Oh, dear, NamLan. What have you started here?
Workplace may be a common word in Australia, where Cyclone comes from, but I don't think I have ever, until now, either spoken or written this word. When I read your two sentences, I wondered which part of the human body is the workplace.
I think "at work" was a much, much better way of putting it, and it fits into both of your sentences perfectly.