Your standard UV rays come in two wave lengths....

UV-A
UV-B

Because of the thin glass most bulbs come in, most all A & B rays are distributed to the plant leaves.

Most often, it is not the light or the rays that fry the plants...rather it is the radiant heat that comes from the reflectors.

The surface of a plant is far more sensitive to radiant heat than the human hand is. That hand test is good for testing burn temps but prolonged exposure to radiant heat will fry a plant in a matter of hours.

The UV rays damage the plants chemistry....not the foilage.

The MJ plant produces more resin to protect the flowers from the UV-B rays thus negating the damaging effects.

Neither UV-A nor UV-B from an MH bulb will kill a plant.

Besides.....your HPS bulbs emit almost ZERO UV-A or UV-B rays.

So we know it isnt the bulb itself then.

Again, its almost always the case of using a relector that causes the radiant heat burn / crisp / death.

And, a 1000W bulb needs to be placed a nice distance from the tops. At least 18" or more.
HARDDON Reviewed by HARDDON on . what ventilation system should i be looking for? O'k guys I have a few question concerning my grow room,I was wondering what I could use to dump the heat in the room and at the same time draw fresh air back into the grow room......here is my set up... The room is 9ft long 5ft wide and 8ft high my grow table that I have my plants on is about 5ftx4ft under a 1000w hps I am into my 3rd week of flowering and boy is the room getting hot! alot hotter then I anticipated!,I keep opening up the door to the grow room and at most times I leave Rating: 5