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A Brief Overview of How Do Hand Dryers Work

How do Hand Dryers Work
You must have used hand dryers installed in washrooms at public places. Ever wondered how they work? Go through this post to know about it.
Priyanka Kosta Sonkushre
Last Updated: Mar 26, 2018
The basic utility of a hand dryer is to dry hands using an electric source. Hand hygiene is a very important aspect in preventing spread of communicable diseases. A washroom is a place where the presence of disease-causing microorganisms is very high as compared to other places. And if a washroom is meant for public use, then one can imagine the concentration of microorganisms in there. Since many disease-causing germs spread through touch, hand dryers were devised so that people can dry their hands without actually touching the roll of paper towel available for common use in public restrooms. Hand drying machines not only help in maintaining hygiene, but also help in reducing waste produced by the use of paper towels. Very often we use this machine in public restrooms or at home without actually knowing how it works. So, let's see how a hand drying machine works.
Working of a Hand Dryer
Electricity consumption for regular hand dryers is around 2200 watts, and for energy-saving devices it is around 1600 watts. Earlier, these devices were switched on using a button. When the button was pressed, the device started blowing warm air for drying hands. But new-age hand dryers have infrared motion sensors installed in them. The device detects motion and automatically turns on when hands are placed for drying.
Similarly, it automatically turns off when hands are moved away from the dryer, thereby preventing wastage of electricity.
Heating and Drying
Hand below hand dryer
Warm air is produced by a hand dryer using a heating coil made up of Nichrome, a hybrid of chromium and nickel. When air, having a temperature as that of the surrounding environment, is passed through the heating element, it gets warm. The heating coil is usually heated 50 degrees higher than the existing room temperature. The warm air is then blown out of the device through a tube or a vent facing downwards. Hands are placed in the path of warm air coming out of hand dryer for drying.
The warmth and pressure of air coming out of the dryer is sufficient to evaporate water from wet hands. First, the air pressure blows off water droplets from the hands and then the warmth dries out the moisture from the hands. Traditional hand dryers need around 45 seconds to dry hands, whereas new-age dryers take around 15 seconds to do this task.
High speed hand dryer
There has always been a debate about the level of hygiene maintained by hand dryers. The cause of concern was that these devices circulate same air again and again, thereby making no difference in terms of hygiene. This was definitely true in case of hand dryers used in earlier times, but with new innovations coming up, manufacturers have tackled this issue by making use of High Efficiency Particulate Air (HEPA) filters in their devices.
These filters are 99.97% efficient in removing particles of 0.3 microns in size or smaller, from air used for drying hands. Thus, the amount of disease-causing germs in air blown out of the dryer is substantially reduced. Some manufacturers have even made it possible for air to be released at a speed of 400 mph which helps in sterilizing it before being released in the atmosphere.
A hand dryer is a one-time investment which can serve its purpose for a long duration of time. Regular cleaning of the dryer is essential to maintain its efficiency. Janitors in charge of cleaning hand dryers must ensure that the air passage of the device is clean to maintain a steady flow of air. The sensor used to detect hand-motion must also be cleaned regularly so that its sensing ability is maintained at its best. Only when these few things are followed, working of a hand dryer will not be hampered.