Hand dryer

A push-button hand dryer.

Hand dryers are electric devices found in public washrooms that are used to dry hands. They may either operate with a button or automatically using an infrared sensor.

Costs

Hand dryers have been popular with industries for their apparent economies. According to manufacturers, hand dryers can cut costs by as much as 99.5% (for example a company may spend $2340.00 per year on paper towels, where as the hand dryer expenditure would be as low as $14.00 per year - this will vary according to the cost of paper towels and electricity). They require very little maintenance compared to paper towels, which must be replaced. An added benefit is the removal of the paper waste. Hand dryers represent a larger initial investment, so those responsible for facility management must do a careful cost analysis to determine whether they are cost effective in their building. Costs are always relative to the KW/h cost that the facility is charged by its provider. In the UK, this will typically be around 10-12p, the only way to compare costs accurately is to work out the rated energy consumption and divide it by the number of drys the hand dryer is capable of performing back to back in 1 hour, this will give the energy consumption per dry. The world's lowest energy hand dryer uses just 1 watt-hour per dry and is rated at 0.24 kW.

Environment

Newer models of hand dryer are faster, quieter and more efficient.

Due to the reduction in litter and waste in comparison with paper towels, which cannot be recycled,^[1] hand dryers are also claimed to be better for the environment. Another study shows that whereas the majority of the environmental impact of a hand dryer occurs during its use, the environmental impact of paper towels is predominantly in the material production and manufacturing stages.^[2] It is estimated that hand dryers use 5% less energy than paper towels in the first year, and 20% less over five years.^[3] A World Dryer study of 102 hand dryers installed in public schools in Topeka, Kansas, claimed an annual savings of 34.5 tons of solid waste, 690,000 gallons of water,and 587 trees; another World Dryer study of 153 hand dryers in the Iowa state capitol showed an annual savings of 10.5 tons of solid waste and 176 trees.^[3]

However, a Dutch study published in March 1995 indicated that there was environmental parity between hand dryers and paper towels as hand drying methods when all factors were taken into consideration.^[4]

Hygiene

In 2008 a published study was conducted by the University of Westminster to compare the levels of hygiene offered by paper towels, warm air hand dryers and the more modern jet-air hand dryers.^[5] It found that 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%; and 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%.^[5]

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.^[6] 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.^[7] 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.^[8] This is corroborated by another study which found that the mechanical action of paper towel drying removed bacteria, something air dryers cannot do.^[9]

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".^[10]

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.^[11]

Dyson (The creators of the Airblade Jet Air dryer) have countered the claims presented suggesting that the results were intentionally falsified. ^[12]

Reception

Research conducted in 2008 indicated that European consumers much prefer hand towels over hand dryers in public washrooms. 63% of respondents said paper towels were their preferred drying method, while just 28% preferred a hand dryer. Respondents overwhelmingly considered paper towels to offer faster hand drying than electric hand dryers (68% vs 14%). On the whole they also considered paper towels to be the most hygienic form of hand drying in public washrooms (53% vs 44%).^[13]

Developments

The earliest hand dryer was patented in 1921 by R.B. Hibbard, D. J. Watrous and J.G. Bassett for the Airdry Corporation of Groton New York.^[14] This machine was sold as a built in model or freestanding floor unit that consisted of an inverted blower (much like a handheld blow dryer) that was controlled by a floor pedal. Known as "Airdry The Electric Towel", these units were used in restrooms, barbershops and factories. Airdry Corporation moved to Chicago and San Francisco in 1924 to centralize their distribution.^[15]

The hand dryer was later popularized in 1948 by George Clemens.^[16] In 1993, Mitsubishi Electric introduced a new type of hand dryer that blows jets of air on both sides of the hand, pushing the water off rather than evaporating it.^[17]

Hand Dryer Sound

Many people object to the noise created by the modern hand dryers. A recent paper ^[18] showed that the typically installed hand dryer creates over 80 dBA of noise, and that the manufacturers' reported sound intensity levels as measured in the lab are often exceeded in typical installations.

See also

• Towel
• Paper towel

References

Wikimedia Commons has media related to Hand dryers.