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A4OM 2.2.1 QA/QC Sample Designation Sample duplicates will be labeled numerically and will not indicate the point from which the sample was collected. Times for all duplicate samples will be 12:00 on the day of sampling. 2.3 Sample Collection Prior to sampling, each canister will have its vacuum checked with a dedicated gauge, with the expected vacuum ranging from -28 to -29" Hg. If any canister differs from the others by 3" Hg or more, the canister will not be used as the integrity of the canister may have been compromised. Building conditions should reflect current occupancy conditions, including typical use of any HVAC system. The occupant will not make changes to the building envelope during sampling that could potentially alter results (i.e. leaving a window or door open). 1) The canister will be placed such that the inlet is at breathing height, between 3 ft and 5 ft above the floor. a) This height can be achieved using a stand or table, if available, or through attaching a short length of stainless-steel or Teflon tubing to the Summa®canister using stainless steel air-tight fitting and attached to the inlet of the tubing. b) The intake of the tubing will be located at approximately breathing height. 2) Both ambient air canisters and indoor air canisters will be set-up prior to opening the canister valves. 3) Once the canisters are in place, the valve of the indoor air canister will be opened, and the start time and vacuum gauge reading will be recorded. This process is repeated for each other canister as quickly as possible. 4) Each indoor air canister will be equipped with an 8-hour flow controller, for commercial non-residential buildings, or a 24-hour flow controller for residential buildings. After 8 or 24 hours and when the pressure is at approximately 5" Hg, the valve will be closed, and the final vacuum and time will be recorded. 2.4 Ambient Air Samples Ambient (i.e., outdoor) air samples are helpful to identify potential contributions to indoor air concentrations from building air exchange with outdoor air and will be collected any time indoor air samples are collected. • Locations for ambient air samples will include one upwind, one downwind, and one crosswind location.