Patent ID: 8875589

Claim:
A sampling and counting system for use in testing the efficiency of a HEPA filter by comparing particle counts of upstream and downstream samples with respect to the HEPA filter under test, the sampling and counting system comprising: a particle counter, the particle counter having an inlet and an exhaust outlet, the particle counter having a sample flow rating; and a sampling system for processing upstream and downstream samples, wherein the sampling system is connected to both the inlet and exhaust outlet of the particle counter, and wherein the sampling system incorporates a means for balancing fluid flow rate of upstream and downstream samples through the particle counter; and an upstream rotameter, the upstream rotameter being located between an upstream sample receiving line and a vacuum line, the upstream rotameter having an upstream rotameter flow rate, and a downstream rotameter, the downstream rotameter being located between a downstream sample receiving line and the vacuum line, the downstream rotameter having a downstream rotameter flow rate, and wherein each of the upstream and downstream rotameter flow rates are between 5% and 60% above the sample flow rating of the particle collector.