Which humidity condition is associated with increased static marks on film?

• A. Above 60%
• B. Between 40% and 60%
• C. Below 40%
• D. No relation to humidity at all

Answer: (C)

Low humidity increases static electricity on radiographic film. In dry air, there isn’t enough moisture to help carry away electrical charges, so friction during handling, loading into cassettes, or moving the film can build up charge on the film surface. When that charge discharges, it creates static marks on the film, often appearing as fine, branching patterns. Therefore, humidity below about 40% is the condition most associated with more static marks. Higher humidity helps dissipate charges, reducing static, which is why conditions with humidity above roughly 60% show fewer static marks.