Editor's note: This article has been reviewed and updated for accuracy in 2026. As an indoor grower, one thing that should never escape your mind is the ventilation of the grow room. Many indoor growers fail to recognize the importance of proper ventilation to their crops, and this leads to poor returns from their hard work. Whether you are using grow tents, cabinet room, or any other form of grow-room, keeping a stable environment is the surest way of getting good returns and avoid things like mold or mildew which can ruin an entire crop. Why Indoor Grows Need Fans Cannabis plants absorb all of the Co2 available around them within around one minute, which is why you’ll need to set up fans near your plants; they distribute any new air around the grow room so that all of your plants have access to a constant stream of Co2 and so that your plants aren’t affected by stagnant air, which can cause illnesses and humidity. With just a little extra airflow, your plants will be able to breathe much better, improving photosynthesis, nutrient absorption and generally increasing your plants’ strength; the branches will grow stronger thanks to the slight wind resistance, which means that during the flowering period they’ll be able to grow thicker, heftier flowers. At the same time expelling the air inside will keep temperature and moisture build-up under control, preventing mold and mildew from forming on your plant's leaves, inhibiting growth. Refreshing the air inside has the added benefit of removing strong odors. For more on air circulation and other guides to learning how to cultivate cannabis like a champ, check out our step-by-step guide to learning and growing as a cultivator. Understanding Most Common Fan Types A variety of fans exists, and each type serves its purpose. Jus