A roughly square mile swath of midtown will become the testing ground Monday for how city streets and the subways beneath them would fare in a hazardous chemical attack.

But instead of harmful fumes, colorless, odorless and benign "tracer" gases will be released by a team of 150 scientists and volunteers participating in the federally funded project, organizers said.

The tests are part of a massive project funded by the Department of Homeland Security, which will determine how chemicals or fumes spread in the streets, subways and inside buildings.

Monday's tests, the first of six separate experiments planned during the next three weeks, were to take place over the weekend but were rescheduled because of weather. In March, a smaller experiment focused on the Madison Square Garden area.

Data about how the gases spread will be collected by electronic monitors on rooftops, subway stations, lampposts and unmarked vehicles. Volunteers walking the city in an area ranging from 37th to 59th streets and 10th to Third avenues, will also carry monitors in their pockets.

Mayor Michael Bloomberg yesterday said the public should be reassured by these tests.

"It gives us a chance to have an exercise so that everybody studies how they would respond ... This is a normal thing," he said.

Courtesy of Newsday

Luis Perez-Newsday