How long has the man suffered from the symptoms he described?

M: Good morning, Doctor.
F:  Good morning, Mr. Smith. What can I do for you?
M: I feel there’s something wrong with me, but I’m not sure.
F:  Could you explain to me more?
M: I usually get a runny nose, watery eyes, scratchy throat and other symptoms on Monday. It will last for the following five days. And since I am terrible busy with my work, I won’ t have time to see the doctor. But when I do have time to see the doctor on weekends, the symptoms will disappear all of a sudden!
F:  And you will get same symptoms again next Monday?
M: Exactly.
F:  How long have you been like this?
M: About one month.
F:  Did anything special happen during the past four weeks?
M: Nothing special. Oh, wait! My company has moved from the old address to the present Mount Plaza.
M: That is it. When a new building is just finished, the chemical vapors being given off by glue, paint and other construction materials and moisture can’ t escape, the building, just like people, can’ t breathe properly. So it gets sick.
F:  Well, I got the reason. Thank you, Doctor.
M: Wish you good luck.