Two types of carbon nanotubes [single walled nanotubes (SWCNTs) and multi walled carbon nanotubes (MWCNTs)] are deposited on porous silicon by the drop casting technique.Upon exposure to test gas mixing ratio 3％ NO2,the sensitivity response results show that the SWCNTs’ sensitivity reaches to 79.8％,where MWCNTs’ is 59.6％.The study shows that sensitivity response of the films increases with an increase in the operating temperature up to 200℃ and 150℃ for MWCNTs and SWCNTs.The response and recovery time is about 19s and 54s at 200℃ for MWCNTs,respectively,and 20s and 56s at 150℃ for SWCNTs.