You do need fresh air. I have a fan controler that I set the temperature at 76 degrees. When the room hits 76 degrees the fan kicks on and brings in fresh cool air from outside the room. The fan stops when the room is at 73 degrees and the room starts to heat again from heat from a small radiator type heater. This keeps the fan comming on about every half hour. Also you need a oscalating fan blowing in the room. This will strengthen the stems and help them breath....as well it helps to dry the soil a little faster and plants like the drying soil. The roots love oxygen see....you should be mixing big chunky perlight into the soil about 25 percent perlight and 75 %soil. This will help the plants drain water well and provides oxygen in the soil. Also the soil dries out quicker which helps the roots grow. I use Smart Pots which are made from a felt like material. They allow the pots to dry quicker and there is less chance of anerobic conditions developeing from lack of oxygen and standing water in the bottom of the pots. Hell you can even put in a layer of perlight 3/4 an inch deep in the bottom of the pots if ya want...this is on your first grow only though....until you get a feel for watering correctly and know when they need water. 75% at least....of new growers kill or stunt their plants by overwatering or over fertilizing. Foxfarms soil has enuff fertilizer in it for 30 days or more. With marijuana less is by far better when it comes to feeding them. Alot of new growers fall to the shiny labeled bottles of expensive fertilizer at the grow shops. And the guy behind the counter gets paid well to push these expensive bottles of snake oil.
A little about soil and how I do it with great results.
Get yourself a cheap MR Turtle Pool like the kids use in the summer. They work awesome to mix soil in.
Go buy the biggest bag of chunky perlight that you can find...about 30 bucks
Go buy 2 bags of happyfrog and 1 bag of ocean forest.
Dump all 3 bags into the pool
Dump in 20 - 25 % perlight
Add 1/2 cup of pellitized dolomite lime.
Mix this really really well and let it sit uncovered overnight.....then mix it again in the morning and place into a plastic trash can.
You can start seedlings in this if you want....the soil will not be to hot.
OK....heres what I do next
Take the same kiddy pool and make up a batch of supersoil.....heres my recipe modified from subcools recipe which is awesome...... BIG THANKS to Subcool for this. The only thing I change is the soil brands because the roots organic soil quality and consistancy has failed big time...plus the gnats are horrible.
1/2 Batch:
4 bags Organic Base Soil.....I use Happyfrog
12.5-25 lbs. Worm Castings.....This is important....go find a worm farm and buy the castings fresh from the farm. No dried out expensive
bags from the hydro store. I pay 10 bucks for a 5 gallon bucket full and it comes complete with springtails and other critters...really good stuff and the plants love it.
2.5 lbs Fish Bone Meal
2.5 lbs Bat Guano
2.5 lbs Blood Meal
3/8 cup (1/4 cup + 1/8 cup) Epsom Salts
1/2 cup Sweet (dolomite) Lime
1/4 cup Azomite
1 Tbs Powdered Humic Acid
Dont forget the 20 - 30% perlight
Now mix this up really well....let it sit uncovered overnight then mix again then into another plastic trash can and dont use for 1 - 2 months. My supersoil is a year old and I need another batch mixed pretty quick.
Now when I transplant my plants from 1 gallon pots into 5 gallon pots I put about 2 - 5 inches of supersoil in the bottom of each pot depending of the strain.
All I add the entire grow is water and microbial teas....Sometimes a small amount of select organic boosters and mollasas late in flower I only make 2 teas per grow and dont apply the first tea until the roots have been completly growing down into the supersoil and are adult roots. When the microbes in the tea get down there in that rich supersoil something magical happens...really. The roots get massive and the stalks get thick and the plants really hit the gas and start growing like mad...this is when I start flowering the plants...you will get to just know when its time...
I know you did not ask for all this but it should help you and others that may read the thread.
Peace and Pot