For those who want to participate, an add-on sensor to your PDA and/or Cell Phone that can sense the presents of volitile material can be designed. Once installed and activated, this information along with GPS coordinates could be feed into a Homeland security data warehouse for analysis. If the data indicates a gas station or fueling a lawn mower at home, then the data could be scrubbed. However if the sensor indicates a response for a mass transit or other public area, a flag can be raised to have this investigated. Other variations on this theme can be employed such as stationary locations in public areas for sensing, etc.