1. Importance of Humidity Control

Maintaining proper RH in vegetable cold storage is as critical as temperature control, because moisture loss or gain directly impacts texture and marketability. 

• Low Humidity Risks: When RH drops below optimal levels, vegetables lose turgor, leading to wilting, yellowing, and weight loss that reduce consumer appeal. 

• High Humidity Risks: Excess humidity promotes surface condensation, which fosters mold and bacterial growth and can interfere with refrigeration defrost cycles, causing temperature fluctuations.

2. Vegetable‐Specific Humidity Requirements

Different types of vegetables demand tailored RH settings to maintain their unique quality attributes:

• Leafy Vegetables (e.g., spinach, celery): Require 90 %–95 % RH to prevent leaf desiccation and wilting. 

• Root Vegetables (e.g., carrots, radishes): Also need 90 %–95 % RH to avoid surface cracking and loss of firmness. 

• Fruiting Vegetables (e.g., cucumbers, tomatoes): Best stored at 85 %–90 % RH to preserve firmness and skin integrity without promoting decay. 

Modern vegetable cold rooms employ a combination of systems to achieve and maintain target RH levels:

1. Temperature & Humidity Monitoring Systems:
   High-precision sensors sample every 1–5 minutes, feeding data to central controllers that trigger alarms on deviations. 

2. Automated Humidification/Dehumidification:
   Humidifiers add moisture when RH falls below setpoints, while condensing dehumidifiers remove excess water vapor—both integrated into the HVAC loop for seamless operation. 

3. Optimized Airflow Design:
   Multi-point return and supply air ducts ensure uniform distribution, preventing pockets of high or low humidity and avoiding localized condensation. 

4. Moisture‐Barrier Packaging:
   Controlled‐humidity or modified‐atmosphere packaging films (MA/MH) with tailored moisture vapor transmission rates help stabilize in-package RH and protect sensitive produce.