You're right... no point in whiting out anymore.

I'm just used to it.
I too made the leap of logic that their technology would tell them if the air was sterile or not, especially later when they're scanning the head to find out of it's sterile. There was nothing on the wrist display shown to confirm (or deny) this though and of course it wasn't in the dialogue. He was ordered not to remove his helmet, which was enough for me to dismiss it, though the biologist character should know better about contaminating the alien planet with our microbes and he also removes his helmet without issue. There's a whole job at NASA dedicated to preventing that, hence the stink recently about that person not being notified before the rover was launched that one of the parts was not sterilized (the drill). It's POSSIBLE that the rover has transferred microbes from Earth to Mars.
Now, we CAN assume that Weyland Corp. has no policy on this and thus it's not made an issue in the film, but at least the biologist would know this is a bad thing like I said. This calls into question his validity as a scientist and also makes it more likely for him to make such poor errors of judgment in the film. Again, none of this is explicitly stated or hinted at though.