WASHINGTON -- Amtrak wants to improve its ability to detect a bioterror attack at Union Station.

The railroad plans to install a new sensor system that would detect a chemical or poisonous gas attack at the train station.

The sensors are housed in a metal box and continually test the air for toxins and gases. The system was developed after the sarin gas attack in a Tokyo subway in 1995

Amtrak also plans to install the so-called sniffers at New York's Penn Station and at stations in Chicago within the next eight months.