Investigations into infrared radiation transmission of periodic subwavelength Pd hole arrays reveal a transmittance attenuation of the main resonant peak upon exposure to hydrogen of the hole arrays. The attenuation is attributed to the formation of Pd hydride, which results in the combine effects of lattice expansion of the Pd film, generating a decrease in the hole width, and optical properties variations of the Pd film, giving rise to stronger damping of the surface plasmons. The reduction in the hole width of the arrays is estimated to be of the order of a few tens of nanometers. Our results illustrate the possibility of detecting minute changes in the structure of the metallic hole arrays by monitoring the transmittance of the resonant peaks. The all-optical hydrogen sensing scheme presented in this work is thought to find applications in the detection of hydrogen at concentration levels near the lower flammability threshold for alarm purposes.