Problem/Objective: A significant fraction of the air and secondhand smoke in apartment buildings is often “shared” between units.

Methods: Air sealing and ventilation improvements were applied to six different Minnesota apartment buildings. Extensive air leakage, tracer gas, particulate, and nicotine measurements were conducted before and after the improvements.

Results: Tracer gas tests determined that for the units on the upper floors the fraction of air from other units within the building was as high as 65% with a median of 16%. The median fraction for lower level units was only 2%. Pressure tests showed that 16% to 59% of the unit air leakage is to other parts of the building. Many of the leakage paths are small and diffuse, like the leaks around kitchen or bathroom plumbing pipes. Air sealing reduced inter-unit leakage by 15% to 54% for three of the buildings, but had little effect on leakage at the other buildings. The installation of continuous, exhaust ventilation increased the average ventilation rate by 60%. Overall, the treatments resulted in a 68% reduction in SHS concentration in adjacent units. A total of 80% of the tenants reported that their SHS transfer problem was less frequent and less severe.

Conclusions: Focus on sealing large openings and installing balanced, continuous ventilation. Air sealing and ventilation treatments can have a noticeable effect on SHS transfer, but these methods can not eliminate the transfer.