Abstract: An apparatus is used to determine whether a container moving along a conveyor is suitable for storing water. The apparatus includes a sampler that obtains a sample from the interior of the container as the container moves along the conveyor. A PID is connected to the sampler to receive the sample and produce a signal corresponding to contents of the sample. A controller is connected to the PID and receives and analyzes the signal to determine whether the container is suitable for storing water. The apparatus may include a vacuum source connected to the PID that produces a reduced pressure for drawing the sample through the PID. A flow restrictor may be positioned between the sampler and PID. The flow restrictor may provide variable resistance to set a desired clearance time through the PID and sensitivity of the PID.