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Table 1 Median concentration of polychlorinated biphenyls in indoor air before and after implementation of three mitigation measures, normalizing for temperature and ventilation rates.

From: Mitigation of building-related polychlorinated biphenyls in indoor air of a school

Period Number of Rooms Median (ng/m3)1 H0: medians are equal (p-value)6
Ventilation 2
August 25-27, 2010 9 432 < 0.01
September 6, 2010 10 149  
Encapsulation: Directly Accessible Caulk 3
September 6, 2010 10 282 0.08
September 19, 2010 7 220  
Encapsulation: Behind Built-in Equipment and Furniture 4
September 19, 2010 7 220 0.02
September 29, 2010 5 133  
False Wall 5
September 29, 2010 5 133 < 0.01
Nov. 4 - Dec. 2, 2010 19 76  
  1. 1 Median of temperature-normalized and ventilation-normalized concentrations
  2. 2 Ventilation rates were improved by replacing filters and repairing fans in the unit ventilators. Median of temperature-normalized, but not ventilation-normalized concentrations.
  3. 3 PCB-containing caulk along the interior face of transite panels open to classrooms was covered with adhesive-backed polyethylene tape and sealed with silicone caulk.
  4. 4 PCB-containing caulk located behind unit ventilators and convective heaters was covered with adhesive-backed polyethylene tape and sealed with silicone caulk.
  5. 5 False walls constructed over encapsulated PCB caulk and adjoining transite panels and framing.
  6. 6 Wilcoxon rank sum test of the hypothesis that the median pre-intervention and post- intervention concentrations are equal.