This information was collected from a press release at CityofChicago.org:
Departments of Buildings, Zoning Task Force Targets Illegal Conversions
Inspectors Cite Owners of Illegal Apartment Units
An illegal conversion occurs when a building owner constructs additional living space that is not allowed by building or zoning code.
On February 23-25, 2005 a task force of City building and zoning inspectors visited 57 locations in the Archer Heights, Brighton Park and West Lawn neighborhoods, and wrote scores of citations for code violations.
"When landlords illegally convert their single-family homes into multiple dwelling units, they often cause unsafe situations," said Department of Buildings Commissioner Stan Kaderbek. "Our joint task force took immediate action against a serious problem."
The most commonly cited building code violations included: no emergency exits; no ventilation equipment for kitchens or bathrooms in basement and attic apartments; inadequate heating systems for attic apartments; and inadequate light and ventilation for basement apartments.
FYI: Carbon monoxide (CO) is a odorless, colorless gas produced by burning fossel fuels (Fossil fuels shall include natural gas, coal, kerosene, oil, propane and wood etc.) Exposure to lower levels of CO over several hours can be just as dangerous as exposure to higher levels for a few minutes.
Those most at risk are:
3. People with lung or heart disease.
4. Pregnant women.
Signs and symptoms of CO poisoning include:
5. Nausea, Vomiting.
6. Dizziness, Confusion.
7. Trouble breathing.
In NYC, an adult family member may stay in a basement bedroom without penalty, but it is not recommended for a guest (e.g. tenant or anyone else), so I am assuming there is a personal liability / insurance issue in addition to the possible health hazzards. Regards, C.