How do hand dryers work?

Warm-air hand dryers remove surface moisture from the skin by a combination of evaporation and physical action.

A conventional hand dryer uses a fan to draw ambient air from the room, and a heating element to raise the temperature of the air. The fan exhausts the air, through a nozzle, over the user’s hands.

The natural process of evaporation is greatly accelerated by the warmth and the velocity of the exhaust air. Rubbing the hands together in the air stream also helps to break up and vaporize the water molecules.

High-speed hand dryers use a different type of fan to accelerate the air to very high velocities. Although heat also plays a role, the high-speed dryer relies more on the physical pressure of the air to blow water off the hands and to vaporize the residual moisture.

How much electricity does a hand dryer use?

Hand dryer electrical consumption is measured in watts. Most dryers consume between 1200 watts (1.2 kW) and 2500 watts (2.5 kW) while in operation, and less than 1 watt while at rest. To determine electricity use, however, we must multiply the consumption by the amount of time in operation.

The Comac ONE, for example, consumes 1.45 kW and takes approximately 30 seconds to dry the hands. The electricity use per hand dry is therefore equal to 43.5 kW-seconds, or 0.012 kWh (kilowatt-hours).

The high-speed Comac BLAST also consumes 1.45 kW but takes only approximately 10 seconds to dry the hands. The electricity use per hand dry is therefore equal to 14.5 kW-seconds, or 0.004 kWh. At a typical rate of $0.12 per kWh, it costs only $0.0005 to dry a pair of hands with the BLAST!

Can I install a hand dryer on an existing electrical circuit?

That depends. Each hand dryer should have its own dedicated breaker. An existing circuit can be used if there are no other devices on the line and if the breaker rating is sufficient for the dryer and does not exceed the capacity of the wire.

Hand dryers like the Comac ONE and the Comac BLAST, which draw only 12.6 amps at 115 volts, can be safely installed on a 115-volt 15-amp circuit. Hand dryers that are rated higher than 1600 watts, and therefore draw more than 14 amps at 115 volts, will require a 20-amp or higher circuit.

All hand dryers must be installed by qualified electricians in accordance with national and local standards.

How many hand dryers will I need to install?

In a washroom with average traffic, install one conventional dryer per two washbasins or one high-speed dryer per three or four washbasins. In a heavy traffic washroom, double the number of hand dryers.

What are the advantages of hand dryers vs. paper towels?

Hand dryers offer many advantages over paper towels including cost savings of 90% or more, huge environmental benefits, washroom hygiene, and labor reduction. For a more detailed description of the benefits of warm-air hand dryers, please click here.

Do hand dryers spread germs?

No. There have been unsubstantiated claims by the paper industry that warm-air hand dryers spread germs or have other adverse health effects. In an independent study, the Mayo Clinic concluded that these claims were untrue. We encourage you to decide for yourself. Please click here to download the complete unedited four-page summary of the Mayo Clinic study in PDF format.

Hand dryers promote hygiene because washrooms are generally cleaner and more sanitary where they are used.

How much maintenance do hand dryers require?

Except for surface cleaning along with all other washroom fixtures, hand dryers require almost no maintenance. Most manufacturers recommend only vacuuming excess dust from the dryer internal mechanism once or twice per year depending on the environment.

In a typical hand dryer there are fewer than a half-dozen components that will eventually wear out. The Mean Time Between Failures of a quality hand dryer is at least five years. The Comac BLAST is fully guaranteed for 10 years and the Comac ONE carries a 12-year warranty.

What is the difference between a conventional dryer and a high-speed dryer?

A conventional warm-air hand dryer emits a large volume of air, heated to approximately 130F by an electric element, to evaporate moisture from the hands in approximately 30 seconds. The best conventional dryers are compact, attractive, quiet, comfortable to use, and exceptionally long-lasting. The Comac ONE, for example, protrudes only four inches from the wall, produces less than 60 decibels, and is guaranteed for 12 years.

A high-speed dryer typically employs a powerful vacuum-type motor to accelerate a concentrated jet of air to a velocity of over 150 mph. In the process the air is heated by the motor so a relatively small element, or in some cases no heating element, is required. The high-velocity air blows water droplets from the hands and breaks up and vaporizes the residual moisture in as little as 10 seconds.

Although the motor in a high-speed hand dryer requires more power than that of a conventional dryer, the electrical consumption is offset by the smaller heating element. The Comac BLAST, for example, consumes only 1.45 kW – the same as the Comac ONE and less than many other conventional dryers. In addition, the 10-second vs. 30-second drying time results in overall power usage at least three times lower than traditional models.

High-speed dryers produce more noise than conventional dryers, partly because of the more powerful motors but mostly because of the sound that the high-velocity air makes as it passes over the user’s hands.

How is hand dryer performance (CFM or LFM) measured?

The standard measure of performance for conventional hand dryers is air volume, expressed in Cubic Feet per Minute (CFM). For a given temperature of exhaust air, the greater the volume of air, the faster and more satisfying the hand drying experience. A high-quality warm-air dryer like the Comac ONE produces 150 CFM of air, heated to 138F, and dries hands in approximately 30 seconds.

