I really like st. Vitus church but the only thing is not good for my health is the incense burning at mass. So which mas is incense burning?.

The 9AM and 11AM are "High Masses", so with full solemnity. I'm afraid you would have to go to the 7:30AM or the 5PM Low Masses on Sundays for there to be no incense. During the week most Masses are Low, save on Holy Days where there's normally at least one High. Hope this helps! Alternatively, there's usually seating in the choir room during the 9AM. You could probably escape the incense back there.

You could step into the vestibule if you needed to, too. I get a little sensitive to incense, so I either cover my mouth and nose or I step back a bit so it's not so overwhelming.

Incense is burned at Solemn High Mass and at Funeral Mass. Usually at Low Mass is when incense are not burned if I am not mistaken. You may still be able to attend Mass where incense are used as long as you sit near the front door.