What is the standard dilution of bleach used for disinfection?

• A. One part chlorine to ten parts water
• B. One part chlorine to one part water
• C. Ten parts chlorine to one part water
• D. One part chlorine to hundred parts water

Answer: (A)

Bleach disinfection is most reliably achieved by diluting the product to a moderate strength that is still effective against many pathogens but less harsh on surfaces. When household bleach (about 5% sodium hypochlorite) is mixed as one part bleach to ten parts water, the active chlorine level becomes around 0.5%, which is a common disinfecting concentration for general cleaning. This dilution provides a practical balance: it is strong enough to inactivate a wide range of bacteria and viruses on nonporous surfaces while reducing the risk of corrosion, fumes, and residue that come with stronger mixes. For best results, use fresh solution, keep the surface wet for the recommended contact time, and follow label directions, including not mixing with ammonia or acids.