Microbiological monitoring of scuba cylinders under routine filling and seasonal diving conditions

Introduction: The aim of this study was to monitor the microbiological status of the inner surfaces of scuba cylinders under routine air filling conditions and to assess whether microbiological contamination emerges or persists over time. Methods: A prospective longitudinal microbiological study was conducted using two complementary sampling models. Serial sampling of a steel scuba cylinder and its associated compressor air filter was performed at three-day intervals over 45 days. To assess reproducibility under operational conditions, additional microbiological sampling was performed from 27 scuba cylinders actively used during the diving season. Samples were analysed using standard culture methods. Results: No microbial growth was detected in bacterial cultures obtained from any of the cylinder inner surface or compressor air filter samples throughout the 45-day monitoring period. No temporal changes or cumulative contamination trends were observed. Similarly, no microbial growth was detected in cultures obtained from the additional 27 scuba cylinders sampled during the active diving season. Conclusions: Under routine operating conditions with standard maintenance and air filtration practices, the internal environment of scuba cylinders may remain microbiologically stable over time, suggesting a low risk of microbiological contamination in properly maintained compressed air systems.