In this article, industry manufacturers answer common questions asked by members of the industry

Does the air being blown out of hand dryers have to be warm in order to properly dry hands and kill bacteria?
The warm dry air creates a hostile environment for most pathogens. The warmer air dries hands more quickly with greater customer satisfaction in many applications. As an option, the heating element can be removed to increase energy efficiency and eliminate the need for dedicated electrical line. This reduces installation and operating costs. Drying time is only increased by 2 to 3 seconds.

— Michael E. Robert, vice president sales and technology, American Dryer Inc., Livonia, Mich.


Proper hand washing hygiene continues to be the most important component in killing bacteria. Doctors at the University of Ottawa have proposed that "the blowing of warm air may lead to an accelerated dehydration of the skin surface, thereby affecting the viability" of the microorganism. Moreover, the warm air may "penetrate all the crevices in the skin, whereas absorbent towels may not reach such areas, even though the skin appears dry" (Ansari et al 248). Hand Dryers are so effective that researchers Meers and Leong have declared that there is "no bacteriological reason to exclude them from the clinical areas" (171). In a published white paper on high speed hand drying, phase 2 is described as the evaporation phase in the drying process whereby evaporation occurs from a heated air stream drying the ‘residual moisture layer’ on a user hands. A heated air stream is needed to accomplish this.
— William Gagnon, vice president of marketing and key accounts, Excel Dryer, East Longmeadow, Mass.


No hand drying method kills bacteria. A HEPA filter is the best way for capturing 99.97 percent of bacteria. Warm air hand dryers use 60-year-old technology and rely on evaporation to dry hands. This is slow and uses large amounts of electricity. Our hand dryer uses high-speed sheets of unheated air to dry your hands quickly and as hygienically as paper towels while creating 70 percent less carbon emissions. And without the potential for other hazards such as overflowing bins and clogged toilets.
— Rob Green, engineer, Dyson, Chicago


The air being blown out at high speed helps push and dry the moisture off the hands. The heating of the air is not meant to be a bacteria killer/eliminator. There is no study that indicates that the temperature of the hand dryer air has anything to do with killing bacteria.
— Kevin Knapp, director of sales and marketing, Palmer Fixture, Green Bay, Wis.


No. It is in the technique of washing and drying completely that supports better hygiene.
— Dan Storto, senior vice president, sales and marketing, World Dryer, Berkeley, Ill.


Are HEPA filters necessary for hand dryers?
HEPA filtration better meets the needs of specialty markets such as healthcare and food processing, but is not imperative for markets with fewer regulatory and compliance guidelines.
— William Gagnon, vice president of marketing and key accounts, Excel Dryer, East Longmeadow, Mass.


Yes. HEPA filters remove 99.97 percent of bacteria from the air so the hands are dried using cleaner, not dirty air. Other hand dryers do not come standard with HEPA filters, and most do not use any filter. And if they do, these filters are made from simple gauze or foam. This means they do not remove a significant proportion of bacteria as gaps in the filter are many times greater than bacteria so they pass straight through.
— Rob Green, engineer, Dyson, Chicago


Not in our opinion. HEPA filters are not effective in hand dryers because they only filter a small part of the air going through the dryer. This is because the filtered air coming out of the nozzle draws in and mixes with the unfiltered air. This principal is known as the Venturi effect.

The result is that less than 10 percent of the air reaching the users hands is filtered. HEPA filters are expensive and must be replaced regularly or the dryer will lose power or fail. The air in the washroom is the same air that you breathe. If one wants to clean that air, a commercial air filter unit is required that filters all of the air in the restroom 4 to 6 times per hour.
— Michael E. Robert, vice president sales and technology, American Dryer Inc., Livonia, Mich.


They are an added benefit to the customer who perceives that bacteria is transmitted during the drying process. Some might suggest that the clean air from the nozzle is the important part, but it is what the air is being drawn through that matters. The air is the same in which the user has walked and this is not filtered air.  Therefore, the HEPA filter eliminates any potential airborne bacteria providing for a clean hand dry for the customer.  
— Kevin Knapp, director of sales and marketing, Palmer Fixture, Green Bay, Wis.


The use of HEPA filters has been touted by some in the hand dryer industry as more hygienic, however the benefits of a HEPA filter in hand drying have not been established and supported by independent scientific research.

On the contrary, the Mayo Clinic study of all hand drying methodology determined that all means of hand drying were generally equally effective in controlling residual bacteria or micro-organisms after hand drying. The Mayo Clinic study concluded that if anything, warm air hand dryers had a slightly reduced rate of residual bacteria and micro-organisms after hand drying than other commonly used hand drying methods.

At this time, the use of HEPA filters in hand dryers has been more of a marketing strategy for product differentiation than as a proven method of improving hand hygiene.
— Dan Storto, senior vice president, sales and marketing, World Dryer, Berkeley, Ill.




POSTED ON: 5/14/2012