I created this web page because these are the quietest
small room humidifiers avaliable, but I found
conflicting reviews of the Air-O-Swiss 7135, no reviews
Venta VS 207 online, and that both models consistently
underreport ambient humidity. The Venta VS 207 is apparently
new enough that nobody has reviewed it, and the Air-O-Swiss
seems to give different results to different users, perhaps
due to manufacturing inconsistencies. Also note that the
frequently cited Allergy Buyer's
Club is a vendor of Air-O-Swiss brand only, which may be
why they omit Venta from their reviews.
Air-O-Swiss AOS 7135 vs. Venta-Sonic VS 207
by Carson Wilson
Last update: 02-Dec-2009 03:04 PM
Venta-Sonic provides an online manual for the VS 207 in
PDF format here.
I have been unable to find an online manual for the
Air-O-Swiss 7135, so I am furnishing
one here. However, I did find an online
site for the 7135 by its manufacturer, Plaston AG.
At a Glance Comparison (advantages in green)
Venta VS 207
Humidity level control range
Humidity level control increment
Requires separate $30 silver stick yearly
Silver built into filter
Replacement cartridge cost
Cartridge refill pack
$19.99 for three resin refill
Cartridge pre-soak time
Cartridge replacement interval
2 to 3 months
2 to 3 months
Warm/Cool, Output Level, Target Humidity, Timer,
Warm/Cool, Output Level, Target Humidity
All but output level
Country of Manufacture
15.2 x 8.8 x 13.8 in
13 x 10 x 13 in
Cable length, color
72 in, black
72 in, white
Serial number of sample
This is an area of interest as smaller humidifiers are
often used in sleeping areas. Depending on background noise
levels, even a very quiet motor sound may disturb sleep. Both
the AOS and the Venta employ an electric fan to distribute
humidified air and therefore do generate some fan
noise. Claims that they are completely silent are
exaggerated, although even soft background noise such as
urban street sounds or a running furnace will render them
inaudible. However, I can hear the AOS from across my quiet
suburban bedroom, and in fact both units make a very soft 60
cycle hum even when powered off (but still plugged in). This
sound is about as loud as the motor in an electric clock.
Both models have well damped motor noise, but the Venta is
significantly quieter than the AOS.
Here are sound recordings of both models. Both units were
running at their highest output settings with tanks 1/2 full.
The sound was sampled using identical recording settings from
floor level, about 3 inches from the front center of each
unit. I've included identical background music (John
Coltrane's Summertime) to give you a consistent frame
Contrary to some reports, both of the models in my sample
generate periodic gurgling sounds as air enters the water
chamber through the valve which admits water to the
humidifier base. The Air-O-Swiss seems to gurgle more
softly, but this may only seem so because of its generally
higher noise levels.
The Venta makes a disturbing solenoid click when turning
its oscillator on and off as the detected ambient humidity
climbs above and falls below the user setting. The humidity
gauge is sensitive enough that this can occur several times
per minute once the selected humidity level is reached,
even at the lowest output setting. This may also be the
case with the AOS but I just haven't noticed it due to the
AOS' higher overall noise level.
This is a key difference. The AOS 7135 can be programmed
for output level, target humidity, timer, warm/cool, and
sleep and auto modes. However, all of these settings
are lost whenever the unit is powered off with its on/off
switch. Whenever it is powered on, the AOS reverts to
its "auto" mode. On the other hand, the VS 207 retains all
settings EXCEPT for output level, which reverts to maximum
when the unit is powered off with its on/off switch.
Both models lose ALL program settings when unplugged (which
must be done prior to cleaning).
