Scrubbers lose as much as one-third of their airflow after just one cut [Schultz and Fields 1999]. The most common cause of efficiency loss is filter panel clogging. Pitot tubes should be used to obtain air velocity readings as a measure of scrubber performance. When the dust is excessive, cleaning of the filter panel (Figure 4-7), the demister (Figure 4-8), and the scrubber ductwork is required more often. Also, the spray nozzles in the ductwork should be checked to ensure they are completely wetting the entire filter panel and not just the center