In order to improve the selectivity of polypyrrole based sensors towards acetone and toluene, which are flammable components of lacquer over the non-flammable components acetic acid and water, polypyrrole doped with alpha-naphthalene sulfonate (PPy/alpha-NS-) has been blended with several insulating polymers. PEO, PMMA, HDPE, PS and ABS were mixed with polypyrrole (PPy) by three different methods: dry mixing, solution mixing, and coating. The specific conductivity values of these blends were reduced by 1-4 orders of magnitude relative to that of pure PPy/alpha-NS-, depending on the polymer added and the method of mixing employed. The surface composition and water wetting ability of the samples were investigated by XPS and optical microscope techniques, respectively. The blends from solution mixing of PPy/alpha-NS-/PMMA, PPy/alpha-NS-/PS and PPy/alpha-NS-/ABS were found to be more sensitive towards acetone and toluene but less sensitive towards water, relative to pure PPy/alpha-NS-. However, the sensitivity towards acetic acid was not significantly altered from that of pure PPy/alpha-NS-. (C) 2004 Elsevier B.V.. All rights reserved.