Yesterday, the Department of Buildings revealed that it conducted an undercover investigation of illegal apartment conversions—the agency's investigators went to Craigslist's rental sections, posed as potential tenants, and found "illegal living conditions in 54 of the 62 rental apartments inspected, including fire safety hazards such as inadequate means of egress, untested gas lines and single-room occupancies with locks on individual rooms." The agency showed a tape of one of those residences and issued ten tips for renters.

Thirty-three of the properties were issued vacate orders because they were an "immediate threat to public safety" and the other properties were fined. Mayor Bloomberg said, "Illegal conversions can have deadly consequences, and too often we have seen that tragic result. Illegal conversions pose a serious risk to tenants, neighbors and first responders. Property owners who create these illegal living spaces are compromising public safety." (Case in point: The 2005 Black Sunday fire. More recently, a fire injured tenants of a Bronx illegal conversion.) And DOB Commissioner Robert LiMandri said, "It is wrong for property owners to rent these illegal living spaces for thousands of dollars each year while putting tenants in harm's way."

Ten tips about "illegal conversions" for renters:

1) Know the market. Be wary of units that advertise significantly lower price points for comparable apartments in the area.

2) Beware of the words “basement” or “attic.” Advertisements that use these words are often for apartments that typically lack adequate exits.

3) Avoid apartments that have rooms without windows or very small windows. These are often found in illegal cellar or basement apartments. Landlords will sometimes describe the ones with very small windows as “sunny” to entice renters.

4) Beware of the word “flex.” “Flex” implies that the apartment can be converted into a multi-bedroom unit using pressurized walls. The installation and/or construction of a wall without the proper permits from the Department are illegal.

5) “Utilities included” is a red flag. A landlord may not want utilities under another name connected to the property because those residents would violate the legal occupancy of the building.

6) Avoid apartments with odd layouts. They are often described as “unique” or “interesting” and are oddly situated (i.e. a shower installed in the kitchen).

7) Be cautious when a landlord refuses to disclose the exact address. Landlords advertising illegal apartments may ask to meet a potential renter before exposing the address to possible regulation or penalty.

8) Beware of apartments where you can’t have mail delivered. Landlords advertising illegal apartments will often request that tenants obtain a separate P.O. Box.

9) Beware of no-lease apartments. Be suspicious of a landlord who declines to draw up a lease, requests a month-to-month agreement or requires cash payments.

10) Check for adequate means of egress and look out for locked doors in the unit. A tenant should be able to access all available exits either directly from the unit or a public hallway.