TY - RPRT TI - Performance tests of two cleanable impingement air filters Vortox types VN1 and VN2 : manufactured by Vortox Company Claremont, California AU - Coblentz, Carl W AU - Achenbach, Paul R PY - 1958 PB - National Bureau of Standards CY - Gaithersburg, MD SN - NBS RPT 6251 DO - 10.6028/NBS.RPT.6251 ER -