Figure 1.

Setup of the gas chamber for Experiment 1. The two treatment gases (CO₂ and N₂O) went from the tanks to the mass flow controllers (1), into the chamber box (2), and then out of the chamber with help from a ventilator (3) and a gate valve that allowed the system to be flushed (4). A vacuum pressure pump (5) kept the system under a slight negative pressure that was measured by a manometer (6). Acrylic glass (7) allowed visualization of the piglets. To check for palpebral reflexes there was a glove assembly (8) for reaching into the chamber.