For alcohol to be effective, its concentration must be at least what percentage?

• A. 70% or Higher
• B. 50% or Higher
• C. 90% or Higher
• D. 30% or Higher

Answer: (A)

Alcohol to be effective relies on having enough water in the solution. Water helps the alcohol denature proteins and disrupt microbial membranes. When the concentration is around 70% or higher, there’s enough water present to allow these processes to occur and the liquid stays in contact long enough before it evaporates. If the concentration is too low, it won’t reliably kill microbes; if it’s very high, it evaporates too quickly and doesn’t penetrate or contact surfaces long enough. So the minimum concentration generally considered effective is about 70% or higher.