The proposed Bio-Breezer is designed as a simple, low-cost, and energy-efficient herbal filtration unit for integration into the Bio-Breathing Herbal Air Cooling System. The system combines activated carbon adsorption, herbal biofiltration, evaporative cooling, and real-time environmental monitoring to improve indoor air quality. A quality plastic vegetable rack can be repurposed as a multi-layer filtration chamber because it provides multiple perforated trays that support filtration media while allowing uniform airflow. This approach significantly reduces fabrication cost and simplifies system assembly.

Materials Required

• Mechanical Components
• 3- or 4-tier plastic vegetable rack (perforated trays)
• 12 V DC blower fan (120–150 mm)
• Acrylic sheet or plywood (base plate and front door)
• Fine nylon mesh
• Cable ties
• Silicone sealant
• Screws and mounting brackets
   

Filtration Materials

• Activated charcoal granules
• Dried medicinal herbs:
   
• Tulsi (Ocimum tenuiflorum)
• Neem (Azadirachta indica)
• Mint (Mentha)
• Eucalyptus
• Lemongrass (Cymbopogon citratus)
• Cooling pad (Khus/Vetiver, cellulose pad, or cotton pad)
   

Electronic Components

• Arduino Leonardo
• MQ-135 Air Quality Sensor
• DHT22 Temperature and Humidity Sensor
• L298N Motor Driver Module (for DC blower speed control)
• 16×2 LCD Display with I²C interface
• 12 V DC power adapter
• Connecting wires and jumper cables
   

Step 1: Prepare the Vegetable Rack
Clean the plastic vegetable rack thoroughly to remove dust and contaminants. Inspect the rack to ensure that each tray is securely positioned and that the spacing between adjacent trays is approximately 50–70 mm, providing sufficient space for the filtration media.
 

Purpose:
To provide a lightweight, durable, and reusable enclosure for arranging multiple filtration layers.
 

Step 2: Prepare the Base
Fabricate a rigid base using acrylic sheet or plywood. Cut a circular opening at the center corresponding to the diameter of the DC blower fan. Securely mount the vegetable rack on the base and seal any gaps using silicone sealant.
Purpose:
To provide mechanical support and create an air inlet for the blower.
 

Step 3: Install the DC Blower Fan
Mount the 12 V DC blower fan beneath the base using screws or brackets. Ensure that the blower is oriented to push air vertically upward into the filtration chamber. Connect the blower to the L298N motor driver module, which is controlled by the Arduino Leonardo. This enables automatic adjustment of blower speed according to the measured air quality and environmental conditions.
Purpose:
To generate continuous airflow through all filtration layers and provide controlled air circulation.
 

Step 4: Construct the Activated Charcoal Layer
Cover the lowest tray with a fine nylon mesh to prevent charcoal particles from falling through the perforations. Spread activated charcoal granules uniformly over the tray. Recommended thickness: 40–60 mm
Function:
Adsorbs volatile organic compounds (VOCs)
Removes unpleasant odors
Reduces smoke and harmful gaseous pollutants
 

Step 5: Construct the Herbal Filtration Layer
Place another nylon mesh over the middle tray and fill it with a uniformly distributed mixture of dried medicinal herbs, including:
Tulsi, Neem, Mint, Lemongrass, Eucalyptus
The herbal materials should be loosely packed to minimize airflow resistance while maximizing air contact. Recommended thickness: 50–70 mm
Function:
Provides natural herbal fragrance
May contribute to reducing microbial growth
Enhances indoor breathing comfort
Supports eco-friendly air purification
 

Step 6: Construct the Cooling Layer
Install a nylon mesh on the upper tray and place the cooling material over it.
Suitable cooling media include:
Khus (Vetiver) pad
Cellulose cooling pad
Cotton cooling pad
For evaporative cooling, lightly moisten the cooling pad using a small water reservoir or drip arrangement. Recommended thickness: 30–50 mm
Function:
Reduces outlet air temperature through evaporative cooling
Improves thermal comfort
Maintains adequate moisture within the airflow
 

Step 7: Install the Enclosure
Attach acrylic sheets around the sides of the vegetable rack to create an enclosed filtration chamber. Provide a hinged acrylic front door to facilitate replacement and maintenance of the filtration media. Install a perforated acrylic cover or mesh at the top to serve as the purified air outlet. Seal all unwanted openings using silicone sealant to prevent air leakage.
Purpose:
To ensure that all incoming air passes through each filtration layer before exiting the system.
 

Step 8: Install the Environmental Sensors
Mount the MQ-135 Air Quality Sensor and DHT22 Temperature and Humidity Sensor near the purified air outlet.
Position the sensors away from the wet cooling pad to avoid inaccurate readings caused by direct moisture exposure.
Purpose:
To continuously monitor indoor air quality, temperature, and relative humidity.
 

Step 9: Install the Arduino-Based Monitoring System
Connect the MQ-135 sensor, DHT22 sensor, LCD display, and L298N motor driver module to the Arduino Leonardo according to the circuit diagram. Upload the Arduino program to perform the following operations:
Acquire sensor data
Calculate air quality status
Display temperature, humidity, and air quality on the LCD
Automatically regulate blower speed based on air quality
 

Step 10: Test and Validate the System
Switch on the power supply and observe the airflow through the Bio-Breezer. Verify that:
Air flows uniformly from the bottom to the top.
Sensor readings are correctly displayed on the LCD.
The blower speed changes appropriately according to the measured air quality.
No significant air leakage exists around the enclosure.
The filtration layers remain securely positioned during operation.

Working Principle
The Bio-Breezer operates using a bottom-to-top forced-air filtration mechanism. The DC blower fan draws polluted indoor air through the bottom air inlet and forces it upward through three sequential filtration stages.
First, the activated charcoal layer adsorbs volatile organic compounds (VOCs), smoke particles, odors, and harmful gaseous pollutants. 

The partially purified air then passes through the herbal filtration layer, where medicinal herbs release natural volatile compounds that provide a pleasant aroma and may contribute to reducing microbial growth. Finally, the air passes through the evaporative cooling layer, where the cooling pad lowers the outlet air temperature while maintaining comfortable humidity levels.
 

The MQ-135 and DHT22 sensors continuously monitor air quality, temperature, and humidity. The Arduino Leonardo processes these sensor measurements, displays the environmental parameters on the LCD, and regulates the blower speed through the L298N motor driver module. The purified and cooled air is then discharged through the top outlet, providing a sustainable and energy-efficient solution for improving indoor environmental quality.