Acid‐washing Whatman 41 or 0.45 μm pore size Nuclepore filters resulted in substantial reduction of the trace metal contents and variability in both types of filters for most of the metals examined. No changes in the air flow rate or retention properties of the Whatman 41 filters were observed to occur as a result of this procedure. The advantages of the lower trace metal blank concentrations and uncertainties resulting from this procedure were discussed with reference to the collection of extremely low level trace metal environmental samples.