BIOLOGICAL DECONTAMINATION

The most common methods used in biological decontamination are flushing, scrubbing, and heating. Sterilizing gases and disinfectant vapors are used in industrial decontamination, but they are not currently recommended for shipboard use. The method to be used in any particular case depends upon the nature of the area or equipment to be decontaminated.

Water Washdown

For the ship's exterior surfaces, the water washdown system (together with hosing down) will be the most effective countermeasure. After washdown and hosing, thorough scrubbing or swabbing with approved compounds will decontaminate any remaining biological agents.

Use the following procedures to hose down surfaces that have biological contamination.

1. Be sure the firemain pressure is at least 80 psi.

2. Work from top to bottom, from the windward side to lee side, and from forward to aft.

3. Hold the hose at a 30- to 40-degree angle so that the water will hit the deck 15 to 20 feet away from the nozzle. Use a solid stream.

4. Overlap the hosed areas to provide a complete washdown.

5. Control the drain-off to be sure it does not run into the ship.

Scrubbing

Use liquid disinfectants or decontaminants to decontaminate the ship's interior spaces. However, it is difficult to reach all contaminated surfaces to ensure that the liquid contacts the organisms. To overcome this problem, try to apply liquid disinfectants or decontaminants to all surfaces with a coarse spray device or with swabs until the surfaces are completely wet. Then rub or scrub all accessible surfaces with swabs or brushes to bring the organisms and the liquid into close contact. After this treatment, close the compartment for a prescribed period. Operating personnel should be equipped with masks and protective clothing as protection against the decontaminant as well as against the organisms.

Several liquid decontaminants have proved to be effective against biological agents. However, the only one generally available for shipboard use is calcium hypochlorite. It should be used in a 1 percent solution for general immediate decontamination and a 9 percent solution for heavily contaminated areas. (NOTE: Calcium hypochlorite and oil form an explosive hazard. Be careful when it is used. ) This solution is more effective if a 0.5 percent detergent called decontaminating compound is added. If decontaminating compound is not available, you can substitute laundry detergents in the same percentages. If calcium hypochlorite is not available, you can substitute laundry detergents, soaps, dishwashing compounds, or boiler compound.

Calcium hypochlorite is a powerful oxidizing agent, and it is highly corrosive. The corrosiveness increases as the temperature goes up. Therefore, calcium hypochlorite should not be used to decontaminate sensitive electrical or electronic equipment on aircraft, weapons materials, navigation instruments, or similar equipment. This is especially true where steam is used.

In using calcium hypochlorite or other cleaning agents for biological decontamination, start at the highest point and work downward. Change the wiping cloths, waste, swabs, and scrub brushes at frequent intervals.

Steaming

Steaming is an effective method of decontamination for the ship's interior spaces. Admit enough steam to the compartment so that all air will be displaced. The compartment surfaces will then heat rapidly to the maximum temperature of approximately 212F. At this temperature, most germs are killed in about 15 minutes.