The Hab has three airlocks. Airlock 1 is the one Mark used the most as it was closest to the Rover, the solar panels, etc even though he was meant to alternate between 1, 2 and 3.
Because of this the strain on the airlock was too much, AL102 stretched and it ended up malfunctioning and launching Mark several metres from The Hab, breaking his helmet and killing his potato plants in the process.
Mark looking at his ruined potatoes after the breach.
After this unfortunate event it was replaced by some Hab canvas and some duct tape.
A quote straight from the book praising Duct tape.
The Hab after the breach with the hole covered in Hab canvas and duct tape.
