With reference to FIGS. 9 and 10, a device such as a blower or a fan 130 creates a vacuum in housing 112 for drawing the gas through inlet 114 (FIG. 9), past one of aplurality of collectors 140 (FIG. 9), through fan 130, through a muffler 155 (FIG. 10), past a Geiger counter or radioactivity sensor 157 (FIG. 10), and out the bottom of the housing via a chamber 115 disposed along the side of housin