52 States in 8 Months

Help, Germs everywhere!

Posted in University stuff by Ulf on June 14, 2009

The swine flu is a great opportunity to frighten people about nature. The newest example can be found in our restrooms:

So, remember the proper hand washing techniques:

  1. Use hot water and soap.
  2. Scrub hands for 20 seconds.
  3. Clean under fingernails.
  4. Rinse thoroughly.
  5. Turn faucet off with paper towel.

Got it? We got a course on hand-washing at a University! I still can’t believe it. Of course nobody obeys it, especially the last point. What I believe we should tell people is that they should dry their hands with those paper towels instead of using electric hand dryers if they really want to clean them. The air flow of the hand dryer does remove the water, yes. But drying your hands with a towel is some sort of mechanical cleaning, so it will remove the water and whatever else is on top of your skin.

Just for taking a picture, I really turned off the faucet with a towel. And I even opened the door with a towel:

bild9746 bild9747

The Smithsonian Institution abolished paper towels in an effort to help the environment. Since I know about that I wanted to do the following calculation:

Recently I found some numbers on carbon dioxide emissions of power plants. I ended up calculating with about 700g CO2/kWh. Most hand dryers heat up the air instead of simply accelerating it. They use about 2kW of energy for about 45 seconds which is 0.025 kWh or about 18g of CO2 emissions. This results from wasting about 5g of carbon. That should be roughly the worst case for an electric hand dryer.

According to Wikipedia tissue paper has a weight of about 20g/m2. The surface is not even and there are usually two layers, so let’s calculate with 50 g/m2. I believe that I use about 0.05 m^2 of paper towel for drying my hands, so that’s about 2.5g. Not all of that is carbon, but I still believe that with the additional CO2 expenses during production and transportation, paper towels are probably worse than electric hand dryers. Especially than those hand dryers that just use a strong air flow instead of heating it.

(However, paper towels are made from sustainable resources. That might change my mind again.)

3 Responses

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  1. steffi said, on June 14, 2009 at 1:37 pm

    Oh no! In the Hamilton there are ONLY elctrical hand dryers. Should I take a towel to work? Should I dry my hands with my cloths or shouldn’t I wash my hands at all?

  2. Andreas said, on June 14, 2009 at 2:54 pm

    der eigentlich wichtige Teil beim Händewaschen ist tatsächlich das Abreiben der Bakterien mit dem Handtuch nachdem sie vom Wasser etwas von der Haus gelöst wurden.
    Daher ist aus hygienischen Gründen ein Einweg-Papierhandtuch die beste Lösung (und meinetwegen auch aus chlorfrei gebleichtem Altpapier)

  3. Ulf said, on June 16, 2009 at 10:18 am

    Steffi: I like the proposal of taking a towel to work or using clothing!
    That would both minimize the material costs and at the same time allow mechanical cleaning.

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