Air quality is one of the most overlooked aspects of indoor horticulture. Even growers with adequate ventilation systems may be negatively affected by the air quality in their growroom. Ventilation systems are essentially designed to remove stale air from the garden space and replace it with fresh air from the outside, however, basic ventilation systems do not always safeguard an indoor garden from various problems that may arise due to poor air quality.

A ventilation system is a way to keep the garden cool and replenish the CO2 needed by the plants for photosynthesis. However, in addition to cooling and replenishing CO2, a ventilation system should also provide the proper filtration or purification measures needed to ensure good air quality.

In fact, purifying or filtering the air for a growroom is much like purifying or filtering water for a growroom. In both cases a grower implements equipment and procedures that will increase the quality and thus improve the overall conditions of the garden. Without adequate air filtration or purification, a grower may open the door for a wide variety of problems.

Fungi Spores and Molds

A lot of the pathogenic molds and fungi that can infect an indoor garden are transmitted through the air. A few examples of destructive fungi that are transmitted through the air are powdery mildew, black spot and botrytis. When given the right conditions, these opportunist fungi quickly cause problems to otherwise healthy plants and can destroy an entire crop in a short period of time.

Since the spores of these fungi are invisible to the naked eye they are often overlooked by new indoor horticulturists. If a crop contracts one of these destructive fungi, it takes serious work to eradicate the issue entirely. As with most problems in an indoor garden, prevention is key.

Pest Insects

The dreaded spider mite (arguably the most destructive pest insect for indoor horticulturists) creates a small strand of webbing that acts very much like a parachute, allowing it to relocate via the wind. Unsuspecting gardeners inadvertently introduce these monstrous pest insects into their growrooms through their ventilation systems. Again, prevention is the best defense against spider mites and other pest insects that can be introduced through the fresh air intake of a ventilation system.

How to Maintain Growroom Air Quality

Bacteria

Although not nearly as common as molds and fungi, airborne bacteria can also cause problems for certain indoor crops. Bacterial infections can cause a variety of symptoms, including blights, cankers, galls, leaf spots, overgrowths, specks, scabs or wilts. Bacterial infections are usually hard to identify and more often than not they are misdiagnosed as a nutrient deficiency. Eliminating airborne bacteria before they affect the plants is the only realistic defense.

Pollen

Unwanted pollen in the air can cause problems for indoor horticulturists. Cross-contamination of species can ruin an entire crop, especially if the grower is attempting to perform controlled breeding. Some annual plants, peppers for example, can be cross-pollinated, which creates unstable offspring. For many seed producers, it is imperative to keep similar species’ pollen separate from each other to avoid cross-contamination.

Volatile Organic Compounds (VOCs) and Odors

Volatile organic compounds (VOCs) are chemical compounds (gases) found in the air. Indoor gardens can produce a variety of odors, from fertilizer smells to plant odors. These odors are all types of VOCs. Although most odors are more of a nuisance than a detriment, some VOCs, like the ones left behind by chemical insecticides or fungicides, can be dangerous. Air purification is the only way to eliminate VOCs and reduce odors in and around an indoor garden.

Implementing an Air Purification Device

Once a horticulturist understands the importance of maintaining a high air quality in the garden, he or she will take the necessary precautions to purify the air. Indoor gardeners who implement air purification devices and techniques will decrease the likelihood of pathogens, pollens and VOCs found in the air and automatically create a better environment for the plants.

There are many different air purification devices available, each with its own advantages and disadvantages. Three of the most common devices used for maintaining air quality in the garden are intake filters, stand-alone filters and air purifiers.

Intake Filters

Intake filters are important preventive tools that just about every indoor gardener should have included in his or her ventilation system. Intake filters can vary greatly, but they all have a common goal: to allow maximum airflow while still effectively filtering as much as possible. Perhaps the best examples of this are high-efficiency particulate air (HEPA) filters. HEPA filters are able to remove particles in the air down to .3 microns in size. Many mold spores fall in the 1-20 micron size, which means HEPA filters are a good choice for preventative protection against mold spores.

Even on “closed” air-cooled systems, intake filters can greatly help a garden’s performance. Although air filtration is not really considered a lighting issue, it can affect the lighting system in an indoor garden. When dirt and dust settle on the reflector’s glass, it significantly reduces the efficiency of the lighting system. If a grower filters the air before it enters the air-cooling system, they can greatly reduce the sediment build-up on the reflectors and keep the light levels as high as possible.

Stand-alone Filters

Stand-alone filters are filters (combined with a fan) that are used within the garden space. The purpose of a stand-alone filter is to continuously recirculate the air within the garden space and filter it in the process. The type of filters most commonly used for this application are carbon filters. Implementing a stand-alone filter is not only a great way to reduce or eliminate odors, but it will also help to reduce the likelihood of mold problems.

Air Purifiers

Air purifiers are specific devices that recirculate the air within a garden and purify it. Most growers implement an air purifier in addition to an intake or stand-alone filter. The main purpose of an air purifier is to eliminate any mold spores, bacteria or VOCs floating around the garden space. An air purifier is a great addition to any indoor garden, however, not all air purifiers are the same.

HEPA Air Purifiers

Some air purifiers on the market are simply HEPA filters equipped with a low-powered fan. This type of air purifier would be ok for an indoor garden the size of a closet. A gardener who is considering using one of these filters in a larger space would probably be better off opting for an inline fan and HEPA filter combo.

How to Maintain Growroom Air Quality

Ozone Air Purifiers

Another type of air purifier on the market are ozone-based air purifiers. These devices usually have a UV light to produce ozone and a fan to circulate the air. Ozone air purifiers should be considered carefully by most growers because they may produce detectable ozone within the garden space. Accumulated ozone in a garden space can damage plants and be harmful to humans.

Photocatalytic Air Purifiers

Growers looking for a top-of-the-line air purification device should choose a photocatalytic air purification system. These air purifiers are not inexpensive, but they are the most effective at maintaining a high level of air quality. Photocatalytic air purifiers use specialized catalysts that, with the help of some UV light, create powerful oxidizers.

As the air is circulated through the air purifier, the oxidizers destroy the molds, bacteria, etc. Unlike ozone-based purifiers, which use UV light to produce ozone, the high-quality photocatalytic air purifiers will produce no detectable ozone. As the cost of photocatalytic air purification systems goes down, I believe more indoor horticulturists will use them as a line of defense against pathogens and as a way to maintain the highest level of air quality possible.

Conclusion

Maintaining a high level of air quality is important when trying to provide plants with optimal growing conditions and also for preventing unwanted issues. Growers who invest in air filtration devices or air purification devices can rest assured that their gardens are protected from many of the unseen pathogens lurking in the air.

Pathogenic fungi and pest insects can quickly turn an otherwise healthy garden into mush in a couple of days. The growers who understand the importance of preventing problems before they occur are the gardeners who will receive larger returns on their investments. One of the best ways to stop problems before they occur is to implement an air filtration and/or air purification system in an indoor garden. A healthy exchange of clean, fresh air in a growroom can mean the difference between utter failure and raving success.