As a precaution, part of the hospital was closed and crews evaluated and transported about 20 patients.
Kingston Fire said it has sent two ambulances to a report of some sort of "chemical release" in the emergency room at Exeter Hospital.
Multiple ambulances responded to the hospital just before noon on Friday.
Aerial footage captured this morning shows a row of gurneys outside the hospital's emergency room, where patients were being traiged.
State and local officials are still working to determine a cause.
Epping Fire said it was dispatched for a "carbon monoxide problem".
A hospital spokeswoman told the Union Leader that staff and patients began complaining of dizziness and nausea around 11:15 a.m. At this time, the cause is unknown.
Vasapolli said all affected staff members have either been released or transferred to other hospitals. About 40 patients and some staff experienced flu-like symptoms after the odor was reported, the source of which remains a mystery, according to the Boston Globe.