UFFI or UFI is a type of insulation composed of a urea formaldehyde resin. When mixed with a foaming agent and compressed air, it is easily injected into exterior wall cavities, which is a much more cost effective method of adding exterior wall insulation to existing homes than more conventional insulation.

In the insulating process, a slight excess of formaldehyde was often added to ensure complete "curing" with the urea to produce the urea-formaldehyde foam. That excess was given off during the curing, almost entirely within a day or two of injection. Properly installed, UFFI might not have resulted in any problem. Unfortunately, however, UFFI was sometimes improperly installed or used in locations where it should not have been. Enough complaints were received, particularly from people living in small, well-sealed homes, that Canadian authorities became concerned about possible health implications. The further use of UFFI was banned in 1980.

To collect a UFFI sample, cut or pull off a small piece of insulation (size o a penny) and place it in clean Ziploc bag. Label the bag to identify the sample location, like “123 Odessa Rd. , NE wall”.