brooke we're on the top story of a seven-floor building in san francisco. the radiation detection unit here, this silver box, you can see what it looks like when it's open. some computer equipment. there's a bit of a filtration system that analyzes the air and is able to provide real-time data to the epa. joining us to talk about how this system works is eric stevenson with the bay area air quality management district. he manages this system for the epa. is this pretty simple equipment? explain, give us an overview of how it work. >> the operation is industry straightforward. a volume of air is passed across a filter. the material that's deposited is analyzed for radioactive material. beta particles, gamma-rays, that information is sent directly back to the national air and radiation environmental laboratory in montgomery, alabama, where it's monitored on a regular base.