If you power on the Venta when empty, it will flash its
display until enough water has been added for operation, at
which point it will return to operation. If you've
unplugged it, it will run at its highest output level
continuously. Under these conditions, I recall that the AOS
simply powers off after a brief period (please email me if
Hygrometer Accuracy and Range
Another key difference: my sample of the
AOS 7135 consistently reported a significantly
lower relative humidity than either the VS 207
Taylor HumidiGuide operating in the same location (about
$10. I highly recommend a HumidiGuide as a more accurate and
reliable gauge than either of these humidifiers'). The photo
to the left was taken after both humidifiers had run for
several minutes. Notice the humidiguide's reading of about
55% versus the AOS 7135's reading of 25% and the VS 207's
reading of 43%. Additionally the AOS 7135's lowest desired
humidity setting at 40% is 10% higher than the VS 207's
Both models indicate humidity levels at least 10% lower
than my Taylor HumidiGuide. I suspect the Taylor is
more accurate than either humidifier as a) the readings of
all Taylor HumidiGuides in the rack I purchased it from
were identical, and b) 50% relative humidity as measured by
either humidifier feels quite damp, whereas at 50% (the
level recommended in both manuals) on the Taylor the room
feels properly humidified. I also observed this with the
AOS 7135 and Venta VS 207's on display at my dealer, so
it's not limited to my sample. I am surprised at this and
can only speculate that the low readings are designed to
compensate for slow circulation in large rooms, where a
high humidity reading near the unit would translate to a
normal reading across the room. In a small room both of the
units I sampled overhumidify when set to 50%. The AOS will
raise humidity to well above 50% when set to its lowest
setting of 40%, so my strategy with it is to set its timer
to avoid this occurring overnight. With the Venta I set the
desired humidity to 40%, resulting in actual humidity
levels of about 50%.
Further note: AllergyBuyersClub says "
We recommend that indoor humidity levels in winter should
be around 30 to 40%." This may be a significant concern
about the AOS 7135 as the lowest setting it provides is
well above 50% (when it is set to 40%).
Both models claim to have eliminated "white dust"
through the use of demineralization cartridges. However, I
find they both still produce some white dust (actually it is
light grey in color) even when the cartridges are new. This
is with my city water which is neither excessively hard nor
soft. Also, both models recommend changing the filter
cartridge when white dust appears, several times per season.
So there is no total guarantee against white dust, just that
the filter cartridge greatly reduces it (until it doesn't).
The only total guarantee against white dust is an evaporative
humidifier (the new Slant-Fin with mineral-absorption pads is
probably the best), but these are significantly louder than
ultrasonics due to boiling noise. Personally, I have not
found the dust a problem after several months of use.
Placement in Room
Both models come with instructions to place them on a
raised surface as failure to do so may may cause water to
accumulate on your floor or carpet. I make no promises, but
my experience so far is that they may be placed on a hard
surface at floor level in a standard bedroom at room
temperature so long as the warm mist setting is used with the
lowest output setting. A hard surface must be used in
order not to block the air inlets in the base.
Cleaning Indicator (AOS only)
The Air-O-Swiss 7135 includes a cleaning indicator lamp
which continues to flash red until the lamp is reset by
holding the on/off switch for several seconds. This
apparently is not a true indication that any cleaning is
needed but is rather activated by a timer that accumulates
wall clock time since the last time the lamp was reset. This
is my conclusion as the lamp comes on when the oscillator is
not dirty (or even running) and does not turn off until
reset, at which point it does not come back on again
regardless of whether the oscillator has been cleaned.
When to change the filter cartridge?
Both units recommend changing the cartridge every
several months or as needed, and apparently "as needed" is
when you notice white dust (the AOS Manual on page 12
indicates "Demineralization cartridge exhausted" and
recommends you "Replace cartridge or granules" to remedy the
problem of "white around the humidifier"). As noted in the
table above, the Venta requires purchase of a new filter
cartridge while the AOS allows cartridge refilling. This
saves some money but is made up for by the need to replace
the AOS' $30 silver stick annually: e.g., replacing or
refilling the cartridge every 10 weeks during a 5-month
- AOS: $30 + 2/3 * $19.99 = $43.33
- Venta: $14.99 * 2 = $29.98
My overall advice: if you think you might want a quiet
humidifier for your bedroom,
- Invest in a Taylor HumidiGuide and see if you really
need humidification. If the HumidiGuide consistently
reports near or above 50%, you don't.
- If silence is a huge issue with you, the Venta wins. If
not investigate AOS.
- Whatever your strategy, use the humidifier sparingly
and clean it thoroughly with every filling. Keeping the
humidity much above 50% increases microbe growth, and if
you run your humidifier constantly dust will build up and
probably shorten its life.