The present invention provides a method of monitoring the position of a vehicle, vessel, rail car, barge, tanker truck that is loaded with bulk or hazardous material. A G.P.S unit is set to send a signal to a radio transmitter if the unit moves beyond a maximum permissible distance (for example, 50 feet or more). An oxygen sensor can be used to send a signal to a radio transmitter if oxygen levels fall below a selected minimum concentration. The radio transmitter can send the message to a tugboat crew, police department, fire department, company headquarters, civil defense office or other personnel if either of the unit has moved beyond the selected maximum travel distance or if oxygen levels fall below a minimum concentration. In addition to the radio transmission of oxygen concentration data and/or G.P.S position data, visible or audible alarms can be used such as strobe light, horn or the like. Also disclosed is a system for concealment of chemical and/or biological sensors in a building for urban or industrial environments.