According to Chicago Building Code
18-28-504.1 Installation.
Clothes dryers shall be exhausted in accordance with the
manufacturer’s instructions. Dryer exhaust systems shall be
independent of all other systems and shall convey the moisture and any
products of combustion to the outside of the building.
Exception: Where the make and model of an electric dryer is known
and the manufacturer’s installation instructions do not require
exhaust, see Article 4, Ventilation for room exhaust requirements.
Venting a dryer inside is a potential fire and mold hazard, and can negatively affect indoor air quality causing sickness (and/or death, maybe).
You should bring this up with the condo association, the building owner, and potentially the building inspector. A possible down side to this action is, the condo association could ban the installation of dryers altogether. So you'll want to try and suggest some alternatives.
I'm going to guess, the condo association is worried about the appearance of vents sicking out all over the building. A potential appeasement would be to select a nice looking vent (voted on by the condo association), and force anybody who installs a dryer to use the same vent.
They may also want all vents to be installed in similar locations, so the vents are uniformly placed on the building. A good way to insure this would be to install all the vents at once, including installing vents for units without dryers (in which case they should be sealed until in use).
Your duct is probably too long, and not constructed properly. Installing a proper exhaust system may increase the dryers performance, though this is not guaranteed.
Vent length and installation requirements will vary slightly from manufacturer to manufacturer, but International Residential Code (IRC) gives us a conservative starting point.
International Residential Code 2009
Chapter 15 - Exhaust Systems
Section M1502 Clothes Dryer Exhaust
M1502.1 General. Clothes dryers shall be exhausted in accordance with the manufacturer's instructions.
M1502.4 Dryer exhaust ducts. Dryer exhaust ducts shall conform to the requirements of Sections M1502.4.1 through M1502.4.6.
M1502.4.1 Material and size. Exhaust ducts shall have a smooth interior finish and shall be constructed of metal a minimum 0.016-inch
(0.4 mm) thick. The exhaust duct size shall be 4 inches (102 mm)
nominal in diameter.
M1502.4.3 Transition duct. Transition ducts used to connect the dryer to the exhaust duct system shall be a single length that is
listed and labeled in accordance with UL 2158A. Transition ducts shall
be a maximum of 8 feet (2438 mm) in length. Transition ducts shall not
be concealed within construction.
M1502.4.4 Duct length. The maximum allowable exhaust duct length shall be determined by one of the methods specified in Section
M1502.4.4.1 or M1502.4.4.2.
M1502.4.4.1 Specified length. The maximum length of the exhaust duct shall be 25 feet (7620 mm) from the connection to the transition
duct from the dryer to the outlet terminal. Where fittings are used,
the maximum length of the exhaust duct shall be reduced in accordance
with Table M1502.4.4.1.
M1502.4.4.2 Manufacturer's instructions. The size and maximum length of the exhaust duct shall be determined by the dryer
manufacturer's installation instructions. The code official shall be
provided with a copy of the installation instructions for the make and
model of the dryer at the concealment inspection. In the absence of
fitting equivalent length calculations from the clothes dryer
manufacturer, Table M1502.4.4.1 shall be used.
Basically what all this means, is that in general the overall length of the duct can be 33'. 25' of the duct system; measured from the exhaust hood to the dryer connection, must be 4" rigid metal duct. You can then have an 8' section of "transition duct", which can be flexible duct, but must be UL listed and labeled for the use. For each elbow, subtract the value from Table M1502.4.4.1 from the overall 25' length.
When you use flexible "transition duct", make sure the duct is fully extended and trimmed to fit. Don't leave the duct compressed and coiled.
Manufacturers Installation Instructions
If you look at the Maytag installation instructions (PDF), they tell you what type of exhaust hoods you can choose from.
The instructions then provide a table to determine the maximum duct length, based on the hood used and the number of bends.
Gas dryers need gas to dry, so make sure the gas is on before you spend too much more time or money on repairs. It might also be useful to make sure it's not user error, by making sure the tenants know how to use the dryer properly. Don't forget to make sure the tenants aren't overloading the dryer.
Best Answer
This is one possibility from my history. Some vent systems don’t handle the extra moisture.
yes at the start of a dry cycle the humidity is off the charts, however as the cloths dry and the same volume of air continues to be pushed out the moisture in the vent is reduced.
with the steam setup some moisture is pumped into the vent but the cycle is finished quickly not drying the vent causing mold issues.
I did maintenance for a slum lord friend and he had this problem with his fancy steam dryer some years back and thought it was electrical, after that steam dryers were not allowed, it was in his lease agreement sounds like the same issue to me.