Strength and Quantity of Hypochlorite Solutions: How Much Is Enough?

Special Pathogens Branch recommends a 10% bleach solution be used to inactivate hantaviruses.   A 10% solution corresponds to 1 and a half cups of household bleach per gallon of water, or 1 part bleach to nine parts water.

Why a 10% solution?  Household bleach is made of 5.25% Sodium Hypochlorite (52,500 ppm); therefore, a 1% bleach solution is 525 ppm. Some experiments have shown that 200 ppm (or even less in some experiments) will inactivate most viruses. Therefore it would seem that a 1% solution of household bleach might be adequate. However, hypochlorite is substantially and quickly inactivated in the presence of organic matter. So, although 1% may be adequate for surface decontamination, a 10% dilution may be a better choice for inactivation of virus when one is cleaning out areas which have been infested by rodents. This 10% concentration is currently supported in CDC Infection Control recommendations.

Amount of Hypochlorite Solution

No matter what concentration of solution is used, only the outside layer of the material to be disinfected is bound with the chlorine molecules in the bleach solution, unless the object is entirely soaked through. Complete soaking is more easily achieved when greater quantities of water are used. Therefore, it is recommended that the material being sprayed or poured over be thoroughly drenched, in order to maximize penetration of the material.

References

Boyce JM, Pittet D. Guideline for Hand Hygiene in Health-Care Settings, 2002. MMWR, 2002;51(RR16);1-44. Available online at CDC.

Favero MS, Bond WW. Sterilization, disinfection, and antisepsis in the hospital. 1991. In: Manual of Clinical Microbiology, American Society for Microbiology. Washington, D.C. Chapter 24: 183-200.

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This page last reviewed Thursday, August 5, 2004

Special Pathogens Branch
Division of Viral and Rickettsial Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
U.S. Department of Health and Human Services