Can Contractor employee on the service contract be the ordering official, and point of contact for the filter supply contract?
According to FAR 3.1101, providing advice and recommendations with regard to "evaluating contactor performance" and "determining what supplies or services are to be acquired" are each considered to be an "Acquisition function closely associated with inherently governmental functions." Note the point about "providing advice and recommendations." FAR 7.503(c) generally considers those functions as inherently governmental.
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If there is a contractor employee actually inspecting supplies, and that inspection is the basis for approving invoices, then that could be a problem. Likewise, having a contractor employee order supplies, especially if by "ordering" he/she could be construed as obligating the Government, then this could be a problem too.
Given these concerns, I highly recommend you consult your organization's legal counsel for an evaluation of your situation.