Henry tells Jack he smells. Jack says he was in the methane abatement lab. Methane is an odorless colorless gas.
16:16 - As the smart dust doubles meet each other, you can tell the lag between the stunt doubles and the characters.
16:14 While you can only see Carter's hand in the mirror collision of the jeep, you should be able to see two impressions in the jeep even in camera view. They hid the stunt double carefully only showing the hand.
At the smart dust test site the colored cables on the ground are obvious CGI. Vehicles and people pass right through the cables.