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Qubit coherence is a crucial requirement for realizing fault-tolerant quantum computation. In superconducting qubits, coherence times are typically shorter than those of other physical qubit platforms, primarily because their macroscopic size leads to stronger coupling to environmental noise. A significant source of decoherence arises from quasiparticles generated by infrared (IR) radiation. These quasiparticles act as dissipative excitations, providing an additional loss channel for the qubit. In this talk, we present our approach to characterizing and mitigating quasiparticle effects in superconducting qubits. We have developed a comprehensive IR shielding and filtering scheme, incorporating indium seals that play a crucial role in blocking IR leakage through packaging gaps. With these improvements, qubit coherence is significantly enhanced. Notably, when the qubit package and all shielding stages are thoroughly thermally anchored to the mixing plate, we achieve an effective qubit temperature as low as 17 mK, which, to the best of our knowledge, is the lowest value reported to date.