A method for analyzing a gas, in order to estimate an amount ( c k ) of a plurality of different gaseous species ( G k ), called the candidate gaseous species, potentially present in the gas, each candidate gaseous species being able to absorb light radiation in an absorption spectral band (Δ x ), the method comprising the following steps: a) placing the gas between a light source and a light sensor , the light source being able to emit illuminating radiation that propagates through the gas, the light sensor being able to detect radiation transmitted by the gas and to deliver a detection signal representative of an intensity ( I j ) of the detected radiation; b) illuminating the gas ( G ) using the light source , the radiation illuminating the gas having an illumination spectrum ( S j ), the illumination spectrum extending continuously in a spectral band, called the illumination spectral band (Δ 12 ), covering the absorption spectral band (Δ x ) of a plurality of candidate gaseous species; c) during the illuminating step, detecting, with the light sensor , a radiation transmitted by said gas; d) reiterating steps b) and c), while adjusting the light source such that, in each step b), the illumination spectrum ( S j ) is modified; e) estimating an amount ( c k ) of each of the candidate gaseous species depending on the intensities ( I j ) of the radiation detected in each step c), respectively, each intensity ( I j ) being associated with one illumination spectrum ( S j ); wherein : in each step c), the radiation transmitted by the gas is detected in at least a same detection spectral band (Δ 20 ), extending continuously between a minimum wavelength ( λ 20-min ) and a maximum wavelength ( λ 20 -max ) , with a spectral width of at least 1 μm, and covering absorption spectral bands (Δ x ) of a plurality of candidate gaseous species ; and in each iteration of steps b) and c), the illumination spectrum ( S j ), extending continuously in the illumination spectral band, is modified within the same illumination spectral band (Δ 12 ). a) placing the gas between a light source and a light sensor , the light source being able to emit illuminating radiation that propagates through the gas, the light sensor being able to detect radiation transmitted by the gas and to deliver a detection signal representative of an intensity ( I j ) of the detected radiation; b) illuminating the gas ( G ) using the light source , the radiation illuminating the gas having an illumination spectrum ( S j ), the illumination spectrum extending continuously in a spectral band, called the illumination spectral band (Δ 12 ), covering the absorption spectral band (Δ x ) of a plurality of candidate gaseous species; c) during the illuminating step, detecting, with the light sensor , a radiation transmitted by said gas; d) reiterating steps b) and c), while adjusting the light source such that, in each step b), the illumination spectrum ( S j ) is modified; e) estimating an amount ( c k ) of each of the candidate gaseous species depending on the intensities ( I j ) of the radiation detected in each step c), respectively, each intensity ( I j ) being associated with one illumination spectrum ( S j ); in each step c), the radiation transmitted by the gas is detected in at least a same detection spectral band (Δ 20 ), extending continuously between a minimum wavelength ( λ 20-min ) and a maximum wavelength ( λ 20 -max ) , with a spectral width of at least 1 μm, and covering absorption spectral bands (Δ x ) of a plurality of candidate gaseous species ; and in each iteration of steps b) and c), the illumination spectrum ( S j ), extending continuously in the illumination spectral band, is modified within the same illumination spectral band (Δ 12 ). <EOS>