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