It turned out that the worker had noticed a bit of dirt on the tube and was trying to be helpful by changing it for a clean one. What he didn't realize is that the ultraviolet rays wouldn't have been affected by a bit of dirt.
原來工人早先看到特殊玻璃管有些臟，便好心把它換了，根本不知道紫外線是不會因少許汙點而受影響的。