Ventilation and Odor Control 101

The following is an excerpt from The Insatiable Gardener's Guide: How to Grow Anything & Everything Indoors, Year 'Round by Susan M. Brackney, reprinted by permission of Five Hearts Press:

Taking Charge

For plants living outdoors, getting plenty of fresh air is never a problem because the wind naturally exchanges the air around them. But for plants growing inside? It's up to us to bring the fresh air to them with a combination of circulating fans and simple air exhaust systems. By regularly replacing moist, stale air with drier, fresher air, we stabilize temperature and humidity levels while helping our plants maintain a proper balance of usable carbon dioxide and oxygen. Keeping the air moving also helps stomata (tiny pores in plant leaves that allow exchange of carbon dioxide, oxygen, and water) stay relatively dust-free so plants can breathe with ease.

If your garden room happens to be equipped with a ceiling fan, circulating the air shouldn't be a problem. If you don't have a ceiling fan, one or two oscillating fans should be enough to reunite the warm air, which naturally rises to the ceiling, with the cooler air that's left behind.

But simply mixing and moving the same air around and around isn't quite enough for your plants; you should also ventilate the area. From super-easy to more complex, there are a couple of ways to take care of this. One of the simplest methods is to leave the door to your grow room open as a source of fresh air and then exhaust the stale air with a vent fan mounted in an open window.

You also can install a ventilation duct and in-line exhaust fan in one wall leading through to the outside. You can study how your clothes dryer or stove with an exhaust fan has been vented to get a better idea. If you do put in a special ventilation duct for your indoor garden, it's smart to place it up high since that's where most of the stale, hot air ends up. As the duct fan pulls stale air up and out, fresh air from the rest of the house takes its place.

What's more, it's easy to automate this type of system by hooking the in-line duct fan to a thermostat. With a thermostat-controlled vent, your indoor garden becomes somewhat self-regulating. If, for instance, you've decided you don't want temperatures to climb above 80 degrees F, you can set your duct fan to come on as soon as temperatures exceed your acceptable range.

To keep the environment even cooler—and to prolong the life of your equipment—you can also choose a reflector and ballast with built-in ventilation features. Sunleaves Aurora Six and Sunspot Six Reflectors have these capabilities, as do all Sunleaves Pulsar ballasts. If you already have a reflector and ballast that don't have any of these special features, don't worry. In many cases you can modify standard reflectors and ballasts with ventilation kits.

Aside from using simple thermostats, some indoor gardeners like to take things a step further by connecting humidistats to their vent fans or to dehumidifiers. Just as a thermostat regulates temperature, a humidistat regulates humidity. Want your plants to enjoy a constant 50 percent humidity? With a humidistat-controlled vent or dehumidifier, you can be sure the indoor garden doesn't become too dry or too moist.

Odor Control

The right mixture of high humidity, organic fertilizers, and hydroponics nutrients can turn an otherwise pleasant spot musty in a hurry. Fortunately, there are odor control methods available to eliminate even the funkiest of funks. From simple to state-of-the-art, they range in price and application, but many odor control techniques including ozone generators, carbon filters, ionizers, and natural air fresheners can effectively neutralize the not-so-fresh smells in your greenhouse or home in no time. There's no sense in killing a fly with a sledgehammer; likewise, why use more odor control force than a situation warrants? To that end, we'll start with the light-duty techniques such as natural air fresheners first.

Natural Neutralizers

Natural air fresheners are inexpensive, safe, and come in a variety of forms. Some act as masking agents, but products like Ozium actually neutralize odors by bonding with them on a molecular level. Available in spray, liquid, or gel forms, these methods can be used by themselves or in conjunction with misting systems or humidifiers, which can increase their efficacy. With continued use, neutralizer gels will dry out and lose potency but refill products are available to refresh them. Natural air fresheners and odor neutralizers typically work best in smaller areas.

Ionizers

A very safe and effective choice for long-term odor reduction, ionizers emit negative ions which combine with positively-charged, indoor particles such as dust, mold spores, smoke, pollen, and pet dander to trap and neutralize them. The newly combined positive and negative particles become too heavy to stay airborne and are then easily filtered. Ionizers can discolor walls and surfaces; as such, you'll want to use your ionizer in a well-circulated space and change filters regularly for best results.

Carbon Filters

If you have particularly persistent garden and household odors, activated carbon is yet another excellent means to neutralizing the air. Through a process known as adsorption, activated carbon attracts, bonds, and traps the odor elements through the tons of tiny little pores on its surface. Activated carbon is most effective when packed tightly into a unique type of filter and used in conjunction with a specialized fan to pull the stagnant air through the filter, as is the case with Can Fan Combos. These combos come in several sizes to accommodate different sized areas and can eliminate odors for up to 18 months. The separate fan and filter components are also available individually to create your own customized set-up.

Ozone Generators

Ozone generators like the Uvonair take oxygen from the air, transform some of that oxygen into ozone, and then release the ozone back into the air. Because an ozone molecule is made up of three oxygen atoms, ozone is naturally unstable; each ozone molecule works to release its extra atom to become oxygen again. The atoms released combine with organic compounds in the air changing their chemical makeup and, thus, neutralizing their odors.

When it comes to ozone generators, it's important to note that the popular notion "More is better" doesn't apply. Ozone toxicity in plants looks a lot like a pH imbalance, and plants exposed to too much ozone may exhibit yellowed or pale blotches on leaves. As for the rest of us, prolonged or over exposure to ozone can damage the lungs when inhaled and even cause chest pain, coughing, shortness of breath, and throat irritation. The FDA has set a limit of 0.05 parts per million of ozone in indoor air, and, because too much ozone can be harmful to your plants and you, ozone generators should be used with a timer for safe measure.