The author conducted an experiment to evaluate the isolation of a new-built building to particulate matters (PM(s)) when the windows were shut and the entrance door was closed. The experiment was undergoing during a 5-day vacation when no resident was at home. The PM2.5 and PM10 were measured by Plantower PMS7003 placed in enclosed boxes with pulling fans. The initial finding indicates ratios of PM(s) inside building to the outside environment (I/O) are 83-86%. Ratios of PM2.5/PM10 of the inside and the outside are in the range of 84-86% making only a small significant difference of particles profiles. The I/O ratios of PM(s) shows a distinct diurnal pattern in which the ratios are higher during the day and lower during the night. Those findings are disappointed to the author who hypothesized that the internal building environment should provide better isolation than a reduction of 14-17% of PM(s) as above.