Few users of plant growth chambers are familiar with the fresh air intake and exhaust ports. Identified below, the fresh air intake allows the operator to manually adjust the rate at which fresh air is introduced into the chamber. The threaded collar is often located on the front of the chamber’s machine compartment and can be adjusted from fully closed (no fresh air) to fully open to allow maximum air exchange. See image below, left:
Air exchange is important in growth chambers to avoid CO2 deficits:
Any discussion of air movement must also consider the need for a fresh air supply, commonly called makeup air. If no provision is made to inject CO2 into the chamber atmosphere to compensate for the CO2 taken up during photosynthesis, then makeup air is helpful, especially in tightly enclosed growth rooms or specially constructed closed chambers where CO2 deficits can easily occur once the canopy becomes dense.1
The fresh air intake assembly often contains a foam filter to help prevent dust and larger particulate matter from entering the growth area. If your unit comes equipped this filter should be cleaned monthly to prevent a build-up of foreign material that could restrict airflow. Fresh air is drawn into the front of the chamber through the intake port, typically by a variable speed fan located in the machine compartment, and then exhausted through the exhaust port. See image above right.
1. Source: Plant Growth Chamber Handbook, edited by R.W. Langhans and T.W. Tibbitts North Central Regional Research Publication No. 340, Iowa Agriculture and Home Economics Experiment Station Special Report No. 99, pg. 94. Original source: Bailey et al., 1970; Krizek et al., 1970.