The last use for fans is to encourage sturdy growth. Exercise fans will keep your plants healthy and their branches firm and strong. Keep your exercise and vent fans running 24 hours a day unless you are supplementing with CO2, in which case use a timer to turn the vent fans off when the CO2 gas is turned on. I don’t recommend the use of CO2 in non-commercial gardens. The heat buildup in the room and the aggravation of lugging heavy CO2 tanks around are not worth the gains.
Vented Lamp Hoods
You can use vented light shades (hoods) to cool down a grow room in addition to vent fans. These airtight hoods enclose the top and sides of the lamp in aluminum and the side beneath the lightbulb with glass. Vent hoods are an inexpensive and efficient way to remove heat from a grow room, and they protect growers from the powerful lights that can cause serious burns. If there is only one 1,000-watt halide or sodium lightbulb in your grow room, you might not require anything more than one vent fan. In the case of a two-lamp 1,000-watt lighting system in a typical 12’ × 16’ room, you’ll need a vented hood for each lamp. The air inside the hood is vented through a 4” hose to anywhere outside the garden. A similar hose is positioned at the opposite side of the light hood and runs to another location outside the grow room, pulling fresh, cool air through the hood to cool the lamp. Because cooling air is drawn from outside of the grow room and runs through the sealed hooded lamp system, the exhaust has no odor. Very little heat escapes into the grow room from one of these vented lamp hoods, and you can actually touch the glass under the hood while the lamp is on without burning your hand.
If you don’t have a vented hood, I strongly advise you to turn off your grow lights when working in your indoor garden to protect against skin burns and eye damage from exploding lightbulbs. An accidental spray of cold water on a hot grow lamp can easily explode the bulb and send glass shards flying through the air. Even with vented hoods, you should really use a 100-watt light in the grow room for everyday garden work. Although the grow lights should be turned off during regular garden maintenance, they should definitely be left on when you wish to check your plants for insect damage. Such damage is much easier to see under the bright grow lights. If there are pests in your room, they often end up dead in a little pile lying on the glass inside your hooded grow lights. The evidence of these dead pests is often the first sign of an infestation.
There is a slight loss of brightness while using hood vents because the light has to pass through the glass before contacting the plants. However, I strongly suggest that you use a vented hood system. The safety and convenience of hood vents are worth any minimal loss in lamp brightness.
Air Purifiers
When odor is a problem, you can use an ozone generator (a small appliance available at a hydroponics store) or air purifiers, available in many varieties with more innovative designs arriving on store shelves every day. Your local hydroponics store is the place to start researching the latest and greatest in odor control. The Internet is also a great resource for finding new products.
A simple yet effective way to manage odors in a grow room is with a vented collection chamber and an ozone generator. The collection chamber can be made using a 30-gallon garbage can. To make this DIY air purifier, you’ll need:
• plastic or rubber 30-gallon garbage can with a lid
• jigsaw or bladed cutting device
• 4” flexible dryer hose (long enough to reach from your chamber to your vent exit hole)
• ozone generator
• duct tape
• picture hanging wire
• 2” swag hooks
Then follow these simple steps:
1. Cut a 4” hole in the center of the bottom of the garbage can.
2. Screw the garbage can lid in place and cut a similar 4” hole in the lid.
3. Push a 4” flexible dryer hose into the hole in the bottom of the garbage can.
4. Attach the other end of the hose to a vent fan that pushes air through the 4” diameter exit hole in your grow room.
5. Use duct tape to attach vent ducting and to seal venting system connections.
6. Hang the garbage can horizontally near the ceiling using wires and swag hooks.
7. Insert an ozone generator through the 4” opening in the garbage can lid.
8. Plug the appliance in.
The collection chamber will vent the warm air at the top of the room and mix it with the ozone. The vented air will now smell of ozone, not skunk weed, and neighbors won’t be alerted to the aromas of your grow room. Because ozone generators are harmful to plants (and humans), it is best to vent the exhaust outside of the house and keep the vent fan attached to the collection chamber running at all times. If the vent fan stops working, ozonated air will flow out of the chamber and damage the plants.
A charcoal filter can also be used to combat exhaust odor. Attach the charcoal filter to the ceiling with wire and swag hooks and connect it with 4” dryer hose to a vent fan that pushes air out through a 4” hole in the grow-room wall. Charcoal filters are totally safe for both people and plants and are highly effective in removing odors. Replace your charcoal air filter once a year.
Timers
The lamps in your budding room should be turned on every day for 12 hours and then turned off for 12 hours. This is done simply with a 24-hour timer (available for about $25 at hardware or hydroponics stores). Set your timer so the lights are on during the time period you most want to work in your grow room. Outside the room, it can be day or night. As far as the plants are concerned, when the lights are off it is night, and when the lights are on it is day. Do not turn on any other light during the budding room’s 12-hour periods of darkness because doing so might trigger the budding plants to return to a vegetative state. (I have made this mistake several times, and my budding plants did not revert to vegetative growth, but it can and will happen if a small light is left on for days or weeks during the budding room’s 12-hour dark period.) If you accidently leave your budding lights on too long for any length of time up to a week, just make certain that they return to a regimen of 12-hour dark periods and your plants should suffer no permanent damage.
The lights in your vegetative room can be left on for 24 hours day after day without need of a timer. If you find that the lights in the vegetative room are generating too much heat, set a timer so the lights are on for 18 hours and off for six hours during every 24-hour period. That will allow the room to cool down somewhat for at least six hours every day without affecting the plant’s growth and internal clock. Usually, the lights in the vegetative room are 400-watt halides that run a bit cooler than the 1,000-watt lights in the budding room, but since the vegetative room is often smaller it can still get quite hot.
Timers for both the 400-watt and the 1,000-watt halide and sodium lamps must be heavy-duty models and should be rated for at least 1,200 watts of power draw. Hydroponics stores will sell you the right type of timer, but if you decide to purchase a timer at a hardware store, pick one rated for 1,200 watts or better. If ever you experience a problem with the lighting system (lights that won’t turn on or lights that turn on sooner or later than they should), check the timer first. As they age, timers sometimes burn out and either fail completely or start to run slow. If you see evidence of blackening, burning, or soot where the timer plugs into the wall outlet or at the connections where the light system plugs into the timer, throw it out and buy a new one. Same thing if it becomes noisy or starts to feel warm to the touch. Plan to replace a timer every few years or so.