In contrast, the performance of high-speed hand dryers is measured in air speed and expressed in Linear Feet per Minute (LFM). The velocity of the air is more important than the air volume for the efficient operation of this type of dryer. The Comac BLAST, for example, exhausts 138F air from the nozzle at a velocity of 16,000 LFM and dries hands in approximately 10 seconds. Some manufacturers list the air speed in meters per second or miles per hour instead of LFM. 16,000 LFM is approximately the same as 81 m/sec or 182 mph.

How is hand dryer noise (decibels) measured?

Sound energy, what we hear as loudness, is measured in decibels (dB). There are many methods to gauge sound energy but, like most mechanical equipment, hand dryers are usually tested on a scale measuring human-audible noise and in a non-reflective environment. The dryer is operated without any hands in place and readings are taken, depending on the manufacturer, at a distance of one meter from the front of the dryer or at the normal position of the operator’s ear.

According to this standard method, the Comac ONE produces approximately 60 dB and the Comac BLAST approximately 83 dB at the operator’s ear level. In real-world situations, decibel readings will be higher because of ambient noise (a quiet room normally registers 40 dB or more), reflective surfaces in the washroom, and in the case of the high-speed dryer especially, the sound of the air rushing over the hands.

What types of motors do hand dryers use?

Conventional warm-air dryers may employ either Universal (brush-type) motors or brushless AC motors. Universal motors are capable of producing high RPM, so they are able to generate excellent air volume when paired with relatively small ‘squirrel cage’ type fans. Brushless AC motors have the advantage of no brushes to wear out, but since they spin at lower speeds than Universal motors they must be paired with larger-diameter fans.

The Comac ONE employs a type of brushless motor known as an external rotor impellor, where a compact and highly efficient motor is located at the center of a large diameter fan wheel. The motor and wheel are turned 90-degrees compared to older designs so that they lie flat against the wall and result in a dryer that protrudes only four inches. The lifespan of this type of motor is almost unlimited and the large-diameter, low-rpm blower is extremely quiet and vibration-free.

A true high-speed dryer like the Comac BLAST, as opposed to conventional dryer with an oversized motor, employs a vacuum-type blower. It consists of an extremely high-speed (20,000 RPM) brush-type motor in a housing with a vacuum impellor. This arrangement draws in and compresses the air, raising its temperature and allowing it to be forced out of the dryer at high velocity though a relatively small nozzle.

What is the difference between painted and porcelain finishes on hand dryer covers?

Painted finishes, including epoxy, polyester, or other powder coat materials, are susceptible to scratches, graffiti, yellowing and staining. They may be attacked by solvents, harsh cleaners or abrasives and will become less glossy and less soil resistant over time.

Porcelain enamel, whether on steel or cast iron, is actually a thin layer of ceramic. It is comparatively scratch and stain resistant, will not change color, will resist acids and solvents and will maintain its original appearance indefinitely.

What are the ADA protrusion requirements for hand dryers?

According to the ADA (Americans with Disabilities Act), “Objects projecting from walls…between 27 in and 80 in above the finished floor shall protrude no more than 4 inches into walks, halls, corridors, passageways, or aisles”.

In practical terms, any hand dryer may be installed over a counter or in an area that is not a passageway. In areas where there is foot traffic, however, hand dryers may not protrude more than 4 inches.

The Comac ONE, at 4 inches in depth, complies with the ADA in any location. Most other hand dryers must be installed either outside of passageways or recessed into the wall.

How do I choose a hand dryer model?

First, determine whether a conventional or high-speed dryer is preferable. High-speed dryers like the Comac BLAST are faster and consume less energy. Conventional dryers like the Comac ONE are significantly quieter. In addition, the Comac ONE protrudes only 4 inches from the wall and offers unparalleled durability.

Whenever possible, choose a hand dryer with a porcelain enamel rather than a painted finish. In locations where vandalism is not a major concern, a stainless steel or chrome dryer will also maintain its appearance over time. Of course, the aesthetics of the dryer may also be an important factor.

When energy conservation or installation on an existing 115-volt 15-amp circuit is desirable, select a hand dryer that consumes less than 1600 watts. Both the Comac ONE and the Comac BLAST consume only 1450 watts. In addition, both models feature universal voltage circuitry for the ultimate in installation flexibility – they instantly and automatically adjust to input voltages of 115, 208 or 230V.

Finally, consider the total cost of ownership. It costs money to install or replace a hand dryer; so do not sacrifice quality for the lowest price. Choose a dryer that will last many years without loss of performance or deterioration in appearance.

The Comac BLAST carries a 10-year warranty and features a ¼-inch thick cast iron porcelain enameled cover. The Comac ONE offers the choice of a porcelain-enameled steel or a stainless steel cover and features a unique modular mechanism that can be unplugged and replaced without special tools or the need for an electrician. The ONE is warranted for 10 years.