Hand sanitizers with less than 60% ethyl or isopropyl alcohol are not effective.

To kill Staph aureus, the bacteria responsible for MRSA (methicillin resistant staph aureus) infections, you must use a sanitizer with at least 62% alcohol.

Use a hand gel with between 62% and 95% ethyl alcohol (higher than 95% alcohol might be less effective).

Rub it vigorously into your hands, including in between your fingers and along your nails, until the gel has dried.

Use enough gel to keep rubbing so that there is moisture for at least 20 seconds before the product dries completely. If the alcohol evaporates to fast, bacteria will not be killed

Common situations to use a hand sanitizer:

BEFORE:
eating, drinking or touching food and beverage products
handling an infant or child
touching items that may come in contact with food, eyes, nose or mouth
touching your own eyes, nose or mouth
sexual contact

AFTER:
sneezing, blowing your nose, or coughing
hand rails for stairs or public transportation
using shopping carts
going to the gym
using public computers, telephones, or ATMs
handling a baby diaper or toys
playing with small children or attending places such as parks and jungle gyms
coming in contact with animals and pets
you touch something wet and suspicious

See also ...
Purell  -- purell.com