Working with women co-workers

I work with Muslim females in a Muslim company. Some females wear niqaab. Is it correct for females my age and/or younger to make salaam to me and ask me how I am? Will I be sinning if I do not reply to their salaam and do not initiate salaam to them. Will I be correct Islamically, to just say what I have to, to them (like issuing instructions relating to work) and not greet them or engage in chit chat. I generally look down and talk to them, but even the ladies with niqaab tend to stare me in the eyes, and when they see I am trying to not make eye contact, they stare even harder waiting for a reaction from me. When a woman wears niqaab and generally any muslim woman is she allowed to look at men in their eyes/faces?