A method and device for the detection of low-level harmful substances in a large volume of fluid comprising using a concentrator system to produce a retentate and analyzing the retentate for the presence of at least one harmful substance. The screw has a rod body and higher thread and lower thread formed on the rod body. The certificate includes security information about a site maintained at the remote device. The embodiments of the disclosure optionally generate an accessibility script in a selected format. The messages are controlled in time by a first station.