Exhaust fan?

I just set up a grow room. It is 5ft long and 3ft wide. I have a T5 4ft 8 bulb light. Supposedly 40,000 lumens. The guy at the shop told me it would effectively light an area six inches larger that the actuall light giving me my measurements. First of all I want to make sure that it is not too big of an area.
Secondly I am going to run a four inch in line fan for an exhaust. My question is if I am running a low heat light will I need to run the exhaust full time? If not then how much? Also should I just put a hole in to let fresh air in or should I pump it in with another fan? If I can just put a hole in is there some kind of leuver set up that will open when the exhust is sucking out but not let air out when the fan is off?
Thirdly with this light how tall should I let my plants get before I force them to flower?

This light will work in that amount of space but only for vegging. You need an exhaust. If you space is enclosed run it 24 hrs. If you do you only need a space for the fresh air to come in. Sorry to stoned to remember the other questions.

Y will the light only work for vegging? I have both a set of veg bulbs (blue) and a set of bloom bulbs (red).

Welcome to the forum. The guy at my hydro shop believes that fixture will do better than a 600 watt hid light. More even grow and you can put the light closer to the plants so they will get more lumens / sqft. The rule of thumb for deciding when to flower is when they are 1/2 to 1/3 as tall as you want them to get, because they can double or triple in height from the time you do. Soo...how tall is your growing space. VV

you are right (told you I was stoned earlier)

Overall height of the room is 7.5ft but the top 2.5ft is for babies so I guess the answer to your question is about 5ft. Making the answer to my question 2.5 to 3ft. I am growing in soil and it is my first grow. I plan on buying a hydro set up after this grow is over but for now I am stuck. The plants are about a foot tall now and are very strong. I am wondering if I should buy a tester and start regulating PH or just keep ignoring it like I am doing now?

All4Me said:

Overall height of the room is 7.5ft but the top 2.5ft is for babies so I guess the answer to your question is about 5ft. Making the answer to my question 2.5 to 3ft. I am growing in soil and it is my first grow. I plan on buying a hydro set up after this grow is over but for now I am stuck. The plants are about a foot tall now and are very strong. I am wondering if I should buy a tester and start regulating PH or just keep ignoring it like I am doing now?

Click to expand...

If you want to ignore ph go ahead. You can also ignore yield.
If you are fine with that, it's all good.

I would flower now, because your lights are not strong enough for bigger plants.

If that doesn't make sense to you, try reading this site's grow faq
members like mogie have put a lot of effort into it.

Cheers!https://www.rollitup.org/members/mogie.html

mogie = semi-god status in growtown.