How Effective is Hand Sanitizer?

By Evia Loewen
Elementary (Grades 4-6)
Experiment | Biology

Bacteria are everywhere! The goal of this experiment was to determine how effective hand-sanitizer was at killing bacteria on two different commonly used door handles at school.

This is of great importance because although many bacteria are essential, there are some bacteria that can be harmful and cause infections and illness. The purpose of this experiment is to prove that disinfection is important to keeping us healthy. My experiment asks the question: how effective is hand-sanitizer after touching a dirty door handle?

The front door handle and girls bathroom door handle were used as test sites. Bacteria from a hand that touched these sites were cultured in nutrient-rich agar petri dishes with and without the application of 70% ethyl alcohol-based hand-sanitizer. After 7 days, bacterial cultures were counted in 9 dishes (control plus 8 test dishes).

The results of the experiment were as follows: the hand that touched the front entrance door handle without hand-sanitizer had 195 colonies, and with hand-sanitizer had 18 colonies on average. This amounted to a 91% reduction in bacterial colonies. The hand that touched the girl’s bathroom door handle without hand-sanitizer had 34 colonies, and with hand-sanitizer had only 24.5 colonies on average. This amounted to a 28% reduction in bacterial colonies. In conclusion, it was found that there were more bacterial colonies on the hand that touched the front entrance door handle than the girl’s bathroom door handle, both with a significant reduction after the application of hand-sanitizer as hypothesized.

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