This article represents a gas sensor based on spiral photonic crystal fiber (S-PCF) for detecting harmful or colorless gasses and monitoring air pollution by metering gas condensate elements in production facilities. The proposed micro-structured S-PCF contains two layers porous core encircled by a spiral shape cladding. The geometrical parameters are tuned to fix the optimized S-PCF structure. The numerical analysis of the proposed S-PCF is performed by utilizing finite element method (FEM) with circular perfectly match layer (C-PML). The relative sensitivity and birefringence of the recommended structure are 57.61% and 7.53 × 10^− 3 respectively at 1.33 μm wavelength on the absorption line of toxic gasses (methane and hydrogen fluoride). The exhibited beam divergence is about 4.1° at the same wavelength. Besides, beat length, nonlinear coefficient, effective area and V parameters are also described briefly for optimized S-PCF structure over broader wavelength range from 1 μm to 1.8 μm.