In this paper, a spiral shape photonic crystal fiber (S-PCF) has been suggested as a gas sensor for detecting toxic or colorless gases as well as monitoring the air pollution by metering gas condensate elements in production facilities. Our reported S-PCF is micro-structured where two layers porous core is encircled by a spiral shape cladding. The geometrical parameters have altered to optimize the parameters of the proposed structure. The numerical analysis of the proposed S-PCF is performed by utilizing finite element method (FEM). The relative sensitivity and birefringence of the proposed S-PCF are 55.10% and 7.23 × 10^− 3 respectively at the 1.33 μm wavelength that lies in the absorption line of toxic gases (methane and hydrogen fluoride). Besides, effective area, nonlinear coefficient and V parameters are also described briefly.