Hand Dryer - Hygiene

Hygiene

In 2008 a published study was conducted by the University of Westminster, London, to compare the levels of hygiene offered by paper towels, warm air hand dryers and the more modern jet-air hand dryers. The key findings were:

• after washing and drying hands with the warm air dryer, the total number of bacteria was found to increase on average on the finger pads by 194% and on the palms by 254%
• drying with the jet air dryer resulted in an increase on average of the total number of bacteria on the finger pads by 42% and on the palms by 15%
• after washing and drying hands with a paper towel, the total number of bacteria was reduced on average on the finger pads by up to 76% and on the palms by up to 77%.

The scientists also carried out tests to establish whether there was the potential for cross contamination of other washroom users and the washroom environment as a result of each type of drying method. They found that:

• the jet air dryer, which blows air out of the unit at claimed speeds of 400 mph (≈640 km/h), was capable of blowing micro-organisms from the hands and the unit and potentially contaminating other washroom users and the washroom environment up to 2 metres away
• use of a warm air hand dryer spread micro-organisms up to 0.25 metres from the dryer
• paper towels showed no significant spread of micro-organisms.

In 2005, in a study conducted by TÜV Produkt und Umwelt, different hand drying methods were evaluated. The following changes in the bacterial count after drying the hands were observed:

Another paper found that air dryers dispersed marker bacteria in a radius of three feet (one metre) and onto the investigator's laboratory coat. Another study found that hot air dryers had the capacity to increase the bacterial count on the skin, and that paper towel drying decreased skin bacterial count. This is corroborated by another study which found that the mechanical action of paper towel drying removed bacteria, something air dryers cannot do.

Doctors at the University of Ottawa claim that "the blowing of warm air may lead to an accelerated dehydration of the skin surface, thereby affecting the viability" of the microorganisms, and that the warm air may "penetrate all the crevices in the skin, whereas absorbent towels may not reach such areas, even though the skin appears dryer".

The European Tissue Symposium, a trade body, has produced a position statement on the hygiene standards of different hand drying systems. This summarises some of the scientific research undertaken.

A lot of hand dryers such as also contain carbon and microbe filters which also stop the spread of infection and increase hygiene.

Some modern hand dryers contain a drip tray at the bottom of the unit. If used properly avoids water streaks and hygiene, but requires regular emptying and cleaning.