How to Rectify Air Quality Issues in an Indoor Garden 

The primary factors that contribute to the success or failure of an indoor garden are light, grow mediums, nutrients, and air quality. In planning our troubleshooting an indoor garden operation, it is an all-too-common mistake for novice gardeners to focus on the first three elements and neglect the last: air quality. However, finding an ideal equilibrium of air quality in a indoor garden—mainly concerning temperature and humidity—is essential in the propagation of both quality and bountiful harvests. With meticulous attention to detail, indoor growers can create systems that alleviate concerns with air borne pathogens while ensuring efficiency with irrigation and nutrient uptake.

As the indoor gardening industry continues to evolve, it brings with it an ever-expanding assortment of cultivation technology that assist in grow room design. Most notably, there are a variety of digital environmental controls on the market today—these devices automatically control all variants related to air quality in an indoor garden. These controllers accomplish this feat by communicating, electronically, with every piece of equipment in a grow room that dictates temperature and humidity.

Whether an agronomist chooses to regulate the air quality in their indoor garden with less-sophisticated apparatuses, such as timers, or opts with novel environmental controls, the end game is the same: ideal growing conditions for plants. With these notions in mind, here is a brief overview of common air quality issues seen in controlled environment agriculture operations:

indoor garden

Temperature, Humidity, and Environmental Controls 

The proper regulation of both temperature and humidity in a grow room is the most important consideration to be made in ensuring quality air for a CEA garden. Generally speaking, if a garden’s temperature and humidity levels are off, the situation will render all other troubleshooting efforts useless—regarding air flow issues as well as disease.

Maintaining ideal temperatures in a grow room can prove to be a challenge due to a variety of factors—these can all be attributed to temperature fluctuations from outdoor stimuli as well as “day” and “night” cycles within the room. For the most part, indoor gardeners should strive for a temperature range between 75 – 80 deg. F with the lights on (day). Along this line of thought, growers should strive to avoid extreme temperature drops in their rooms when the lights turn off (night)—as this instability can retard growth as well cause issues with dew point and pathogens.

Different geographical locations pose different problems with temperature control in a grow room. However, most indoor growers find an excess of heat to be the largest obstacle to overcome in temperature regulation. There a variety of equipment options on the market for rectifying heat issues in one’s grow room—they are all related to controlling either ambient room temperature of excess heat from grow lights (see below).

Depending on the locale of an indoor garden, most air-quality issues come about as an excess of humidity. Moreover, if one is running a ebb and flow hydroponics system, the presence of standing water in tables and reservoirs greatly increases the relative humidity in a room.

There are a variety of reasons as to why growers must maintain proper humidity levels in their grow rooms. For the most part, properly indoor gardenbalanced humidity in a indoor garden helps plants combat air borne pathogens as well as ensures appropriate nutrient uptake. To illustrate, both powdery mildew and botrytis thrive in poorly ventilated, humid conditions. Also, if immersed in overly humid conditions, plants tend to pull water directly from the air instead of “drinking” through their root systems—this phenomenon can cause a number of issues with both overwatering and malnutrition.

Air quality issues relating to excess humidity can be rectified with proper ventilation and air exchange (see below) as well as with dehumidifiers.

Macro and Micro Air Exchange in an Indoor Garden 

Macro air exchange involves the consistent control of ambient air quality in a indoor garden throughout a crop’s lifecycle. To this end, expert growers recommend that the air in a grow room should be entirely exchanged every 1 to 3 minutes for optimum growth and vigor. There are a couple different equipment options available that can be utilized to ensure efficient air exchange in a room: intake / outtake systems and air conditioning. When properly utilized, these tools can help ensure proper balances of both temperature and humidity.

The use of an intake / outtake air-exchange in an indoor grow is the most traditional, as well as affordable, method for maintaining an optimal equilibrium of air quality in a grow room. Essentially, these rooms are equipped with large inline fans that pull humid, hot air out of the room through ducting, as well as pull fresh air into the room. If properly balanced, and depending on the season and geography in question, this system should rectify most issues with heat and humidity in one’s indoor garden.

The use of mini-split and industrial A/C’s in regulating air quality issues is on the rise within the indoor gardening community—this notion is due primarily to an upsurge in sealed room growing. With the sealed room methodology, it is essentially up to the A/C unit to pull humidity from the air as well as regulate temperature. However, these grow rooms necessitate the use of a CO2 injection system to supplement the CO2 rich air that is brought in with the traditional intake system.indoor garden

Finally, micro air flow refers the movement of air within a grow room that functions independent of the macro-air exchange system in place. Generally speaking, micro-air flow in a grow room is regulated by way of wall fans; these fans ensure that air from intakes, A/C systems, and CO2 devices is evenly distributed around the grow room. Moreover, they resolve issues with “dead pockets” of air within indoor gardens. Dead air pockets leave portions of a garden’s canopy susceptible to pathogens due to lack of air circulation.


Controlling air quality in a grow room is a carefully balanced affair—it requires a harmonious balance of equipment, infrastructure, and troubleshooting. Most importantly, all of these components must work in unison to address temperature and humidity levels in a garden. Once these core elements are addressed, cultivators can comfortably move forward alleviating less-pressing concerns with dead air pockets, CO2, etc. In the end, proper air quality will allow plants to utilize nutrients and light more efficiently, adding overall value to an indoor cultivation operation.


This article originally appeared in the December 2017 edition of Maximum Yield Magazine.