a vent cover for installing on a shipping container . the vent cover includes a housing adapted for covering a vent hole of the shipping container . a direct current power source is encased or enclosed in the housing . the dc power source includes a battery . the vent cover may also include a circuit board attached to the dc power source . an antenna may be located on a surface of the housing and attached to the circuit board . the circuit board may include a satellite antenna interface for a satellite antenna and a global positioning system module attached to the satellite antenna interface . the vent cover may include an environmental sensor for sensing a parameter of the shipping container . the environmental sensor may be adapted to protrude through a hole in a wall of the shipping container when the vent cover is mounted on the shipping container . the electromagnetic sensor may be configured to transmit an electromagnetic signal and sense an electromagnetic response signal responsive to the transmitted wave and sensitive to variations within the container .