During periods of increased risk relating to a specific pathogen during an epidemic, or after diving in an area known as a high risk for a specific pathogen, disinfection procedures will target that pathogen.
During an epidemic, the first line of defence is for symptomatic people and people who have tested positive for the infection to refrain from diving, however in the early stages of some diseases it will not be apparent that the person is infectious, so it is prudent to take reasonably practicable preventative measures when the risk is assessed as significant.
Disinfection to prevent SARS-CoV-2 infection
| This section needs to be updated. (December 2022) |
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the COVID-19 disease is considered easier to kill than the closely related SARS-CoV-1, so in the absence of specific test results for SARS-CoV-2, methods for disinfection of SARS-CoV-1 are assumed to be effective.[6]
According to the World Health Organization, SARS-CoV-1 loses infectivity after 15 minutes at 56 °C (133 °F), Another study showed that SARS-CoV-1 remains stable between 4 °C (39 °F) and 37 °C (99 °F), and loses infectivity after 30 minutes at 56 °C (133 °F). (Duan et al 2003 in DANSA 2020)[7]
Divers Alert Network has estimated that a breathing air compressor in a 27 °C (81 °F) environment, would have an inter-stage temperature inside the cylinder of about 107 °C (225 °F). The calculation does not account for anything outside of nominal conditions, but it indicates the instantaneous temperature at the moment of peak pressure. In reality the compressed air is cooled between stages, and the compressor itself is fairly hot, so direct measurement would be relatively simple, but this does not take into account time of exposure to temperature.[7]
The actual gas temperature at the outlet from each stage was reported to be around 66 °C (151 °F) This is considered to be hot enough to kill SARS-CoV-2, so it is considered unlikely that the virus would survive passing through a compressor. Infected droplets exhaled by a person can be as small as 0.5 micron, so the compressor particle filter systems would not reliably remove them.[7]
There are many disinfectants that are assumed to be effective on SARS-CoV-2 based on their effectiveness on similar viruses which are considered more resistant to deactivation.[6] The United States Environmental Protection Agency (EPA) publish a list of disinfectant products which meet the EPA's criteria for use against SARS-CoV-2 in "List N: Disinfectants for Use Against SARS-CoV-2" in the absence of specific testing on SARS-CoV-2.[8]
Divers Alert Network have recommended following Centers for Disease Control (CDC) advice on using a solution of household bleach diluted 4:100 in water with a contact time of 1 minute followed by a thorough rinse in water to remove residual disinfectant.[1] As of April 24 2020, Steramine, a quaternary ammonium compound popular for disinfecting diving equipment, did not appear on the EPA's "List N" and is therefore not endorsed for disinfecting SARS-CoV-2. However, many other products using quaternary ammonium compounds are on List N.[8] Quaternary ammonium-containing products are harmful to the environment and suitable precautions should be applied to their use and disposal.[7]
Sodium hypochlorite bleach is a strong oxidant which has been tested in different concentrations, and is proven to be effective against viruses by damaging the viral genome. The World Health Organization (WHO) recommend a 1:100 dilution of 5% sodium hypochlorite bleach solution for general disinfection, which yields 0.05% or 50 ppm of the active ingredient which requires a soaking time of 30 minutes or at least 10 minutes wet time if sprayed onto a nonporous surface. Specific studies on SARS-CoV-2 found that a sodium hypochlorite bleach concentration of 0.1% (1,000 ppm) was necessary to adequately reduce infectivity when sprayed onto a non-porous surface, and that it would inactivate the virus within 1 minute. A study on SARS-CoV-1 showed that a 1:100 dilution (0.05%) inactivated the virus after an immersion of 5 minutes.[7] Bleach-based disinfectants may cause accelerated degradation of some materials used in breathing apparatus components.[9]
Pathogens associated with specific environments
Commercial diving operations are often required for maintenance and repair work in water known to have high counts of E. coli and other pathogens. Diving equipment used in these environments should preferably isolate the diver completely from the environment, and the diver and equipment should be decontaminated by competent persons after leaving the water and before removing the encapsulating equipment from the diver.[5]
Caves are isolated ecosystems known contain unique, protected, or endangered species and are susceptible to cross-contamination from foreign species of plants, animals, and micro-organisms from other bodies of water. For example, the National Park Service requires certification of heat and chemical disinfection followed by a prolonged 30-day drying before entering Devils Hole.[10]