Alison Bernstein, Ph.D.:
Masks are not dangerous and are safe to wear. Any reports of masks’ limited air flow are false.
But I think by “safe” this question is asking if a mask at work will protect you from coronavirus. This very much depends on what you do for work.
For this answer, I’m talking about cloth masks since that is what most people have access to right now. You are protected by the masks of your co-workers, customers, and other people you interact with. If you wear a mask and they don’t, you are not protected from them. If everyone in your workplace wears a mask and adjustments can be made to maintain physical distancing and good hygiene practices are implemented, this reduces your risk as much as possible. Certain occupations and jobs are more conducive to implementing these practices.