampling at altitude, there are special considerations for gauge readings and sampling (see Section 5.2). The procedure to verify the initial vacuum of a canister is simple, but unforgiving. 1. Confirm that valve is closed (knob should already be tightened clockwise). 2. Remove the brass cap. 3. Attach. gauge. 4. Attach brass cap to side of gauge tee fitting. 5. Open and close valve quickly(a few seconds). 6. Read vacuum on the gauge. 7. Record gauge reading on "Initial Vacuum" column of chain-of-custody. 8. Verify that canister valve is closed and remove gauge. 9. Replace the brass cap. • Leave Residual Vacuum: A grab sample can.be collected either by allowing the canister to reach ambient conditions or by leaving some residual vacuum (e.g., 5 in. Hg) in the canister. In either case, the final vacuum should be noted on the "Final Vacuum" column on the chain-of-custody. This will enable the laboratory to compare the final vacuum with the receipt vacuum (i.e., the vacuum measured upon arrival at the laboratory). If the two readings differ significantly, Client Services will contact you for instructions on how to proceed. 3.1.1 Step-By-Step Procedures for Canister Grab Sampling These procedures are for a typical ambient air sampling application and actual field conditions and procedures may vary. Before you get to the field: 1. Verify contents of the shipped package (e.g., chain-of-custody, canister,particulate filter,and gauge—if requested). 2. Verify that gauge is working properly. 3. Verify and record initial vacuum of canister. AIR TOXICS LTD. 9