What causes flashes of light in your eyes and once in a while dizziness. This has been occurring to my husband for a week or more, should he be concerned (he is working out of town)

Vitreous. This the classic symptoms of a vitreous detachment. The flashing lights are the tugging on the retina. He should have his eyes looked at soon. There is a small chance of this causing a retinal detachment later.
Flashes . Flashes of light can indicate a serious problem. If associated with floaters, flahes could indicate a retinal tear. Your husband should have an eye examination. The link below will explain this further.