Human subjects are a prime source of microbial contamination of the diving gear and the interior of deep-water diving complexes (DWDC). Disinfecting measures cannot ensure infectious safety of deep-water dives. Investigations in vitro were to compare effectiveness of a standard and a novel detergent against the microorganisms isolated from DWDC-250 at SRC-IBMP. It was discovered that 21% of microbial strains were resistant to the standard 3% solution of hydrogen peroxide. Diluted in ratio 1:10, polycept Demos (alkyl dimethyl benzyl ammonium chloride AB 0.5%) demonstrated 100% effectiveness in usual conditions and in hyperbaric experiments with various gaseous mixtures. Biocide Demos should be further tested during simulation of dives in DWDC-250.