You might see lab-coated technicians and scientific equipment on the subways outside of Charlestown through Aug. 5, as government officials test our understanding of chemical and biological attacks.

Officials say not to be alarmed. They will be releasing odorless gasses and particles at 20 stations in an effort to map how actual pathogens might move through the T and, perhaps, onto the streets of Boston.

Several Orange Line stations are involved in the tests. That's the main commuting line for JP residents.

These tests are different from previously-announced ones in which a dead bacteria will be released at a handful of Red Line stations to check biological attack sensors. The bacteria-based tests, to be done when the T isn't running, are scheduled for later this summer.

The gas and particle tests will take place mostly during off-peak hours.

Here is a list of stations where the testing is being done:

• Downtown Crossing (orange)
• State (orange)
• Haymarket (orange)
• North Station
• Downtown Crossing (red)
• Davis
• Harvard
• Kendall
• Park (red)
• South Station
• Andrew
• New England Med Cntr
• Haymarket (green)
• Government Center (green)
• Park (green)
• Boylston
• Copley
• Government Center (blue)
• State (blue)
• Aquarium

For more on the tests being done through Aug. 5, please visit these articles at BostonInno and the Boston Globe.