How to Choose Fans and Carbon Filters for Indoor Growing? A Complete Technical Guide

Ventilation and air filtration are fundamental elements of any professional indoor cultivation system. Properly selected and installed devices ensure optimal conditions for plants, control temperature and humidity, and effectively neutralize unwanted odors.

Theoretical Basics of Ventilation

Why is Ventilation Key?

Plants grown indoors require constant air exchange for several key reasons:

• Temperature control – removes excess heat generated by lighting

• Humidity regulation – prevents the development of mold and fungal diseases

• Supplying fresh CO₂ – essential for photosynthesis

• Odor neutralization – discretion and user comfort

• Strengthening stems – gentle air movement stimulates natural growth

Basic Technical Parameters

Air exchange – the minimum recommended air change frequency in a grow room should be 20-40 times per hour (every 1.5–3 minutes).

Room volume – calculated as:
V=L×W×HV = L \times W \times HV=L×W×H  
where V = volume (m³), L = length, W = width, H = height

Required fan performance:
Q=V×nQ = V \times nQ=V×n  
where Q = performance (m³/h), V = room volume (m³), n = number of air changes per hour (20–40)

Types of Fans and Their Characteristics

Axial Fans

Advantages:

• Low noise level

• Low energy consumption

• Easy installation

• Affordable price

Disadvantages:

• Lower static pressure

• Less effective against high flow resistance

Use: Small and medium grow rooms up to 10 m³

Centrifugal (Radial) Fans

Advantages:

• High static pressure

• Efficient with high resistance

• Can work with long duct runs

Disadvantages:

• Higher noise level

• Greater energy consumption

• Higher price

Use: Large installations, long ducts, high resistance

Technical Parameters of Fans

Carbon Filters – Technology and Application

Principle of Operation

Carbon filters use physical adsorption – odor particles adhere to the surface of activated carbon due to van der Waals forces. Activated carbon has a huge specific surface area (500–1500 m²/g).

Types of Activated Carbon

Coconut shell carbon:

• Highest quality

• Lasts 12–18 months

• Superior adsorption effectiveness

Wood-based carbon:

• Medium quality

• 6–12 months lifespan

• Lower price

Bituminous coal carbon:

• Lowest quality

• Short lifespan (3–6 months)

• Cheapest

Parameters of Carbon Filters

Equipment Selection – Formulas and Calculations

Step 1: Calculate Room Volume

For a 2.4m × 1.2m × 2.0m room:
V=2.4×1.2×2.0=5.76 m3V = 2.4 \times 1.2 \times 2.0 = 5.76 \, \text{m}³V=2.4×1.2×2.0=5.76m3

Step 2: Determine Required Performance

With 30 air exchanges per hour:
Q=5.76×30=172.8 m3/hQ = 5.76 \times 30 = 172.8 \, \text{m}³/\text{h}Q=5.76×30=172.8m3/h

Recommended with a safety margin: 200–250 m³/h

Step 3: Account for Flow Resistance

Basic resistances:

• Carbon filter: 50–150 Pa

• Ducts: 10–30 Pa/m

• Elbows and bends: 20–50 Pa/each

• Vents: 20–40 Pa

Example total resistance:

• Filter: 100 Pa

• 2 m duct: 40 Pa

• Two 90° elbows: 60 Pa

• Vent: 30 Pa

• Sum: 230 Pa

Step 4: Select the Fan

The fan must provide 200-250 m³/h at 230 Pa resistance.

Technical Solutions and Installation

Schematic 1: Basic Setup

1. Air from the grow room

2. Intake fan

3. Carbon filter

4. Exhaust fan

5. To the outside

Schematic 2: Optimal Setup

1. Air is drawn from the room through the carbon filter

2. Then passes to the exhaust fan

3. Optionally through a silencer

4. Directed outside

5. Additionally, an internal circulation fan ensures air movement around the plants

Installing the Carbon Filter

Filter Position:

• Inside the room – best effectiveness

• Outside – saves space, but less effective

Orientation:

• Vertical – optimal for most filters

• Horizontal – allowed if properly supported

Connections:

• Aluminum or PVC ducts

• Stainless steel clamps

• Rubber gaskets at connections

Controls and Automation

Basic controllers:

• Thermostat – temperature control

• Hygrostat – humidity control

• Timer – programming cycles

Advanced controllers:

• Climate controllers with sensors

• PID controllers

• Smart home systems

Leading Manufacturers of Ventilation Equipment

Fans

Soler & Palau (Spain)

• Series: TD Silent, Mixvent

• Features: high quality, quiet operation

• Price: mid-high

S&P (Systemair)

• Series: RVK, K-Line

• Features: professional, durable

• Price: high

Vents (Ukraine/Germany)

• Series: VKO, VKOM, TT

• Features: good price-to-quality ratio

• Price: medium

Blauberg (Germany)

• Series: Turbo, Centro, Iso-Mix

• Features: modern design, efficient

• Price: mid-high

Carbon Filters

Can-Filters (Canada)

• Series: Can-Original, Can-Lite

• Features: coconut carbon, long lifespan

• Price: high

Prima Klima (Czech Republic)

• Series: K2600, ECO

• Features: good price-to-quality ratio

• Price: medium

PhreshFilters (USA)

• Series: Phresh Filter

• Features: coconut carbon, compact

• Price: mid-high

Rhino Pro (UK)

• Series: Rhino Pro Carbon Filter

• Features: high quality, various sizes

• Price: medium

Example Sets for Different Room Sizes

Small Room Set (up to 3 m³)

Fan: Vents TT 125mm – 220 m³/h
Filter: Prima Klima K2600 150mm – 240 m³/h
Ducts: 125mm Aluminum, 2 m
Cost: ~600–800 PLN

Medium Room Set (3–8 m³)

Fan: S&P TD-350/125 Silent – 350 m³/h
Filter: Can-Lite 425 m³/h
Ducts: 125mm Aluminum, 3 m
Controllers: Thermostat + Hygrostat
Cost: ~1200–1500 PLN

Large Room Set (8–15 m³)

Fan: Systemair RVK 150mm – 470 m³/h
Filter: Phresh Filter 500 m³/h
Ducts: 150mm insulated, 4 m
Controller: GSE climate controller
Cost: ~2000–2500 PLN

Maintenance and Servicing

Fans

• Clean every 3 months

• Replace bearings every 2–3 years

• Check electrical connections

Carbon filters

• Check efficiency monthly

• Replace carbon every 12–18 months

• Clean pre-filter every 2 weeks

Ducts and Connections

• Check for leaks every 6 months

• Clean interior annually

• Replace when damaged

Most Common Mistakes and How to Avoid Them

Undersized capacity

• Always include a 20–30% safety margin

• Take reduced efficiency over time into account

Incorrect installation

• Avoid long, winding duct runs

• Support heavy filters properly

Neglecting maintenance

• Check and clean equipment regularly

• Don’t delay replacing worn-out parts

False economy

• Don’t skimp on the carbon filter quality – it’s foundational

• Cheap equipment can cause higher operating costs long-term

Properly selected and installed ventilation with carbon filtration is an investment in the long-term success of any indoor grow. By following the above tips and choosing reputable manufacturers, you guarantee yourself years of reliable system performance.