250 hps light. how far from plants.

iv,e just bought 250 hps light, and I'm wandering how far from plants should they be, and are they safe to leave on 24 hours a day, until my flowering stage, .

thanks for any help i can get.

seven to twelve inches

generally, if you can hold your hand under the lamp for several minutes at the same distance as the top of the plant and not feel discomfort, then your plant won't feel discomfort either.

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24 hrs a day is okay...although I prefer to give them at least four hours of darkness during veg stage.