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Associated hardware used with the canister includes the valve, brass cap, particulate filter, and vacuum gauge. 2,2.1 Valve An industry standard, 1/4 in. stainless steel bellows valve (manufactured by Swagelok or Parker Instruments) is mounted at the top of the canister. The valve allows vacuum to be maintained in the canister prior to sampling and seals off the canister once the sample has been collected. No more than a half turn by hand is required to open the valve. Do not over-tighten the valve after sampling or it may become damaged. A darnaged valve can leak and possibly compromise the sample. Some canisters have a metal cage near the top to protect the valve. 2.2.2 Brass Cap Each canister comes with a brass cap (i.e., Swagelok 1/4 in. plug) secured to the inlet of the valve assembly. The cap serves two purposes. First, it ensures that there is no loss of vacuum due to a leaky valve or valve that is accidentally opened during handling. Second, it prevents dust and other particu- late matter from fouling the valve. The cap is removed prior to sampling and replaced.following sample collection. b Always replace the brass cap following canister sampling. 7 Micron 2 Micron 2.2.3 Particulate Filter Particulate filters should always be used when sampling with a canister. Separate filters are provided to clients taking a grab sample. Filters are included in the flow controllers for clients taking inte- grated samples. Air Toxics Ltd. provides either a 2 micron filter or a 7 micron falter. These devices filter particulate matter greater than. 2 and 7 micron. in diameter respectively. The shorter 2 micron filter is a fritted stainless steel disk that has been pressed into a conventional Swagelok adapter and is disposed of after each single use. This device has a relatively high pressure drop across the fritted disk and restricts the flow into the canister. The 2 micron filter is standard for clients taking inte- grated samples. The longer 7 micron filter is cleaned in a similar manner as the stainless steel canisters after each single use and does not significantly restrict the flow rate into the canister. The 7 micron filter is primarily used with grab samples. Both the 2 and 7 micron filters are not calibrated devices and therefore the flow rates can and do vary for each filter. * Always use the particulate filter for canister sampling. AIR TOXICS LTD. 6