Intake Fan

The intake fan is the partner to the exhaust fan in a balanced grow room ventilation system, providing fresh air to replace what's being exhausted. Active vs passive intake: (1) Passive intake — small grow tents (under 4×4 ft) typically use passive intake through mesh vents at the bottom of the tent; the negative pressure created by the exhaust fan naturally draws air in through the vents; no powered intake fan needed; this approach is simple and works well for small spaces. (2) Active intake — larger rooms and commercial operations use powered intake fans to ensure adequate fresh air delivery; active intake provides better airflow control, allows filtering of incoming air through HEPA filters for pest control, and maintains consistent room pressure. Sizing calculation: intake fan CFM should be 60-80% of exhaust fan CFM to maintain slight negative pressure (negative pressure ensures any air leaks flow inward rather than outward, preventing odor escape from grow rooms); for a room with 800 CFM exhaust, install 480-640 CFM intake. Intake placement: install at the bottom of the grow space (cool fresh air is denser and naturally falls); position far from exhaust outlets to prevent recycling stale air; ducting should run through cool spaces (basement, north-side rooms) for cooler air supply; consider HEPA filtering for incoming air if outside air carries pests, dust, or pollen. Air source quality: drawing from inside the home recycles already-conditioned air (cool in summer, warm in winter) saving energy but doesn't introduce fresh CO2; drawing from outside provides fresh CO2 (essential for non-CO2-supplemented grows) but requires temperature management; sealed CO2 grow rooms eliminate intake entirely, recirculating internal air with controlled CO2 supplementation. Filtration considerations: pollen and dust filters protect indoor cultivation from outdoor contamination; HEPA filtration (0.3 micron rated) prevents pest introduction during the most vulnerable seedling and clone stages; activated carbon pre-filters can remove smoke or chemical odors from outdoor air. Intake fan controllers: smart controllers (AC Infinity Controller 69 Pro, TrolMaster) can synchronize intake and exhaust fan speeds based on environmental conditions, maintaining optimal pressure differential and air exchange rates automatically. For most home cannabis tents (4×4 ft and smaller), passive intake through mesh vents is sufficient; active intake becomes important for larger rooms (5×5 ft+) and any operation requiring strict pest control or sealed CO2 supplementation.