Continuity mistake: After returning from the Daedalus, McKay talks to Nola about how he had been a god to them the past years. In the shots filmed from his front, the standard radio headset is visible in his ear. In the shots from behind, it is gone.
Continuity mistake: In several scenes (mostly on the planet) we see characters reacting to tactical information from the oracle as if it's displayed in real time. However, the units in the display are moving far more quickly than they could in real-time.
Answer: Those are actually suits that protect from hazardous chemicals. They are cheaper for the prop department and look nearly the same as biohazard suits. A real biohazard suit would indeed have a helmet that seals to the neck.
Grumpy Scot