Rapid detection of multiple gas mixtures and evaluation of harmful gas removal efficiency in a deck decompression chamber using dynamic switching mass spectrometry

Abstract

The multiple gas mixtures in the deck decompression chamber (DDC) serve as a life-sustaining medium for divers to adapt to high-pressure environments and to safely decompress after saturation diving operations. However, due to the complexity of the gas composition and the wide concentration range, there is currently no technique that can rapidly detect all gases in the DDC. In this study, we developed a photoinduced chemical ionization (pCI) and electron impact (EI) dynamic switching mass spectrometry system. This technique was applied to investigate the spatial distribution uniformity of respiratory gases within the DDC at pressures of 0.13 MPa, 0.6 MPa, and 1.5 MPa, as well as the removal efficiency of toxic gases at 1.5 MPa. The switching stability time of pCI/EI dynamic switching mass spectrometry was 30 s per cycle, with optimal detection performance metrics including a detection limit down to 0.58 ppb (H₂S), a fastest response time of 2 s (for CO₂ and H₂S), sensitivity up to 62.97 counts per ppb (H₂S), and an overall concentration detection range spanning from 1.0 × 10⁻⁹ v/v (1 ppb) to 4.5 × 10⁻¹ v/v (45%), covering the requirements for all target gases. At the three pressure levels, the spatial distribution uniformity of O₂ in the DDC was 0.34%, 0.21%, and 0.08%, with the time to reach uniform distribution being 5 min, 3 min, and 1 min, respectively. For CO₂, the spatial distribution uniformity was 0.62%, 1.61%, and 1.30%, with uniform distribution achieved in 10 min, 7 min, and 5 min, respectively. The removal efficiencies for harmful gases such as CO₂, CH₄, NH₃, and H₂S were 39.57%, 10.75%, 14.29%, and 3.96%, respectively. Under high-pressure conditions, O₂ and CO₂ rapidly achieved uniform distribution within the DDC. The pCI/EI dynamic switching mass spectrometry technology provides a rapid detection method for multicomponent gases in enclosed chambers like the DDC. This technology holds significant implications for the life support and operational efficiency of personnel involved in shipwreck salvage, underwater construction, and deep-sea exploration of marine resources.