Continuity mistake: When they finally get through the gate by blowing the rear hatch (which serves as the exit ramp when open), they arrive on the other end with the ramp closed.
Continuity mistake: Right at the beginning, the crew of the jumper only dials five symbols into the DHD before hitting the engage button.
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