Plans call for the release of a colorless, odorless gas over a three day period in May to trace its dispersion around and through the landmark military headquarters on the banks of the Potomac River in Virginia.

"The tracer gas will simulate how chemical or biological agents would flow around and into the Pentagon," the Pentagon said in a statement.

Called "Pentagon Shield," the exercise is being conducted by the Defense Advanced Research Projects Agency and the Pentagon Force Protection Agency from April 19 through May 15.

Sensors are being placed atop light poles, rooftops and a tower erected in Arlington National Cemetery, which abuts the Pentagon grounds, to collect information on wind speeds, wind direction, temperature and other data, the Pentagon said.

A blimp stationed in a Pentagon parking lot also will be used to gather information on wind speeds at various altitudes.

Two long-range lasers will be used to measure winds around the Pentagon grounds from a nearby Navy facility.

"Knowledge gained about the airflow around the Pentagon, and the associated transport of gases and their infiltration into the building, will allow the development of improved systems for protecting other Department of Defense facilities," the Pentagon said.

The Pentagon emphasized that the tracer gas being used, sulfur hexaflouride, was safe and that the testing protocols have been used in other locations.

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