Yes, thats what I do. I use my CFL's for vegging because I find that my plants fill out more and get a bit bushier and not so tall. Recently, I did something I'm against and thats vegged 4 plants with my HPS due to lack of space in my veg cab. Thus far, I'm seeing that they are more stretched than usual (I grow this strain regularly so I know what to look for) and they sidegrowth seems to have weaker stems (thinner)

In theory, you should be ok just closing the closet door at night when the lights are off. A ventilation system would be ideal, however if thats not possible just make sure you remember to shut the door on time or else your plants will get an improper light schedule and you could find yourself ending up with hermies.