If you occasionally have nosebleeds then go to a doctor and tell him
A) How often you have them
B) What meds you are on as some eg asprin make things worse
C) list what other symptoms you have, even if you think they are u related or insignificant
D) what chemicals you are exposed to at work. For instance, ammonia, sulphuric acid and gasoline will give you nose bleeds.
You may be referred to to an ENT ie otolaryngologist who will examine the nasal region with a scope ( under local anaesthesia, this will not hurt. I have had this performed on me many times) or he'll recommend a scan.
This will get to the bottom of the matter.
If it is found that the chemicals are causing you the bleeds then the solution is straight forward.
Good luck.